1 /*
2 * Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.
3 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
4 *
5 *
6 *
7 *
8 *
9 *
10 *
11 *
12 *
13 *
14 *
15 *
16 *
17 *
18 *
19 *
20 *
21 *
22 *
23 *
24 */
25
26 package java.nio.file;
27
28 import java.io.BufferedReader;
29 import java.io.BufferedWriter;
30 import java.io.Closeable;
31 import java.io.File;
32 import java.io.IOException;
33 import java.io.InputStream;
34 import java.io.InputStreamReader;
35 import java.io.OutputStream;
36 import java.io.OutputStreamWriter;
37 import java.io.Reader;
38 import java.io.UncheckedIOException;
39 import java.io.Writer;
40 import java.nio.channels.Channels;
41 import java.nio.channels.FileChannel;
42 import java.nio.channels.SeekableByteChannel;
43 import java.nio.charset.Charset;
44 import java.nio.charset.CharsetDecoder;
45 import java.nio.charset.CharsetEncoder;
46 import java.nio.charset.StandardCharsets;
47 import java.nio.file.attribute.BasicFileAttributeView;
48 import java.nio.file.attribute.BasicFileAttributes;
49 import java.nio.file.attribute.DosFileAttributes; // javadoc
50 import java.nio.file.attribute.FileAttribute;
51 import java.nio.file.attribute.FileAttributeView;
52 import java.nio.file.attribute.FileOwnerAttributeView;
53 import java.nio.file.attribute.FileStoreAttributeView;
54 import java.nio.file.attribute.FileTime;
55 import java.nio.file.attribute.PosixFileAttributeView;
56 import java.nio.file.attribute.PosixFileAttributes;
57 import java.nio.file.attribute.PosixFilePermission;
58 import java.nio.file.attribute.UserPrincipal;
59 import java.nio.file.spi.FileSystemProvider;
60 import java.nio.file.spi.FileTypeDetector;
61 import java.security.AccessController;
62 import java.security.PrivilegedAction;
63 import java.util.ArrayList;
64 import java.util.Arrays;
65 import java.util.Collections;
66 import java.util.EnumSet;
67 import java.util.HashSet;
68 import java.util.Iterator;
69 import java.util.List;
70 import java.util.Map;
71 import java.util.Objects;
72 import java.util.ServiceLoader;
73 import java.util.Set;
74 import java.util.Spliterator;
75 import java.util.Spliterators;
76 import java.util.function.BiPredicate;
77 import java.util.stream.Stream;
78 import java.util.stream.StreamSupport;
79
80 /**
81 * This class consists exclusively of static methods that operate on files,
82 * directories, or other types of files.
83 *
84 * <p> In most cases, the methods defined here will delegate to the associated
85 * file system provider to perform the file operations.
86 *
87 * @since 1.7
88 */
89
90 public final class Files {
91 private Files() { }
92
93 /**
94 * Returns the {@code FileSystemProvider} to delegate to.
95 */
96 private static FileSystemProvider provider(Path path) {
97 return path.getFileSystem().provider();
98 }
99
100 /**
101 * Convert a Closeable to a Runnable by converting checked IOException
102 * to UncheckedIOException
103 */
104 private static Runnable asUncheckedRunnable(Closeable c) {
105 return () -> {
106 try {
107 c.close();
108 } catch (IOException e) {
109 throw new UncheckedIOException(e);
110 }
111 };
112 }
113
114 // -- File contents --
115
116 /**
117 * Opens a file, returning an input stream to read from the file. The stream
118 * will not be buffered, and is not required to support the {@link
119 * InputStream#mark mark} or {@link InputStream#reset reset} methods. The
120 * stream will be safe for access by multiple concurrent threads. Reading
121 * commences at the beginning of the file. Whether the returned stream is
122 * <i>asynchronously closeable</i> and/or <i>interruptible</i> is highly
123 * file system provider specific and therefore not specified.
124 *
125 * <p> The {@code options} parameter determines how the file is opened.
126 * If no options are present then it is equivalent to opening the file with
127 * the {@link StandardOpenOption#READ READ} option. In addition to the {@code
128 * READ} option, an implementation may also support additional implementation
129 * specific options.
130 *
131 * @param path
132 * the path to the file to open
133 * @param options
134 * options specifying how the file is opened
135 *
136 * @return a new input stream
137 *
138 * @throws IllegalArgumentException
139 * if an invalid combination of options is specified
140 * @throws UnsupportedOperationException
141 * if an unsupported option is specified
142 * @throws IOException
143 * if an I/O error occurs
144 * @throws SecurityException
145 * In the case of the default provider, and a security manager is
146 * installed, the {@link SecurityManager#checkRead(String) checkRead}
147 * method is invoked to check read access to the file.
148 */
149 public static InputStream newInputStream(Path path, OpenOption... options)
150 throws IOException
151 {
152 return provider(path).newInputStream(path, options);
153 }
154
155 /**
156 * Opens or creates a file, returning an output stream that may be used to
157 * write bytes to the file. The resulting stream will not be buffered. The
158 * stream will be safe for access by multiple concurrent threads. Whether
159 * the returned stream is <i>asynchronously closeable</i> and/or
160 * <i>interruptible</i> is highly file system provider specific and
161 * therefore not specified.
162 *
163 * <p> This method opens or creates a file in exactly the manner specified
164 * by the {@link #newByteChannel(Path,Set,FileAttribute[]) newByteChannel}
165 * method with the exception that the {@link StandardOpenOption#READ READ}
166 * option may not be present in the array of options. If no options are
167 * present then this method works as if the {@link StandardOpenOption#CREATE
168 * CREATE}, {@link StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING},
169 * and {@link StandardOpenOption#WRITE WRITE} options are present. In other
170 * words, it opens the file for writing, creating the file if it doesn't
171 * exist, or initially truncating an existing {@link #isRegularFile
172 * regular-file} to a size of {@code 0} if it exists.
173 *
174 * <p> <b>Usage Examples:</b>
175 * <pre>
176 * Path path = ...
177 *
178 * // truncate and overwrite an existing file, or create the file if
179 * // it doesn't initially exist
180 * OutputStream out = Files.newOutputStream(path);
181 *
182 * // append to an existing file, fail if the file does not exist
183 * out = Files.newOutputStream(path, APPEND);
184 *
185 * // append to an existing file, create file if it doesn't initially exist
186 * out = Files.newOutputStream(path, CREATE, APPEND);
187 *
188 * // always create new file, failing if it already exists
189 * out = Files.newOutputStream(path, CREATE_NEW);
190 * </pre>
191 *
192 * @param path
193 * the path to the file to open or create
194 * @param options
195 * options specifying how the file is opened
196 *
197 * @return a new output stream
198 *
199 * @throws IllegalArgumentException
200 * if {@code options} contains an invalid combination of options
201 * @throws UnsupportedOperationException
202 * if an unsupported option is specified
203 * @throws IOException
204 * if an I/O error occurs
205 * @throws SecurityException
206 * In the case of the default provider, and a security manager is
207 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
208 * method is invoked to check write access to the file. The {@link
209 * SecurityManager#checkDelete(String) checkDelete} method is
210 * invoked to check delete access if the file is opened with the
211 * {@code DELETE_ON_CLOSE} option.
212 */
213 public static OutputStream newOutputStream(Path path, OpenOption... options)
214 throws IOException
215 {
216 return provider(path).newOutputStream(path, options);
217 }
218
219 /**
220 * Opens or creates a file, returning a seekable byte channel to access the
221 * file.
222 *
223 * <p> The {@code options} parameter determines how the file is opened.
224 * The {@link StandardOpenOption#READ READ} and {@link
225 * StandardOpenOption#WRITE WRITE} options determine if the file should be
226 * opened for reading and/or writing. If neither option (or the {@link
227 * StandardOpenOption#APPEND APPEND} option) is present then the file is
228 * opened for reading. By default reading or writing commence at the
229 * beginning of the file.
230 *
231 * <p> In the addition to {@code READ} and {@code WRITE}, the following
232 * options may be present:
233 *
234 * <table border=1 cellpadding=5 summary="Options">
235 * <tr> <th>Option</th> <th>Description</th> </tr>
236 * <tr>
237 * <td> {@link StandardOpenOption#APPEND APPEND} </td>
238 * <td> If this option is present then the file is opened for writing and
239 * each invocation of the channel's {@code write} method first advances
240 * the position to the end of the file and then writes the requested
241 * data. Whether the advancement of the position and the writing of the
242 * data are done in a single atomic operation is system-dependent and
243 * therefore unspecified. This option may not be used in conjunction
244 * with the {@code READ} or {@code TRUNCATE_EXISTING} options. </td>
245 * </tr>
246 * <tr>
247 * <td> {@link StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING} </td>
248 * <td> If this option is present then the existing file is truncated to
249 * a size of 0 bytes. This option is ignored when the file is opened only
250 * for reading. </td>
251 * </tr>
252 * <tr>
253 * <td> {@link StandardOpenOption#CREATE_NEW CREATE_NEW} </td>
254 * <td> If this option is present then a new file is created, failing if
255 * the file already exists or is a symbolic link. When creating a file the
256 * check for the existence of the file and the creation of the file if it
257 * does not exist is atomic with respect to other file system operations.
258 * This option is ignored when the file is opened only for reading. </td>
259 * </tr>
260 * <tr>
261 * <td > {@link StandardOpenOption#CREATE CREATE} </td>
262 * <td> If this option is present then an existing file is opened if it
263 * exists, otherwise a new file is created. This option is ignored if the
264 * {@code CREATE_NEW} option is also present or the file is opened only
265 * for reading. </td>
266 * </tr>
267 * <tr>
268 * <td > {@link StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE} </td>
269 * <td> When this option is present then the implementation makes a
270 * <em>best effort</em> attempt to delete the file when closed by the
271 * {@link SeekableByteChannel#close close} method. If the {@code close}
272 * method is not invoked then a <em>best effort</em> attempt is made to
273 * delete the file when the Java virtual machine terminates. </td>
274 * </tr>
275 * <tr>
276 * <td>{@link StandardOpenOption#SPARSE SPARSE} </td>
277 * <td> When creating a new file this option is a <em>hint</em> that the
278 * new file will be sparse. This option is ignored when not creating
279 * a new file. </td>
280 * </tr>
281 * <tr>
282 * <td> {@link StandardOpenOption#SYNC SYNC} </td>
283 * <td> Requires that every update to the file's content or metadata be
284 * written synchronously to the underlying storage device. (see <a
285 * href="package-summary.html#integrity"> Synchronized I/O file
286 * integrity</a>). </td>
287 * </tr>
288 * <tr>
289 * <td> {@link StandardOpenOption#DSYNC DSYNC} </td>
290 * <td> Requires that every update to the file's content be written
291 * synchronously to the underlying storage device. (see <a
292 * href="package-summary.html#integrity"> Synchronized I/O file
293 * integrity</a>). </td>
294 * </tr>
295 * </table>
296 *
297 * <p> An implementation may also support additional implementation specific
298 * options.
299 *
300 * <p> The {@code attrs} parameter is optional {@link FileAttribute
301 * file-attributes} to set atomically when a new file is created.
302 *
303 * <p> In the case of the default provider, the returned seekable byte channel
304 * is a {@link java.nio.channels.FileChannel}.
305 *
306 * <p> <b>Usage Examples:</b>
307 * <pre>
308 * Path path = ...
309 *
310 * // open file for reading
311 * ReadableByteChannel rbc = Files.newByteChannel(path, EnumSet.of(READ)));
312 *
313 * // open file for writing to the end of an existing file, creating
314 * // the file if it doesn't already exist
315 * WritableByteChannel wbc = Files.newByteChannel(path, EnumSet.of(CREATE,APPEND));
316 *
317 * // create file with initial permissions, opening it for both reading and writing
318 * {@code FileAttribute<Set<PosixFilePermission>> perms = ...}
319 * SeekableByteChannel sbc = Files.newByteChannel(path, EnumSet.of(CREATE_NEW,READ,WRITE), perms);
320 * </pre>
321 *
322 * @param path
323 * the path to the file to open or create
324 * @param options
325 * options specifying how the file is opened
326 * @param attrs
327 * an optional list of file attributes to set atomically when
328 * creating the file
329 *
330 * @return a new seekable byte channel
331 *
332 * @throws IllegalArgumentException
333 * if the set contains an invalid combination of options
334 * @throws UnsupportedOperationException
335 * if an unsupported open option is specified or the array contains
336 * attributes that cannot be set atomically when creating the file
337 * @throws FileAlreadyExistsException
338 * if a file of that name already exists and the {@link
339 * StandardOpenOption#CREATE_NEW CREATE_NEW} option is specified
340 * <i>(optional specific exception)</i>
341 * @throws IOException
342 * if an I/O error occurs
343 * @throws SecurityException
344 * In the case of the default provider, and a security manager is
345 * installed, the {@link SecurityManager#checkRead(String) checkRead}
346 * method is invoked to check read access to the path if the file is
347 * opened for reading. The {@link SecurityManager#checkWrite(String)
348 * checkWrite} method is invoked to check write access to the path
349 * if the file is opened for writing. The {@link
350 * SecurityManager#checkDelete(String) checkDelete} method is
351 * invoked to check delete access if the file is opened with the
352 * {@code DELETE_ON_CLOSE} option.
353 *
354 * @see java.nio.channels.FileChannel#open(Path,Set,FileAttribute[])
355 */
356 public static SeekableByteChannel newByteChannel(Path path,
357 Set<? extends OpenOption> options,
358 FileAttribute<?>... attrs)
359 throws IOException
360 {
361 return provider(path).newByteChannel(path, options, attrs);
362 }
363
364 /**
365 * Opens or creates a file, returning a seekable byte channel to access the
366 * file.
367 *
368 * <p> This method opens or creates a file in exactly the manner specified
369 * by the {@link #newByteChannel(Path,Set,FileAttribute[]) newByteChannel}
370 * method.
371 *
372 * @param path
373 * the path to the file to open or create
374 * @param options
375 * options specifying how the file is opened
376 *
377 * @return a new seekable byte channel
378 *
379 * @throws IllegalArgumentException
380 * if the set contains an invalid combination of options
381 * @throws UnsupportedOperationException
382 * if an unsupported open option is specified
383 * @throws FileAlreadyExistsException
384 * if a file of that name already exists and the {@link
385 * StandardOpenOption#CREATE_NEW CREATE_NEW} option is specified
386 * <i>(optional specific exception)</i>
387 * @throws IOException
388 * if an I/O error occurs
389 * @throws SecurityException
390 * In the case of the default provider, and a security manager is
391 * installed, the {@link SecurityManager#checkRead(String) checkRead}
392 * method is invoked to check read access to the path if the file is
393 * opened for reading. The {@link SecurityManager#checkWrite(String)
394 * checkWrite} method is invoked to check write access to the path
395 * if the file is opened for writing. The {@link
396 * SecurityManager#checkDelete(String) checkDelete} method is
397 * invoked to check delete access if the file is opened with the
398 * {@code DELETE_ON_CLOSE} option.
399 *
400 * @see java.nio.channels.FileChannel#open(Path,OpenOption[])
401 */
402 public static SeekableByteChannel newByteChannel(Path path, OpenOption... options)
403 throws IOException
404 {
405 Set<OpenOption> set = new HashSet<OpenOption>(options.length);
406 Collections.addAll(set, options);
407 return newByteChannel(path, set);
408 }
409
410 // -- Directories --
411
412 private static class AcceptAllFilter
413 implements DirectoryStream.Filter<Path>
414 {
415 private AcceptAllFilter() { }
416
417 @Override
418 public boolean accept(Path entry) { return true; }
419
420 static final AcceptAllFilter FILTER = new AcceptAllFilter();
421 }
422
423 /**
424 * Opens a directory, returning a {@link DirectoryStream} to iterate over
425 * all entries in the directory. The elements returned by the directory
426 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
427 * Path}, each one representing an entry in the directory. The {@code Path}
428 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
429 * name of the directory entry against {@code dir}.
430 *
431 * <p> When not using the try-with-resources construct, then directory
432 * stream's {@code close} method should be invoked after iteration is
433 * completed so as to free any resources held for the open directory.
434 *
435 * <p> When an implementation supports operations on entries in the
436 * directory that execute in a race-free manner then the returned directory
437 * stream is a {@link SecureDirectoryStream}.
438 *
439 * @param dir
440 * the path to the directory
441 *
442 * @return a new and open {@code DirectoryStream} object
443 *
444 * @throws NotDirectoryException
445 * if the file could not otherwise be opened because it is not
446 * a directory <i>(optional specific exception)</i>
447 * @throws IOException
448 * if an I/O error occurs
449 * @throws SecurityException
450 * In the case of the default provider, and a security manager is
451 * installed, the {@link SecurityManager#checkRead(String) checkRead}
452 * method is invoked to check read access to the directory.
453 */
454 public static DirectoryStream<Path> newDirectoryStream(Path dir)
455 throws IOException
456 {
457 return provider(dir).newDirectoryStream(dir, AcceptAllFilter.FILTER);
458 }
459
460 /**
461 * Opens a directory, returning a {@link DirectoryStream} to iterate over
462 * the entries in the directory. The elements returned by the directory
463 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
464 * Path}, each one representing an entry in the directory. The {@code Path}
465 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
466 * name of the directory entry against {@code dir}. The entries returned by
467 * the iterator are filtered by matching the {@code String} representation
468 * of their file names against the given <em>globbing</em> pattern.
469 *
470 * <p> For example, suppose we want to iterate over the files ending with
471 * ".java" in a directory:
472 * <pre>
473 * Path dir = ...
474 * try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, "*.java")) {
475 * :
476 * }
477 * </pre>
478 *
479 * <p> The globbing pattern is specified by the {@link
480 * FileSystem#getPathMatcher getPathMatcher} method.
481 *
482 * <p> When not using the try-with-resources construct, then directory
483 * stream's {@code close} method should be invoked after iteration is
484 * completed so as to free any resources held for the open directory.
485 *
486 * <p> When an implementation supports operations on entries in the
487 * directory that execute in a race-free manner then the returned directory
488 * stream is a {@link SecureDirectoryStream}.
489 *
490 * @param dir
491 * the path to the directory
492 * @param glob
493 * the glob pattern
494 *
495 * @return a new and open {@code DirectoryStream} object
496 *
497 * @throws java.util.regex.PatternSyntaxException
498 * if the pattern is invalid
499 * @throws NotDirectoryException
500 * if the file could not otherwise be opened because it is not
501 * a directory <i>(optional specific exception)</i>
502 * @throws IOException
503 * if an I/O error occurs
504 * @throws SecurityException
505 * In the case of the default provider, and a security manager is
506 * installed, the {@link SecurityManager#checkRead(String) checkRead}
507 * method is invoked to check read access to the directory.
508 */
509 public static DirectoryStream<Path> newDirectoryStream(Path dir, String glob)
510 throws IOException
511 {
512 // avoid creating a matcher if all entries are required.
513 if (glob.equals("*"))
514 return newDirectoryStream(dir);
515
516 // create a matcher and return a filter that uses it.
517 FileSystem fs = dir.getFileSystem();
518 final PathMatcher matcher = fs.getPathMatcher("glob:" + glob);
519 DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
520 @Override
521 public boolean accept(Path entry) {
522 return matcher.matches(entry.getFileName());
523 }
524 };
525 return fs.provider().newDirectoryStream(dir, filter);
526 }
527
528 /**
529 * Opens a directory, returning a {@link DirectoryStream} to iterate over
530 * the entries in the directory. The elements returned by the directory
531 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
532 * Path}, each one representing an entry in the directory. The {@code Path}
533 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
534 * name of the directory entry against {@code dir}. The entries returned by
535 * the iterator are filtered by the given {@link DirectoryStream.Filter
536 * filter}.
537 *
538 * <p> When not using the try-with-resources construct, then directory
539 * stream's {@code close} method should be invoked after iteration is
540 * completed so as to free any resources held for the open directory.
541 *
542 * <p> Where the filter terminates due to an uncaught error or runtime
543 * exception then it is propagated to the {@link Iterator#hasNext()
544 * hasNext} or {@link Iterator#next() next} method. Where an {@code
545 * IOException} is thrown, it results in the {@code hasNext} or {@code
546 * next} method throwing a {@link DirectoryIteratorException} with the
547 * {@code IOException} as the cause.
548 *
549 * <p> When an implementation supports operations on entries in the
550 * directory that execute in a race-free manner then the returned directory
551 * stream is a {@link SecureDirectoryStream}.
552 *
553 * <p> <b>Usage Example:</b>
554 * Suppose we want to iterate over the files in a directory that are
555 * larger than 8K.
556 * <pre>
557 * DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
558 * public boolean accept(Path file) throws IOException {
559 * return (Files.size(file) > 8192L);
560 * }
561 * };
562 * Path dir = ...
563 * try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, filter)) {
564 * :
565 * }
566 * </pre>
567 *
568 * @param dir
569 * the path to the directory
570 * @param filter
571 * the directory stream filter
572 *
573 * @return a new and open {@code DirectoryStream} object
574 *
575 * @throws NotDirectoryException
576 * if the file could not otherwise be opened because it is not
577 * a directory <i>(optional specific exception)</i>
578 * @throws IOException
579 * if an I/O error occurs
580 * @throws SecurityException
581 * In the case of the default provider, and a security manager is
582 * installed, the {@link SecurityManager#checkRead(String) checkRead}
583 * method is invoked to check read access to the directory.
584 */
585 public static DirectoryStream<Path> newDirectoryStream(Path dir,
586 DirectoryStream.Filter<? super Path> filter)
587 throws IOException
588 {
589 return provider(dir).newDirectoryStream(dir, filter);
590 }
591
592 // -- Creation and deletion --
593
594 /**
595 * Creates a new and empty file, failing if the file already exists. The
596 * check for the existence of the file and the creation of the new file if
597 * it does not exist are a single operation that is atomic with respect to
598 * all other filesystem activities that might affect the directory.
599 *
600 * <p> The {@code attrs} parameter is optional {@link FileAttribute
601 * file-attributes} to set atomically when creating the file. Each attribute
602 * is identified by its {@link FileAttribute#name name}. If more than one
603 * attribute of the same name is included in the array then all but the last
604 * occurrence is ignored.
605 *
606 * @param path
607 * the path to the file to create
608 * @param attrs
609 * an optional list of file attributes to set atomically when
610 * creating the file
611 *
612 * @return the file
613 *
614 * @throws UnsupportedOperationException
615 * if the array contains an attribute that cannot be set atomically
616 * when creating the file
617 * @throws FileAlreadyExistsException
618 * if a file of that name already exists
619 * <i>(optional specific exception)</i>
620 * @throws IOException
621 * if an I/O error occurs or the parent directory does not exist
622 * @throws SecurityException
623 * In the case of the default provider, and a security manager is
624 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
625 * method is invoked to check write access to the new file.
626 */
627 public static Path createFile(Path path, FileAttribute<?>... attrs)
628 throws IOException
629 {
630 EnumSet<StandardOpenOption> options =
631 EnumSet.<StandardOpenOption>of(StandardOpenOption.CREATE_NEW, StandardOpenOption.WRITE);
632 newByteChannel(path, options, attrs).close();
633 return path;
634 }
635
636 /**
637 * Creates a new directory. The check for the existence of the file and the
638 * creation of the directory if it does not exist are a single operation
639 * that is atomic with respect to all other filesystem activities that might
640 * affect the directory. The {@link #createDirectories createDirectories}
641 * method should be used where it is required to create all nonexistent
642 * parent directories first.
643 *
644 * <p> The {@code attrs} parameter is optional {@link FileAttribute
645 * file-attributes} to set atomically when creating the directory. Each
646 * attribute is identified by its {@link FileAttribute#name name}. If more
647 * than one attribute of the same name is included in the array then all but
648 * the last occurrence is ignored.
649 *
650 * @param dir
651 * the directory to create
652 * @param attrs
653 * an optional list of file attributes to set atomically when
654 * creating the directory
655 *
656 * @return the directory
657 *
658 * @throws UnsupportedOperationException
659 * if the array contains an attribute that cannot be set atomically
660 * when creating the directory
661 * @throws FileAlreadyExistsException
662 * if a directory could not otherwise be created because a file of
663 * that name already exists <i>(optional specific exception)</i>
664 * @throws IOException
665 * if an I/O error occurs or the parent directory does not exist
666 * @throws SecurityException
667 * In the case of the default provider, and a security manager is
668 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
669 * method is invoked to check write access to the new directory.
670 */
671 public static Path createDirectory(Path dir, FileAttribute<?>... attrs)
672 throws IOException
673 {
674 provider(dir).createDirectory(dir, attrs);
675 return dir;
676 }
677
678 /**
679 * Creates a directory by creating all nonexistent parent directories first.
680 * Unlike the {@link #createDirectory createDirectory} method, an exception
681 * is not thrown if the directory could not be created because it already
682 * exists.
683 *
684 * <p> The {@code attrs} parameter is optional {@link FileAttribute
685 * file-attributes} to set atomically when creating the nonexistent
686 * directories. Each file attribute is identified by its {@link
687 * FileAttribute#name name}. If more than one attribute of the same name is
688 * included in the array then all but the last occurrence is ignored.
689 *
690 * <p> If this method fails, then it may do so after creating some, but not
691 * all, of the parent directories.
692 *
693 * @param dir
694 * the directory to create
695 *
696 * @param attrs
697 * an optional list of file attributes to set atomically when
698 * creating the directory
699 *
700 * @return the directory
701 *
702 * @throws UnsupportedOperationException
703 * if the array contains an attribute that cannot be set atomically
704 * when creating the directory
705 * @throws FileAlreadyExistsException
706 * if {@code dir} exists but is not a directory <i>(optional specific
707 * exception)</i>
708 * @throws IOException
709 * if an I/O error occurs
710 * @throws SecurityException
711 * in the case of the default provider, and a security manager is
712 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
713 * method is invoked prior to attempting to create a directory and
714 * its {@link SecurityManager#checkRead(String) checkRead} is
715 * invoked for each parent directory that is checked. If {@code
716 * dir} is not an absolute path then its {@link Path#toAbsolutePath
717 * toAbsolutePath} may need to be invoked to get its absolute path.
718 * This may invoke the security manager's {@link
719 * SecurityManager#checkPropertyAccess(String) checkPropertyAccess}
720 * method to check access to the system property {@code user.dir}
721 */
722 public static Path createDirectories(Path dir, FileAttribute<?>... attrs)
723 throws IOException
724 {
725 // attempt to create the directory
726 try {
727 createAndCheckIsDirectory(dir, attrs);
728 return dir;
729 } catch (FileAlreadyExistsException x) {
730 // file exists and is not a directory
731 throw x;
732 } catch (IOException x) {
733 // parent may not exist or other reason
734 }
735 SecurityException se = null;
736 try {
737 dir = dir.toAbsolutePath();
738 } catch (SecurityException x) {
739 // don't have permission to get absolute path
740 se = x;
741 }
742 // find a decendent that exists
743 Path parent = dir.getParent();
744 while (parent != null) {
745 try {
746 provider(parent).checkAccess(parent);
747 break;
748 } catch (NoSuchFileException x) {
749 // does not exist
750 }
751 parent = parent.getParent();
752 }
753 if (parent == null) {
754 // unable to find existing parent
755 if (se == null) {
756 throw new FileSystemException(dir.toString(), null,
757 "Unable to determine if root directory exists");
758 } else {
759 throw se;
760 }
761 }
762
763 // create directories
764 Path child = parent;
765 for (Path name: parent.relativize(dir)) {
766 child = child.resolve(name);
767 createAndCheckIsDirectory(child, attrs);
768 }
769 return dir;
770 }
771
772 /**
773 * Used by createDirectories to attempt to create a directory. A no-op
774 * if the directory already exists.
775 */
776 private static void createAndCheckIsDirectory(Path dir,
777 FileAttribute<?>... attrs)
778 throws IOException
779 {
780 try {
781 createDirectory(dir, attrs);
782 } catch (FileAlreadyExistsException x) {
783 if (!isDirectory(dir, LinkOption.NOFOLLOW_LINKS))
784 throw x;
785 }
786 }
787
788 /**
789 * Creates a new empty file in the specified directory, using the given
790 * prefix and suffix strings to generate its name. The resulting
791 * {@code Path} is associated with the same {@code FileSystem} as the given
792 * directory.
793 *
794 * <p> The details as to how the name of the file is constructed is
795 * implementation dependent and therefore not specified. Where possible
796 * the {@code prefix} and {@code suffix} are used to construct candidate
797 * names in the same manner as the {@link
798 * java.io.File#createTempFile(String,String,File)} method.
799 *
800 * <p> As with the {@code File.createTempFile} methods, this method is only
801 * part of a temporary-file facility. Where used as a <em>work files</em>,
802 * the resulting file may be opened using the {@link
803 * StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE} option so that the
804 * file is deleted when the appropriate {@code close} method is invoked.
805 * Alternatively, a {@link Runtime#addShutdownHook shutdown-hook}, or the
806 * {@link java.io.File#deleteOnExit} mechanism may be used to delete the
807 * file automatically.
808 *
809 * <p> The {@code attrs} parameter is optional {@link FileAttribute
810 * file-attributes} to set atomically when creating the file. Each attribute
811 * is identified by its {@link FileAttribute#name name}. If more than one
812 * attribute of the same name is included in the array then all but the last
813 * occurrence is ignored. When no file attributes are specified, then the
814 * resulting file may have more restrictive access permissions to files
815 * created by the {@link java.io.File#createTempFile(String,String,File)}
816 * method.
817 *
818 * @param dir
819 * the path to directory in which to create the file
820 * @param prefix
821 * the prefix string to be used in generating the file's name;
822 * may be {@code null}
823 * @param suffix
824 * the suffix string to be used in generating the file's name;
825 * may be {@code null}, in which case "{@code .tmp}" is used
826 * @param attrs
827 * an optional list of file attributes to set atomically when
828 * creating the file
829 *
830 * @return the path to the newly created file that did not exist before
831 * this method was invoked
832 *
833 * @throws IllegalArgumentException
834 * if the prefix or suffix parameters cannot be used to generate
835 * a candidate file name
836 * @throws UnsupportedOperationException
837 * if the array contains an attribute that cannot be set atomically
838 * when creating the directory
839 * @throws IOException
840 * if an I/O error occurs or {@code dir} does not exist
841 * @throws SecurityException
842 * In the case of the default provider, and a security manager is
843 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
844 * method is invoked to check write access to the file.
845 */
846 public static Path createTempFile(Path dir,
847 String prefix,
848 String suffix,
849 FileAttribute<?>... attrs)
850 throws IOException
851 {
852 return TempFileHelper.createTempFile(Objects.requireNonNull(dir),
853 prefix, suffix, attrs);
854 }
855
856 /**
857 * Creates an empty file in the default temporary-file directory, using
858 * the given prefix and suffix to generate its name. The resulting {@code
859 * Path} is associated with the default {@code FileSystem}.
860 *
861 * <p> This method works in exactly the manner specified by the
862 * {@link #createTempFile(Path,String,String,FileAttribute[])} method for
863 * the case that the {@code dir} parameter is the temporary-file directory.
864 *
865 * @param prefix
866 * the prefix string to be used in generating the file's name;
867 * may be {@code null}
868 * @param suffix
869 * the suffix string to be used in generating the file's name;
870 * may be {@code null}, in which case "{@code .tmp}" is used
871 * @param attrs
872 * an optional list of file attributes to set atomically when
873 * creating the file
874 *
875 * @return the path to the newly created file that did not exist before
876 * this method was invoked
877 *
878 * @throws IllegalArgumentException
879 * if the prefix or suffix parameters cannot be used to generate
880 * a candidate file name
881 * @throws UnsupportedOperationException
882 * if the array contains an attribute that cannot be set atomically
883 * when creating the directory
884 * @throws IOException
885 * if an I/O error occurs or the temporary-file directory does not
886 * exist
887 * @throws SecurityException
888 * In the case of the default provider, and a security manager is
889 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
890 * method is invoked to check write access to the file.
891 */
892 public static Path createTempFile(String prefix,
893 String suffix,
894 FileAttribute<?>... attrs)
895 throws IOException
896 {
897 return TempFileHelper.createTempFile(null, prefix, suffix, attrs);
898 }
899
900 /**
901 * Creates a new directory in the specified directory, using the given
902 * prefix to generate its name. The resulting {@code Path} is associated
903 * with the same {@code FileSystem} as the given directory.
904 *
905 * <p> The details as to how the name of the directory is constructed is
906 * implementation dependent and therefore not specified. Where possible
907 * the {@code prefix} is used to construct candidate names.
908 *
909 * <p> As with the {@code createTempFile} methods, this method is only
910 * part of a temporary-file facility. A {@link Runtime#addShutdownHook
911 * shutdown-hook}, or the {@link java.io.File#deleteOnExit} mechanism may be
912 * used to delete the directory automatically.
913 *
914 * <p> The {@code attrs} parameter is optional {@link FileAttribute
915 * file-attributes} to set atomically when creating the directory. Each
916 * attribute is identified by its {@link FileAttribute#name name}. If more
917 * than one attribute of the same name is included in the array then all but
918 * the last occurrence is ignored.
919 *
920 * @param dir
921 * the path to directory in which to create the directory
922 * @param prefix
923 * the prefix string to be used in generating the directory's name;
924 * may be {@code null}
925 * @param attrs
926 * an optional list of file attributes to set atomically when
927 * creating the directory
928 *
929 * @return the path to the newly created directory that did not exist before
930 * this method was invoked
931 *
932 * @throws IllegalArgumentException
933 * if the prefix cannot be used to generate a candidate directory name
934 * @throws UnsupportedOperationException
935 * if the array contains an attribute that cannot be set atomically
936 * when creating the directory
937 * @throws IOException
938 * if an I/O error occurs or {@code dir} does not exist
939 * @throws SecurityException
940 * In the case of the default provider, and a security manager is
941 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
942 * method is invoked to check write access when creating the
943 * directory.
944 */
945 public static Path createTempDirectory(Path dir,
946 String prefix,
947 FileAttribute<?>... attrs)
948 throws IOException
949 {
950 return TempFileHelper.createTempDirectory(Objects.requireNonNull(dir),
951 prefix, attrs);
952 }
953
954 /**
955 * Creates a new directory in the default temporary-file directory, using
956 * the given prefix to generate its name. The resulting {@code Path} is
957 * associated with the default {@code FileSystem}.
958 *
959 * <p> This method works in exactly the manner specified by {@link
960 * #createTempDirectory(Path,String,FileAttribute[])} method for the case
961 * that the {@code dir} parameter is the temporary-file directory.
962 *
963 * @param prefix
964 * the prefix string to be used in generating the directory's name;
965 * may be {@code null}
966 * @param attrs
967 * an optional list of file attributes to set atomically when
968 * creating the directory
969 *
970 * @return the path to the newly created directory that did not exist before
971 * this method was invoked
972 *
973 * @throws IllegalArgumentException
974 * if the prefix cannot be used to generate a candidate directory name
975 * @throws UnsupportedOperationException
976 * if the array contains an attribute that cannot be set atomically
977 * when creating the directory
978 * @throws IOException
979 * if an I/O error occurs or the temporary-file directory does not
980 * exist
981 * @throws SecurityException
982 * In the case of the default provider, and a security manager is
983 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
984 * method is invoked to check write access when creating the
985 * directory.
986 */
987 public static Path createTempDirectory(String prefix,
988 FileAttribute<?>... attrs)
989 throws IOException
990 {
991 return TempFileHelper.createTempDirectory(null, prefix, attrs);
992 }
993
994 /**
995 * Creates a symbolic link to a target <i>(optional operation)</i>.
996 *
997 * <p> The {@code target} parameter is the target of the link. It may be an
998 * {@link Path#isAbsolute absolute} or relative path and may not exist. When
999 * the target is a relative path then file system operations on the resulting
1000 * link are relative to the path of the link.
1001 *
1002 * <p> The {@code attrs} parameter is optional {@link FileAttribute
1003 * attributes} to set atomically when creating the link. Each attribute is
1004 * identified by its {@link FileAttribute#name name}. If more than one attribute
1005 * of the same name is included in the array then all but the last occurrence
1006 * is ignored.
1007 *
1008 * <p> Where symbolic links are supported, but the underlying {@link FileStore}
1009 * does not support symbolic links, then this may fail with an {@link
1010 * IOException}. Additionally, some operating systems may require that the
1011 * Java virtual machine be started with implementation specific privileges to
1012 * create symbolic links, in which case this method may throw {@code IOException}.
1013 *
1014 * @param link
1015 * the path of the symbolic link to create
1016 * @param target
1017 * the target of the symbolic link
1018 * @param attrs
1019 * the array of attributes to set atomically when creating the
1020 * symbolic link
1021 *
1022 * @return the path to the symbolic link
1023 *
1024 * @throws UnsupportedOperationException
1025 * if the implementation does not support symbolic links or the
1026 * array contains an attribute that cannot be set atomically when
1027 * creating the symbolic link
1028 * @throws FileAlreadyExistsException
1029 * if a file with the name already exists <i>(optional specific
1030 * exception)</i>
1031 * @throws IOException
1032 * if an I/O error occurs
1033 * @throws SecurityException
1034 * In the case of the default provider, and a security manager
1035 * is installed, it denies {@link LinkPermission}<tt>("symbolic")</tt>
1036 * or its {@link SecurityManager#checkWrite(String) checkWrite}
1037 * method denies write access to the path of the symbolic link.
1038 */
1039 public static Path createSymbolicLink(Path link, Path target,
1040 FileAttribute<?>... attrs)
1041 throws IOException
1042 {
1043 provider(link).createSymbolicLink(link, target, attrs);
1044 return link;
1045 }
1046
1047 /**
1048 * Creates a new link (directory entry) for an existing file <i>(optional
1049 * operation)</i>.
1050 *
1051 * <p> The {@code link} parameter locates the directory entry to create.
1052 * The {@code existing} parameter is the path to an existing file. This
1053 * method creates a new directory entry for the file so that it can be
1054 * accessed using {@code link} as the path. On some file systems this is
1055 * known as creating a "hard link". Whether the file attributes are
1056 * maintained for the file or for each directory entry is file system
1057 * specific and therefore not specified. Typically, a file system requires
1058 * that all links (directory entries) for a file be on the same file system.
1059 * Furthermore, on some platforms, the Java virtual machine may require to
1060 * be started with implementation specific privileges to create hard links
1061 * or to create links to directories.
1062 *
1063 * @param link
1064 * the link (directory entry) to create
1065 * @param existing
1066 * a path to an existing file
1067 *
1068 * @return the path to the link (directory entry)
1069 *
1070 * @throws UnsupportedOperationException
1071 * if the implementation does not support adding an existing file
1072 * to a directory
1073 * @throws FileAlreadyExistsException
1074 * if the entry could not otherwise be created because a file of
1075 * that name already exists <i>(optional specific exception)</i>
1076 * @throws IOException
1077 * if an I/O error occurs
1078 * @throws SecurityException
1079 * In the case of the default provider, and a security manager
1080 * is installed, it denies {@link LinkPermission}<tt>("hard")</tt>
1081 * or its {@link SecurityManager#checkWrite(String) checkWrite}
1082 * method denies write access to either the link or the
1083 * existing file.
1084 */
1085 public static Path createLink(Path link, Path existing) throws IOException {
1086 provider(link).createLink(link, existing);
1087 return link;
1088 }
1089
1090 /**
1091 * Deletes a file.
1092 *
1093 * <p> An implementation may require to examine the file to determine if the
1094 * file is a directory. Consequently this method may not be atomic with respect
1095 * to other file system operations. If the file is a symbolic link then the
1096 * symbolic link itself, not the final target of the link, is deleted.
1097 *
1098 * <p> If the file is a directory then the directory must be empty. In some
1099 * implementations a directory has entries for special files or links that
1100 * are created when the directory is created. In such implementations a
1101 * directory is considered empty when only the special entries exist.
1102 * This method can be used with the {@link #walkFileTree walkFileTree}
1103 * method to delete a directory and all entries in the directory, or an
1104 * entire <i>file-tree</i> where required.
1105 *
1106 * <p> On some operating systems it may not be possible to remove a file when
1107 * it is open and in use by this Java virtual machine or other programs.
1108 *
1109 * @param path
1110 * the path to the file to delete
1111 *
1112 * @throws NoSuchFileException
1113 * if the file does not exist <i>(optional specific exception)</i>
1114 * @throws DirectoryNotEmptyException
1115 * if the file is a directory and could not otherwise be deleted
1116 * because the directory is not empty <i>(optional specific
1117 * exception)</i>
1118 * @throws IOException
1119 * if an I/O error occurs
1120 * @throws SecurityException
1121 * In the case of the default provider, and a security manager is
1122 * installed, the {@link SecurityManager#checkDelete(String)} method
1123 * is invoked to check delete access to the file
1124 */
1125 public static void delete(Path path) throws IOException {
1126 provider(path).delete(path);
1127 }
1128
1129 /**
1130 * Deletes a file if it exists.
1131 *
1132 * <p> As with the {@link #delete(Path) delete(Path)} method, an
1133 * implementation may need to examine the file to determine if the file is a
1134 * directory. Consequently this method may not be atomic with respect to
1135 * other file system operations. If the file is a symbolic link, then the
1136 * symbolic link itself, not the final target of the link, is deleted.
1137 *
1138 * <p> If the file is a directory then the directory must be empty. In some
1139 * implementations a directory has entries for special files or links that
1140 * are created when the directory is created. In such implementations a
1141 * directory is considered empty when only the special entries exist.
1142 *
1143 * <p> On some operating systems it may not be possible to remove a file when
1144 * it is open and in use by this Java virtual machine or other programs.
1145 *
1146 * @param path
1147 * the path to the file to delete
1148 *
1149 * @return {@code true} if the file was deleted by this method; {@code
1150 * false} if the file could not be deleted because it did not
1151 * exist
1152 *
1153 * @throws DirectoryNotEmptyException
1154 * if the file is a directory and could not otherwise be deleted
1155 * because the directory is not empty <i>(optional specific
1156 * exception)</i>
1157 * @throws IOException
1158 * if an I/O error occurs
1159 * @throws SecurityException
1160 * In the case of the default provider, and a security manager is
1161 * installed, the {@link SecurityManager#checkDelete(String)} method
1162 * is invoked to check delete access to the file.
1163 */
1164 public static boolean deleteIfExists(Path path) throws IOException {
1165 return provider(path).deleteIfExists(path);
1166 }
1167
1168 // -- Copying and moving files --
1169
1170 /**
1171 * Copy a file to a target file.
1172 *
1173 * <p> This method copies a file to the target file with the {@code
1174 * options} parameter specifying how the copy is performed. By default, the
1175 * copy fails if the target file already exists or is a symbolic link,
1176 * except if the source and target are the {@link #isSameFile same} file, in
1177 * which case the method completes without copying the file. File attributes
1178 * are not required to be copied to the target file. If symbolic links are
1179 * supported, and the file is a symbolic link, then the final target of the
1180 * link is copied. If the file is a directory then it creates an empty
1181 * directory in the target location (entries in the directory are not
1182 * copied). This method can be used with the {@link #walkFileTree
1183 * walkFileTree} method to copy a directory and all entries in the directory,
1184 * or an entire <i>file-tree</i> where required.
1185 *
1186 * <p> The {@code options} parameter may include any of the following:
1187 *
1188 * <table border=1 cellpadding=5 summary="">
1189 * <tr> <th>Option</th> <th>Description</th> </tr>
1190 * <tr>
1191 * <td> {@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING} </td>
1192 * <td> If the target file exists, then the target file is replaced if it
1193 * is not a non-empty directory. If the target file exists and is a
1194 * symbolic link, then the symbolic link itself, not the target of
1195 * the link, is replaced. </td>
1196 * </tr>
1197 * <tr>
1198 * <td> {@link StandardCopyOption#COPY_ATTRIBUTES COPY_ATTRIBUTES} </td>
1199 * <td> Attempts to copy the file attributes associated with this file to
1200 * the target file. The exact file attributes that are copied is platform
1201 * and file system dependent and therefore unspecified. Minimally, the
1202 * {@link BasicFileAttributes#lastModifiedTime last-modified-time} is
1203 * copied to the target file if supported by both the source and target
1204 * file stores. Copying of file timestamps may result in precision
1205 * loss. </td>
1206 * </tr>
1207 * <tr>
1208 * <td> {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} </td>
1209 * <td> Symbolic links are not followed. If the file is a symbolic link,
1210 * then the symbolic link itself, not the target of the link, is copied.
1211 * It is implementation specific if file attributes can be copied to the
1212 * new link. In other words, the {@code COPY_ATTRIBUTES} option may be
1213 * ignored when copying a symbolic link. </td>
1214 * </tr>
1215 * </table>
1216 *
1217 * <p> An implementation of this interface may support additional
1218 * implementation specific options.
1219 *
1220 * <p> Copying a file is not an atomic operation. If an {@link IOException}
1221 * is thrown, then it is possible that the target file is incomplete or some
1222 * of its file attributes have not been copied from the source file. When
1223 * the {@code REPLACE_EXISTING} option is specified and the target file
1224 * exists, then the target file is replaced. The check for the existence of
1225 * the file and the creation of the new file may not be atomic with respect
1226 * to other file system activities.
1227 *
1228 * <p> <b>Usage Example:</b>
1229 * Suppose we want to copy a file into a directory, giving it the same file
1230 * name as the source file:
1231 * <pre>
1232 * Path source = ...
1233 * Path newdir = ...
1234 * Files.copy(source, newdir.resolve(source.getFileName());
1235 * </pre>
1236 *
1237 * @param source
1238 * the path to the file to copy
1239 * @param target
1240 * the path to the target file (may be associated with a different
1241 * provider to the source path)
1242 * @param options
1243 * options specifying how the copy should be done
1244 *
1245 * @return the path to the target file
1246 *
1247 * @throws UnsupportedOperationException
1248 * if the array contains a copy option that is not supported
1249 * @throws FileAlreadyExistsException
1250 * if the target file exists but cannot be replaced because the
1251 * {@code REPLACE_EXISTING} option is not specified <i>(optional
1252 * specific exception)</i>
1253 * @throws DirectoryNotEmptyException
1254 * the {@code REPLACE_EXISTING} option is specified but the file
1255 * cannot be replaced because it is a non-empty directory
1256 * <i>(optional specific exception)</i>
1257 * @throws IOException
1258 * if an I/O error occurs
1259 * @throws SecurityException
1260 * In the case of the default provider, and a security manager is
1261 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1262 * method is invoked to check read access to the source file, the
1263 * {@link SecurityManager#checkWrite(String) checkWrite} is invoked
1264 * to check write access to the target file. If a symbolic link is
1265 * copied the security manager is invoked to check {@link
1266 * LinkPermission}{@code ("symbolic")}.
1267 */
1268 public static Path copy(Path source, Path target, CopyOption... options)
1269 throws IOException
1270 {
1271 FileSystemProvider provider = provider(source);
1272 if (provider(target) == provider) {
1273 // same provider
1274 provider.copy(source, target, options);
1275 } else {
1276 // different providers
1277 CopyMoveHelper.copyToForeignTarget(source, target, options);
1278 }
1279 return target;
1280 }
1281
1282 /**
1283 * Move or rename a file to a target file.
1284 *
1285 * <p> By default, this method attempts to move the file to the target
1286 * file, failing if the target file exists except if the source and
1287 * target are the {@link #isSameFile same} file, in which case this method
1288 * has no effect. If the file is a symbolic link then the symbolic link
1289 * itself, not the target of the link, is moved. This method may be
1290 * invoked to move an empty directory. In some implementations a directory
1291 * has entries for special files or links that are created when the
1292 * directory is created. In such implementations a directory is considered
1293 * empty when only the special entries exist. When invoked to move a
1294 * directory that is not empty then the directory is moved if it does not
1295 * require moving the entries in the directory. For example, renaming a
1296 * directory on the same {@link FileStore} will usually not require moving
1297 * the entries in the directory. When moving a directory requires that its
1298 * entries be moved then this method fails (by throwing an {@code
1299 * IOException}). To move a <i>file tree</i> may involve copying rather
1300 * than moving directories and this can be done using the {@link
1301 * #copy copy} method in conjunction with the {@link
1302 * #walkFileTree Files.walkFileTree} utility method.
1303 *
1304 * <p> The {@code options} parameter may include any of the following:
1305 *
1306 * <table border=1 cellpadding=5 summary="">
1307 * <tr> <th>Option</th> <th>Description</th> </tr>
1308 * <tr>
1309 * <td> {@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING} </td>
1310 * <td> If the target file exists, then the target file is replaced if it
1311 * is not a non-empty directory. If the target file exists and is a
1312 * symbolic link, then the symbolic link itself, not the target of
1313 * the link, is replaced. </td>
1314 * </tr>
1315 * <tr>
1316 * <td> {@link StandardCopyOption#ATOMIC_MOVE ATOMIC_MOVE} </td>
1317 * <td> The move is performed as an atomic file system operation and all
1318 * other options are ignored. If the target file exists then it is
1319 * implementation specific if the existing file is replaced or this method
1320 * fails by throwing an {@link IOException}. If the move cannot be
1321 * performed as an atomic file system operation then {@link
1322 * AtomicMoveNotSupportedException} is thrown. This can arise, for
1323 * example, when the target location is on a different {@code FileStore}
1324 * and would require that the file be copied, or target location is
1325 * associated with a different provider to this object. </td>
1326 * </table>
1327 *
1328 * <p> An implementation of this interface may support additional
1329 * implementation specific options.
1330 *
1331 * <p> Moving a file will copy the {@link
1332 * BasicFileAttributes#lastModifiedTime last-modified-time} to the target
1333 * file if supported by both source and target file stores. Copying of file
1334 * timestamps may result in precision loss. An implementation may also
1335 * attempt to copy other file attributes but is not required to fail if the
1336 * file attributes cannot be copied. When the move is performed as
1337 * a non-atomic operation, and an {@code IOException} is thrown, then the
1338 * state of the files is not defined. The original file and the target file
1339 * may both exist, the target file may be incomplete or some of its file
1340 * attributes may not been copied from the original file.
1341 *
1342 * <p> <b>Usage Examples:</b>
1343 * Suppose we want to rename a file to "newname", keeping the file in the
1344 * same directory:
1345 * <pre>
1346 * Path source = ...
1347 * Files.move(source, source.resolveSibling("newname"));
1348 * </pre>
1349 * Alternatively, suppose we want to move a file to new directory, keeping
1350 * the same file name, and replacing any existing file of that name in the
1351 * directory:
1352 * <pre>
1353 * Path source = ...
1354 * Path newdir = ...
1355 * Files.move(source, newdir.resolve(source.getFileName()), REPLACE_EXISTING);
1356 * </pre>
1357 *
1358 * @param source
1359 * the path to the file to move
1360 * @param target
1361 * the path to the target file (may be associated with a different
1362 * provider to the source path)
1363 * @param options
1364 * options specifying how the move should be done
1365 *
1366 * @return the path to the target file
1367 *
1368 * @throws UnsupportedOperationException
1369 * if the array contains a copy option that is not supported
1370 * @throws FileAlreadyExistsException
1371 * if the target file exists but cannot be replaced because the
1372 * {@code REPLACE_EXISTING} option is not specified <i>(optional
1373 * specific exception)</i>
1374 * @throws DirectoryNotEmptyException
1375 * the {@code REPLACE_EXISTING} option is specified but the file
1376 * cannot be replaced because it is a non-empty directory
1377 * <i>(optional specific exception)</i>
1378 * @throws AtomicMoveNotSupportedException
1379 * if the options array contains the {@code ATOMIC_MOVE} option but
1380 * the file cannot be moved as an atomic file system operation.
1381 * @throws IOException
1382 * if an I/O error occurs
1383 * @throws SecurityException
1384 * In the case of the default provider, and a security manager is
1385 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
1386 * method is invoked to check write access to both the source and
1387 * target file.
1388 */
1389 public static Path move(Path source, Path target, CopyOption... options)
1390 throws IOException
1391 {
1392 FileSystemProvider provider = provider(source);
1393 if (provider(target) == provider) {
1394 // same provider
1395 provider.move(source, target, options);
1396 } else {
1397 // different providers
1398 CopyMoveHelper.moveToForeignTarget(source, target, options);
1399 }
1400 return target;
1401 }
1402
1403 // -- Miscellenous --
1404
1405 /**
1406 * Reads the target of a symbolic link <i>(optional operation)</i>.
1407 *
1408 * <p> If the file system supports <a href="package-summary.html#links">symbolic
1409 * links</a> then this method is used to read the target of the link, failing
1410 * if the file is not a symbolic link. The target of the link need not exist.
1411 * The returned {@code Path} object will be associated with the same file
1412 * system as {@code link}.
1413 *
1414 * @param link
1415 * the path to the symbolic link
1416 *
1417 * @return a {@code Path} object representing the target of the link
1418 *
1419 * @throws UnsupportedOperationException
1420 * if the implementation does not support symbolic links
1421 * @throws NotLinkException
1422 * if the target could otherwise not be read because the file
1423 * is not a symbolic link <i>(optional specific exception)</i>
1424 * @throws IOException
1425 * if an I/O error occurs
1426 * @throws SecurityException
1427 * In the case of the default provider, and a security manager
1428 * is installed, it checks that {@code FilePermission} has been
1429 * granted with the "{@code readlink}" action to read the link.
1430 */
1431 public static Path readSymbolicLink(Path link) throws IOException {
1432 return provider(link).readSymbolicLink(link);
1433 }
1434
1435 /**
1436 * Returns the {@link FileStore} representing the file store where a file
1437 * is located.
1438 *
1439 * <p> Once a reference to the {@code FileStore} is obtained it is
1440 * implementation specific if operations on the returned {@code FileStore},
1441 * or {@link FileStoreAttributeView} objects obtained from it, continue
1442 * to depend on the existence of the file. In particular the behavior is not
1443 * defined for the case that the file is deleted or moved to a different
1444 * file store.
1445 *
1446 * @param path
1447 * the path to the file
1448 *
1449 * @return the file store where the file is stored
1450 *
1451 * @throws IOException
1452 * if an I/O error occurs
1453 * @throws SecurityException
1454 * In the case of the default provider, and a security manager is
1455 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1456 * method is invoked to check read access to the file, and in
1457 * addition it checks {@link RuntimePermission}<tt>
1458 * ("getFileStoreAttributes")</tt>
1459 */
1460 public static FileStore getFileStore(Path path) throws IOException {
1461 return provider(path).getFileStore(path);
1462 }
1463
1464 /**
1465 * Tests if two paths locate the same file.
1466 *
1467 * <p> If both {@code Path} objects are {@link Path#equals(Object) equal}
1468 * then this method returns {@code true} without checking if the file exists.
1469 * If the two {@code Path} objects are associated with different providers
1470 * then this method returns {@code false}. Otherwise, this method checks if
1471 * both {@code Path} objects locate the same file, and depending on the
1472 * implementation, may require to open or access both files.
1473 *
1474 * <p> If the file system and files remain static, then this method implements
1475 * an equivalence relation for non-null {@code Paths}.
1476 * <ul>
1477 * <li>It is <i>reflexive</i>: for {@code Path} {@code f},
1478 * {@code isSameFile(f,f)} should return {@code true}.
1479 * <li>It is <i>symmetric</i>: for two {@code Paths} {@code f} and {@code g},
1480 * {@code isSameFile(f,g)} will equal {@code isSameFile(g,f)}.
1481 * <li>It is <i>transitive</i>: for three {@code Paths}
1482 * {@code f}, {@code g}, and {@code h}, if {@code isSameFile(f,g)} returns
1483 * {@code true} and {@code isSameFile(g,h)} returns {@code true}, then
1484 * {@code isSameFile(f,h)} will return return {@code true}.
1485 * </ul>
1486 *
1487 * @param path
1488 * one path to the file
1489 * @param path2
1490 * the other path
1491 *
1492 * @return {@code true} if, and only if, the two paths locate the same file
1493 *
1494 * @throws IOException
1495 * if an I/O error occurs
1496 * @throws SecurityException
1497 * In the case of the default provider, and a security manager is
1498 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1499 * method is invoked to check read access to both files.
1500 *
1501 * @see java.nio.file.attribute.BasicFileAttributes#fileKey
1502 */
1503 public static boolean isSameFile(Path path, Path path2) throws IOException {
1504 return provider(path).isSameFile(path, path2);
1505 }
1506
1507 /**
1508 * Tells whether or not a file is considered <em>hidden</em>. The exact
1509 * definition of hidden is platform or provider dependent. On UNIX for
1510 * example a file is considered to be hidden if its name begins with a
1511 * period character ('.'). On Windows a file is considered hidden if it
1512 * isn't a directory and the DOS {@link DosFileAttributes#isHidden hidden}
1513 * attribute is set.
1514 *
1515 * <p> Depending on the implementation this method may require to access
1516 * the file system to determine if the file is considered hidden.
1517 *
1518 * @param path
1519 * the path to the file to test
1520 *
1521 * @return {@code true} if the file is considered hidden
1522 *
1523 * @throws IOException
1524 * if an I/O error occurs
1525 * @throws SecurityException
1526 * In the case of the default provider, and a security manager is
1527 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1528 * method is invoked to check read access to the file.
1529 */
1530 public static boolean isHidden(Path path) throws IOException {
1531 return provider(path).isHidden(path);
1532 }
1533
1534 // lazy loading of default and installed file type detectors
1535 private static class FileTypeDetectors{
1536 static final FileTypeDetector defaultFileTypeDetector =
1537 createDefaultFileTypeDetector();
1538 static final List<FileTypeDetector> installeDetectors =
1539 loadInstalledDetectors();
1540
1541 // creates the default file type detector
1542 private static FileTypeDetector createDefaultFileTypeDetector() {
1543 return AccessController
1544 .doPrivileged(new PrivilegedAction<FileTypeDetector>() {
1545 @Override public FileTypeDetector run() {
1546 return sun.nio.fs.DefaultFileTypeDetector.create();
1547 }});
1548 }
1549
1550 // loads all installed file type detectors
1551 private static List<FileTypeDetector> loadInstalledDetectors() {
1552 return AccessController
1553 .doPrivileged(new PrivilegedAction<List<FileTypeDetector>>() {
1554 @Override public List<FileTypeDetector> run() {
1555 List<FileTypeDetector> list = new ArrayList<>();
1556 ServiceLoader<FileTypeDetector> loader = ServiceLoader
1557 .load(FileTypeDetector.class, ClassLoader.getSystemClassLoader());
1558 for (FileTypeDetector detector: loader) {
1559 list.add(detector);
1560 }
1561 return list;
1562 }});
1563 }
1564 }
1565
1566 /**
1567 * Probes the content type of a file.
1568 *
1569 * <p> This method uses the installed {@link FileTypeDetector} implementations
1570 * to probe the given file to determine its content type. Each file type
1571 * detector's {@link FileTypeDetector#probeContentType probeContentType} is
1572 * invoked, in turn, to probe the file type. If the file is recognized then
1573 * the content type is returned. If the file is not recognized by any of the
1574 * installed file type detectors then a system-default file type detector is
1575 * invoked to guess the content type.
1576 *
1577 * <p> A given invocation of the Java virtual machine maintains a system-wide
1578 * list of file type detectors. Installed file type detectors are loaded
1579 * using the service-provider loading facility defined by the {@link ServiceLoader}
1580 * class. Installed file type detectors are loaded using the system class
1581 * loader. If the system class loader cannot be found then the extension class
1582 * loader is used; If the extension class loader cannot be found then the
1583 * bootstrap class loader is used. File type detectors are typically installed
1584 * by placing them in a JAR file on the application class path or in the
1585 * extension directory, the JAR file contains a provider-configuration file
1586 * named {@code java.nio.file.spi.FileTypeDetector} in the resource directory
1587 * {@code META-INF/services}, and the file lists one or more fully-qualified
1588 * names of concrete subclass of {@code FileTypeDetector } that have a zero
1589 * argument constructor. If the process of locating or instantiating the
1590 * installed file type detectors fails then an unspecified error is thrown.
1591 * The ordering that installed providers are located is implementation
1592 * specific.
1593 *
1594 * <p> The return value of this method is the string form of the value of a
1595 * Multipurpose Internet Mail Extension (MIME) content type as
1596 * defined by <a href="http://www.ietf.org/rfc/rfc2045.txt"><i>RFC 2045:
1597 * Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet
1598 * Message Bodies</i></a>. The string is guaranteed to be parsable according
1599 * to the grammar in the RFC.
1600 *
1601 * @param path
1602 * the path to the file to probe
1603 *
1604 * @return The content type of the file, or {@code null} if the content
1605 * type cannot be determined
1606 *
1607 * @throws IOException
1608 * if an I/O error occurs
1609 * @throws SecurityException
1610 * If a security manager is installed and it denies an unspecified
1611 * permission required by a file type detector implementation.
1612 */
1613 public static String probeContentType(Path path)
1614 throws IOException
1615 {
1616 // try installed file type detectors
1617 for (FileTypeDetector detector: FileTypeDetectors.installeDetectors) {
1618 String result = detector.probeContentType(path);
1619 if (result != null)
1620 return result;
1621 }
1622
1623 // fallback to default
1624 return FileTypeDetectors.defaultFileTypeDetector.probeContentType(path);
1625 }
1626
1627 // -- File Attributes --
1628
1629 /**
1630 * Returns a file attribute view of a given type.
1631 *
1632 * <p> A file attribute view provides a read-only or updatable view of a
1633 * set of file attributes. This method is intended to be used where the file
1634 * attribute view defines type-safe methods to read or update the file
1635 * attributes. The {@code type} parameter is the type of the attribute view
1636 * required and the method returns an instance of that type if supported.
1637 * The {@link BasicFileAttributeView} type supports access to the basic
1638 * attributes of a file. Invoking this method to select a file attribute
1639 * view of that type will always return an instance of that class.
1640 *
1641 * <p> The {@code options} array may be used to indicate how symbolic links
1642 * are handled by the resulting file attribute view for the case that the
1643 * file is a symbolic link. By default, symbolic links are followed. If the
1644 * option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is present then
1645 * symbolic links are not followed. This option is ignored by implementations
1646 * that do not support symbolic links.
1647 *
1648 * <p> <b>Usage Example:</b>
1649 * Suppose we want read or set a file's ACL, if supported:
1650 * <pre>
1651 * Path path = ...
1652 * AclFileAttributeView view = Files.getFileAttributeView(path, AclFileAttributeView.class);
1653 * if (view != null) {
1654 * List<AclEntry> acl = view.getAcl();
1655 * :
1656 * }
1657 * </pre>
1658 *
1659 * @param <V>
1660 * The {@code FileAttributeView} type
1661 * @param path
1662 * the path to the file
1663 * @param type
1664 * the {@code Class} object corresponding to the file attribute view
1665 * @param options
1666 * options indicating how symbolic links are handled
1667 *
1668 * @return a file attribute view of the specified type, or {@code null} if
1669 * the attribute view type is not available
1670 */
1671 public static <V extends FileAttributeView> V getFileAttributeView(Path path,
1672 Class<V> type,
1673 LinkOption... options)
1674 {
1675 return provider(path).getFileAttributeView(path, type, options);
1676 }
1677
1678 /**
1679 * Reads a file's attributes as a bulk operation.
1680 *
1681 * <p> The {@code type} parameter is the type of the attributes required
1682 * and this method returns an instance of that type if supported. All
1683 * implementations support a basic set of file attributes and so invoking
1684 * this method with a {@code type} parameter of {@code
1685 * BasicFileAttributes.class} will not throw {@code
1686 * UnsupportedOperationException}.
1687 *
1688 * <p> The {@code options} array may be used to indicate how symbolic links
1689 * are handled for the case that the file is a symbolic link. By default,
1690 * symbolic links are followed and the file attribute of the final target
1691 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1692 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1693 *
1694 * <p> It is implementation specific if all file attributes are read as an
1695 * atomic operation with respect to other file system operations.
1696 *
1697 * <p> <b>Usage Example:</b>
1698 * Suppose we want to read a file's attributes in bulk:
1699 * <pre>
1700 * Path path = ...
1701 * BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class);
1702 * </pre>
1703 * Alternatively, suppose we want to read file's POSIX attributes without
1704 * following symbolic links:
1705 * <pre>
1706 * PosixFileAttributes attrs = Files.readAttributes(path, PosixFileAttributes.class, NOFOLLOW_LINKS);
1707 * </pre>
1708 *
1709 * @param <A>
1710 * The {@code BasicFileAttributes} type
1711 * @param path
1712 * the path to the file
1713 * @param type
1714 * the {@code Class} of the file attributes required
1715 * to read
1716 * @param options
1717 * options indicating how symbolic links are handled
1718 *
1719 * @return the file attributes
1720 *
1721 * @throws UnsupportedOperationException
1722 * if an attributes of the given type are not supported
1723 * @throws IOException
1724 * if an I/O error occurs
1725 * @throws SecurityException
1726 * In the case of the default provider, a security manager is
1727 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1728 * method is invoked to check read access to the file. If this
1729 * method is invoked to read security sensitive attributes then the
1730 * security manager may be invoke to check for additional permissions.
1731 */
1732 public static <A extends BasicFileAttributes> A readAttributes(Path path,
1733 Class<A> type,
1734 LinkOption... options)
1735 throws IOException
1736 {
1737 return provider(path).readAttributes(path, type, options);
1738 }
1739
1740 /**
1741 * Sets the value of a file attribute.
1742 *
1743 * <p> The {@code attribute} parameter identifies the attribute to be set
1744 * and takes the form:
1745 * <blockquote>
1746 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
1747 * </blockquote>
1748 * where square brackets [...] delineate an optional component and the
1749 * character {@code ':'} stands for itself.
1750 *
1751 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1752 * FileAttributeView} that identifies a set of file attributes. If not
1753 * specified then it defaults to {@code "basic"}, the name of the file
1754 * attribute view that identifies the basic set of file attributes common to
1755 * many file systems. <i>attribute-name</i> is the name of the attribute
1756 * within the set.
1757 *
1758 * <p> The {@code options} array may be used to indicate how symbolic links
1759 * are handled for the case that the file is a symbolic link. By default,
1760 * symbolic links are followed and the file attribute of the final target
1761 * of the link is set. If the option {@link LinkOption#NOFOLLOW_LINKS
1762 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1763 *
1764 * <p> <b>Usage Example:</b>
1765 * Suppose we want to set the DOS "hidden" attribute:
1766 * <pre>
1767 * Path path = ...
1768 * Files.setAttribute(path, "dos:hidden", true);
1769 * </pre>
1770 *
1771 * @param path
1772 * the path to the file
1773 * @param attribute
1774 * the attribute to set
1775 * @param value
1776 * the attribute value
1777 * @param options
1778 * options indicating how symbolic links are handled
1779 *
1780 * @return the {@code path} parameter
1781 *
1782 * @throws UnsupportedOperationException
1783 * if the attribute view is not available
1784 * @throws IllegalArgumentException
1785 * if the attribute name is not specified, or is not recognized, or
1786 * the attribute value is of the correct type but has an
1787 * inappropriate value
1788 * @throws ClassCastException
1789 * if the attribute value is not of the expected type or is a
1790 * collection containing elements that are not of the expected
1791 * type
1792 * @throws IOException
1793 * if an I/O error occurs
1794 * @throws SecurityException
1795 * In the case of the default provider, and a security manager is
1796 * installed, its {@link SecurityManager#checkWrite(String) checkWrite}
1797 * method denies write access to the file. If this method is invoked
1798 * to set security sensitive attributes then the security manager
1799 * may be invoked to check for additional permissions.
1800 */
1801 public static Path setAttribute(Path path, String attribute, Object value,
1802 LinkOption... options)
1803 throws IOException
1804 {
1805 provider(path).setAttribute(path, attribute, value, options);
1806 return path;
1807 }
1808
1809 /**
1810 * Reads the value of a file attribute.
1811 *
1812 * <p> The {@code attribute} parameter identifies the attribute to be read
1813 * and takes the form:
1814 * <blockquote>
1815 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
1816 * </blockquote>
1817 * where square brackets [...] delineate an optional component and the
1818 * character {@code ':'} stands for itself.
1819 *
1820 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1821 * FileAttributeView} that identifies a set of file attributes. If not
1822 * specified then it defaults to {@code "basic"}, the name of the file
1823 * attribute view that identifies the basic set of file attributes common to
1824 * many file systems. <i>attribute-name</i> is the name of the attribute.
1825 *
1826 * <p> The {@code options} array may be used to indicate how symbolic links
1827 * are handled for the case that the file is a symbolic link. By default,
1828 * symbolic links are followed and the file attribute of the final target
1829 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1830 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1831 *
1832 * <p> <b>Usage Example:</b>
1833 * Suppose we require the user ID of the file owner on a system that
1834 * supports a "{@code unix}" view:
1835 * <pre>
1836 * Path path = ...
1837 * int uid = (Integer)Files.getAttribute(path, "unix:uid");
1838 * </pre>
1839 *
1840 * @param path
1841 * the path to the file
1842 * @param attribute
1843 * the attribute to read
1844 * @param options
1845 * options indicating how symbolic links are handled
1846 *
1847 * @return the attribute value
1848 *
1849 * @throws UnsupportedOperationException
1850 * if the attribute view is not available
1851 * @throws IllegalArgumentException
1852 * if the attribute name is not specified or is not recognized
1853 * @throws IOException
1854 * if an I/O error occurs
1855 * @throws SecurityException
1856 * In the case of the default provider, and a security manager is
1857 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1858 * method denies read access to the file. If this method is invoked
1859 * to read security sensitive attributes then the security manager
1860 * may be invoked to check for additional permissions.
1861 */
1862 public static Object getAttribute(Path path, String attribute,
1863 LinkOption... options)
1864 throws IOException
1865 {
1866 // only one attribute should be read
1867 if (attribute.indexOf('*') >= 0 || attribute.indexOf(',') >= 0)
1868 throw new IllegalArgumentException(attribute);
1869 Map<String,Object> map = readAttributes(path, attribute, options);
1870 assert map.size() == 1;
1871 String name;
1872 int pos = attribute.indexOf(':');
1873 if (pos == -1) {
1874 name = attribute;
1875 } else {
1876 name = (pos == attribute.length()) ? "" : attribute.substring(pos+1);
1877 }
1878 return map.get(name);
1879 }
1880
1881 /**
1882 * Reads a set of file attributes as a bulk operation.
1883 *
1884 * <p> The {@code attributes} parameter identifies the attributes to be read
1885 * and takes the form:
1886 * <blockquote>
1887 * [<i>view-name</i><b>:</b>]<i>attribute-list</i>
1888 * </blockquote>
1889 * where square brackets [...] delineate an optional component and the
1890 * character {@code ':'} stands for itself.
1891 *
1892 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1893 * FileAttributeView} that identifies a set of file attributes. If not
1894 * specified then it defaults to {@code "basic"}, the name of the file
1895 * attribute view that identifies the basic set of file attributes common to
1896 * many file systems.
1897 *
1898 * <p> The <i>attribute-list</i> component is a comma separated list of
1899 * zero or more names of attributes to read. If the list contains the value
1900 * {@code "*"} then all attributes are read. Attributes that are not supported
1901 * are ignored and will not be present in the returned map. It is
1902 * implementation specific if all attributes are read as an atomic operation
1903 * with respect to other file system operations.
1904 *
1905 * <p> The following examples demonstrate possible values for the {@code
1906 * attributes} parameter:
1907 *
1908 * <blockquote>
1909 * <table border="0" summary="Possible values">
1910 * <tr>
1911 * <td> {@code "*"} </td>
1912 * <td> Read all {@link BasicFileAttributes basic-file-attributes}. </td>
1913 * </tr>
1914 * <tr>
1915 * <td> {@code "size,lastModifiedTime,lastAccessTime"} </td>
1916 * <td> Reads the file size, last modified time, and last access time
1917 * attributes. </td>
1918 * </tr>
1919 * <tr>
1920 * <td> {@code "posix:*"} </td>
1921 * <td> Read all {@link PosixFileAttributes POSIX-file-attributes}. </td>
1922 * </tr>
1923 * <tr>
1924 * <td> {@code "posix:permissions,owner,size"} </td>
1925 * <td> Reads the POSX file permissions, owner, and file size. </td>
1926 * </tr>
1927 * </table>
1928 * </blockquote>
1929 *
1930 * <p> The {@code options} array may be used to indicate how symbolic links
1931 * are handled for the case that the file is a symbolic link. By default,
1932 * symbolic links are followed and the file attribute of the final target
1933 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1934 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1935 *
1936 * @param path
1937 * the path to the file
1938 * @param attributes
1939 * the attributes to read
1940 * @param options
1941 * options indicating how symbolic links are handled
1942 *
1943 * @return a map of the attributes returned; The map's keys are the
1944 * attribute names, its values are the attribute values
1945 *
1946 * @throws UnsupportedOperationException
1947 * if the attribute view is not available
1948 * @throws IllegalArgumentException
1949 * if no attributes are specified or an unrecognized attributes is
1950 * specified
1951 * @throws IOException
1952 * if an I/O error occurs
1953 * @throws SecurityException
1954 * In the case of the default provider, and a security manager is
1955 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1956 * method denies read access to the file. If this method is invoked
1957 * to read security sensitive attributes then the security manager
1958 * may be invoke to check for additional permissions.
1959 */
1960 public static Map<String,Object> readAttributes(Path path, String attributes,
1961 LinkOption... options)
1962 throws IOException
1963 {
1964 return provider(path).readAttributes(path, attributes, options);
1965 }
1966
1967 /**
1968 * Returns a file's POSIX file permissions.
1969 *
1970 * <p> The {@code path} parameter is associated with a {@code FileSystem}
1971 * that supports the {@link PosixFileAttributeView}. This attribute view
1972 * provides access to file attributes commonly associated with files on file
1973 * systems used by operating systems that implement the Portable Operating
1974 * System Interface (POSIX) family of standards.
1975 *
1976 * <p> The {@code options} array may be used to indicate how symbolic links
1977 * are handled for the case that the file is a symbolic link. By default,
1978 * symbolic links are followed and the file attribute of the final target
1979 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1980 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1981 *
1982 * @param path
1983 * the path to the file
1984 * @param options
1985 * options indicating how symbolic links are handled
1986 *
1987 * @return the file permissions
1988 *
1989 * @throws UnsupportedOperationException
1990 * if the associated file system does not support the {@code
1991 * PosixFileAttributeView}
1992 * @throws IOException
1993 * if an I/O error occurs
1994 * @throws SecurityException
1995 * In the case of the default provider, a security manager is
1996 * installed, and it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
1997 * or its {@link SecurityManager#checkRead(String) checkRead} method
1998 * denies read access to the file.
1999 */
2000 public static Set<PosixFilePermission> getPosixFilePermissions(Path path,
2001 LinkOption... options)
2002 throws IOException
2003 {
2004 return readAttributes(path, PosixFileAttributes.class, options).permissions();
2005 }
2006
2007 /**
2008 * Sets a file's POSIX permissions.
2009 *
2010 * <p> The {@code path} parameter is associated with a {@code FileSystem}
2011 * that supports the {@link PosixFileAttributeView}. This attribute view
2012 * provides access to file attributes commonly associated with files on file
2013 * systems used by operating systems that implement the Portable Operating
2014 * System Interface (POSIX) family of standards.
2015 *
2016 * @param path
2017 * The path to the file
2018 * @param perms
2019 * The new set of permissions
2020 *
2021 * @return The path
2022 *
2023 * @throws UnsupportedOperationException
2024 * if the associated file system does not support the {@code
2025 * PosixFileAttributeView}
2026 * @throws ClassCastException
2027 * if the sets contains elements that are not of type {@code
2028 * PosixFilePermission}
2029 * @throws IOException
2030 * if an I/O error occurs
2031 * @throws SecurityException
2032 * In the case of the default provider, and a security manager is
2033 * installed, it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
2034 * or its {@link SecurityManager#checkWrite(String) checkWrite}
2035 * method denies write access to the file.
2036 */
2037 public static Path setPosixFilePermissions(Path path,
2038 Set<PosixFilePermission> perms)
2039 throws IOException
2040 {
2041 PosixFileAttributeView view =
2042 getFileAttributeView(path, PosixFileAttributeView.class);
2043 if (view == null)
2044 throw new UnsupportedOperationException();
2045 view.setPermissions(perms);
2046 return path;
2047 }
2048
2049 /**
2050 * Returns the owner of a file.
2051 *
2052 * <p> The {@code path} parameter is associated with a file system that
2053 * supports {@link FileOwnerAttributeView}. This file attribute view provides
2054 * access to a file attribute that is the owner of the file.
2055 *
2056 * @param path
2057 * The path to the file
2058 * @param options
2059 * options indicating how symbolic links are handled
2060 *
2061 * @return A user principal representing the owner of the file
2062 *
2063 * @throws UnsupportedOperationException
2064 * if the associated file system does not support the {@code
2065 * FileOwnerAttributeView}
2066 * @throws IOException
2067 * if an I/O error occurs
2068 * @throws SecurityException
2069 * In the case of the default provider, and a security manager is
2070 * installed, it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
2071 * or its {@link SecurityManager#checkRead(String) checkRead} method
2072 * denies read access to the file.
2073 */
2074 public static UserPrincipal getOwner(Path path, LinkOption... options) throws IOException {
2075 FileOwnerAttributeView view =
2076 getFileAttributeView(path, FileOwnerAttributeView.class, options);
2077 if (view == null)
2078 throw new UnsupportedOperationException();
2079 return view.getOwner();
2080 }
2081
2082 /**
2083 * Updates the file owner.
2084 *
2085 * <p> The {@code path} parameter is associated with a file system that
2086 * supports {@link FileOwnerAttributeView}. This file attribute view provides
2087 * access to a file attribute that is the owner of the file.
2088 *
2089 * <p> <b>Usage Example:</b>
2090 * Suppose we want to make "joe" the owner of a file:
2091 * <pre>
2092 * Path path = ...
2093 * UserPrincipalLookupService lookupService =
2094 * provider(path).getUserPrincipalLookupService();
2095 * UserPrincipal joe = lookupService.lookupPrincipalByName("joe");
2096 * Files.setOwner(path, joe);
2097 * </pre>
2098 *
2099 * @param path
2100 * The path to the file
2101 * @param owner
2102 * The new file owner
2103 *
2104 * @return The path
2105 *
2106 * @throws UnsupportedOperationException
2107 * if the associated file system does not support the {@code
2108 * FileOwnerAttributeView}
2109 * @throws IOException
2110 * if an I/O error occurs
2111 * @throws SecurityException
2112 * In the case of the default provider, and a security manager is
2113 * installed, it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
2114 * or its {@link SecurityManager#checkWrite(String) checkWrite}
2115 * method denies write access to the file.
2116 *
2117 * @see FileSystem#getUserPrincipalLookupService
2118 * @see java.nio.file.attribute.UserPrincipalLookupService
2119 */
2120 public static Path setOwner(Path path, UserPrincipal owner)
2121 throws IOException
2122 {
2123 FileOwnerAttributeView view =
2124 getFileAttributeView(path, FileOwnerAttributeView.class);
2125 if (view == null)
2126 throw new UnsupportedOperationException();
2127 view.setOwner(owner);
2128 return path;
2129 }
2130
2131 /**
2132 * Tests whether a file is a symbolic link.
2133 *
2134 * <p> Where it is required to distinguish an I/O exception from the case
2135 * that the file is not a symbolic link then the file attributes can be
2136 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2137 * readAttributes} method and the file type tested with the {@link
2138 * BasicFileAttributes#isSymbolicLink} method.
2139 *
2140 * @param path The path to the file
2141 *
2142 * @return {@code true} if the file is a symbolic link; {@code false} if
2143 * the file does not exist, is not a symbolic link, or it cannot
2144 * be determined if the file is a symbolic link or not.
2145 *
2146 * @throws SecurityException
2147 * In the case of the default provider, and a security manager is
2148 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2149 * method denies read access to the file.
2150 */
2151 public static boolean isSymbolicLink(Path path) {
2152 try {
2153 return readAttributes(path,
2154 BasicFileAttributes.class,
2155 LinkOption.NOFOLLOW_LINKS).isSymbolicLink();
2156 } catch (IOException ioe) {
2157 return false;
2158 }
2159 }
2160
2161 /**
2162 * Tests whether a file is a directory.
2163 *
2164 * <p> The {@code options} array may be used to indicate how symbolic links
2165 * are handled for the case that the file is a symbolic link. By default,
2166 * symbolic links are followed and the file attribute of the final target
2167 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2168 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2169 *
2170 * <p> Where it is required to distinguish an I/O exception from the case
2171 * that the file is not a directory then the file attributes can be
2172 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2173 * readAttributes} method and the file type tested with the {@link
2174 * BasicFileAttributes#isDirectory} method.
2175 *
2176 * @param path
2177 * the path to the file to test
2178 * @param options
2179 * options indicating how symbolic links are handled
2180 *
2181 * @return {@code true} if the file is a directory; {@code false} if
2182 * the file does not exist, is not a directory, or it cannot
2183 * be determined if the file is a directory or not.
2184 *
2185 * @throws SecurityException
2186 * In the case of the default provider, and a security manager is
2187 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2188 * method denies read access to the file.
2189 */
2190 public static boolean isDirectory(Path path, LinkOption... options) {
2191 try {
2192 return readAttributes(path, BasicFileAttributes.class, options).isDirectory();
2193 } catch (IOException ioe) {
2194 return false;
2195 }
2196 }
2197
2198 /**
2199 * Tests whether a file is a regular file with opaque content.
2200 *
2201 * <p> The {@code options} array may be used to indicate how symbolic links
2202 * are handled for the case that the file is a symbolic link. By default,
2203 * symbolic links are followed and the file attribute of the final target
2204 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2205 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2206 *
2207 * <p> Where it is required to distinguish an I/O exception from the case
2208 * that the file is not a regular file then the file attributes can be
2209 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2210 * readAttributes} method and the file type tested with the {@link
2211 * BasicFileAttributes#isRegularFile} method.
2212 *
2213 * @param path
2214 * the path to the file
2215 * @param options
2216 * options indicating how symbolic links are handled
2217 *
2218 * @return {@code true} if the file is a regular file; {@code false} if
2219 * the file does not exist, is not a regular file, or it
2220 * cannot be determined if the file is a regular file or not.
2221 *
2222 * @throws SecurityException
2223 * In the case of the default provider, and a security manager is
2224 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2225 * method denies read access to the file.
2226 */
2227 public static boolean isRegularFile(Path path, LinkOption... options) {
2228 try {
2229 return readAttributes(path, BasicFileAttributes.class, options).isRegularFile();
2230 } catch (IOException ioe) {
2231 return false;
2232 }
2233 }
2234
2235 /**
2236 * Returns a file's last modified time.
2237 *
2238 * <p> The {@code options} array may be used to indicate how symbolic links
2239 * are handled for the case that the file is a symbolic link. By default,
2240 * symbolic links are followed and the file attribute of the final target
2241 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2242 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2243 *
2244 * @param path
2245 * the path to the file
2246 * @param options
2247 * options indicating how symbolic links are handled
2248 *
2249 * @return a {@code FileTime} representing the time the file was last
2250 * modified, or an implementation specific default when a time
2251 * stamp to indicate the time of last modification is not supported
2252 * by the file system
2253 *
2254 * @throws IOException
2255 * if an I/O error occurs
2256 * @throws SecurityException
2257 * In the case of the default provider, and a security manager is
2258 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2259 * method denies read access to the file.
2260 *
2261 * @see BasicFileAttributes#lastModifiedTime
2262 */
2263 public static FileTime getLastModifiedTime(Path path, LinkOption... options)
2264 throws IOException
2265 {
2266 return readAttributes(path, BasicFileAttributes.class, options).lastModifiedTime();
2267 }
2268
2269 /**
2270 * Updates a file's last modified time attribute. The file time is converted
2271 * to the epoch and precision supported by the file system. Converting from
2272 * finer to coarser granularities result in precision loss. The behavior of
2273 * this method when attempting to set the last modified time when it is not
2274 * supported by the file system or is outside the range supported by the
2275 * underlying file store is not defined. It may or not fail by throwing an
2276 * {@code IOException}.
2277 *
2278 * <p> <b>Usage Example:</b>
2279 * Suppose we want to set the last modified time to the current time:
2280 * <pre>
2281 * Path path = ...
2282 * FileTime now = FileTime.fromMillis(System.currentTimeMillis());
2283 * Files.setLastModifiedTime(path, now);
2284 * </pre>
2285 *
2286 * @param path
2287 * the path to the file
2288 * @param time
2289 * the new last modified time
2290 *
2291 * @return the path
2292 *
2293 * @throws IOException
2294 * if an I/O error occurs
2295 * @throws SecurityException
2296 * In the case of the default provider, the security manager's {@link
2297 * SecurityManager#checkWrite(String) checkWrite} method is invoked
2298 * to check write access to file
2299 *
2300 * @see BasicFileAttributeView#setTimes
2301 */
2302 public static Path setLastModifiedTime(Path path, FileTime time)
2303 throws IOException
2304 {
2305 getFileAttributeView(path, BasicFileAttributeView.class)
2306 .setTimes(time, null, null);
2307 return path;
2308 }
2309
2310 /**
2311 * Returns the size of a file (in bytes). The size may differ from the
2312 * actual size on the file system due to compression, support for sparse
2313 * files, or other reasons. The size of files that are not {@link
2314 * #isRegularFile regular} files is implementation specific and
2315 * therefore unspecified.
2316 *
2317 * @param path
2318 * the path to the file
2319 *
2320 * @return the file size, in bytes
2321 *
2322 * @throws IOException
2323 * if an I/O error occurs
2324 * @throws SecurityException
2325 * In the case of the default provider, and a security manager is
2326 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2327 * method denies read access to the file.
2328 *
2329 * @see BasicFileAttributes#size
2330 */
2331 public static long size(Path path) throws IOException {
2332 return readAttributes(path, BasicFileAttributes.class).size();
2333 }
2334
2335 // -- Accessibility --
2336
2337 /**
2338 * Returns {@code false} if NOFOLLOW_LINKS is present.
2339 */
2340 private static boolean followLinks(LinkOption... options) {
2341 boolean followLinks = true;
2342 for (LinkOption opt: options) {
2343 if (opt == LinkOption.NOFOLLOW_LINKS) {
2344 followLinks = false;
2345 continue;
2346 }
2347 if (opt == null)
2348 throw new NullPointerException();
2349 throw new AssertionError("Should not get here");
2350 }
2351 return followLinks;
2352 }
2353
2354 /**
2355 * Tests whether a file exists.
2356 *
2357 * <p> The {@code options} parameter may be used to indicate how symbolic links
2358 * are handled for the case that the file is a symbolic link. By default,
2359 * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
2360 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2361 *
2362 * <p> Note that the result of this method is immediately outdated. If this
2363 * method indicates the file exists then there is no guarantee that a
2364 * subsequence access will succeed. Care should be taken when using this
2365 * method in security sensitive applications.
2366 *
2367 * @param path
2368 * the path to the file to test
2369 * @param options
2370 * options indicating how symbolic links are handled
2371 * .
2372 * @return {@code true} if the file exists; {@code false} if the file does
2373 * not exist or its existence cannot be determined.
2374 *
2375 * @throws SecurityException
2376 * In the case of the default provider, the {@link
2377 * SecurityManager#checkRead(String)} is invoked to check
2378 * read access to the file.
2379 *
2380 * @see #notExists
2381 */
2382 public static boolean exists(Path path, LinkOption... options) {
2383 try {
2384 if (followLinks(options)) {
2385 provider(path).checkAccess(path);
2386 } else {
2387 // attempt to read attributes without following links
2388 readAttributes(path, BasicFileAttributes.class,
2389 LinkOption.NOFOLLOW_LINKS);
2390 }
2391 // file exists
2392 return true;
2393 } catch (IOException x) {
2394 // does not exist or unable to determine if file exists
2395 return false;
2396 }
2397
2398 }
2399
2400 /**
2401 * Tests whether the file located by this path does not exist. This method
2402 * is intended for cases where it is required to take action when it can be
2403 * confirmed that a file does not exist.
2404 *
2405 * <p> The {@code options} parameter may be used to indicate how symbolic links
2406 * are handled for the case that the file is a symbolic link. By default,
2407 * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
2408 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2409 *
2410 * <p> Note that this method is not the complement of the {@link #exists
2411 * exists} method. Where it is not possible to determine if a file exists
2412 * or not then both methods return {@code false}. As with the {@code exists}
2413 * method, the result of this method is immediately outdated. If this
2414 * method indicates the file does exist then there is no guarantee that a
2415 * subsequence attempt to create the file will succeed. Care should be taken
2416 * when using this method in security sensitive applications.
2417 *
2418 * @param path
2419 * the path to the file to test
2420 * @param options
2421 * options indicating how symbolic links are handled
2422 *
2423 * @return {@code true} if the file does not exist; {@code false} if the
2424 * file exists or its existence cannot be determined
2425 *
2426 * @throws SecurityException
2427 * In the case of the default provider, the {@link
2428 * SecurityManager#checkRead(String)} is invoked to check
2429 * read access to the file.
2430 */
2431 public static boolean notExists(Path path, LinkOption... options) {
2432 try {
2433 if (followLinks(options)) {
2434 provider(path).checkAccess(path);
2435 } else {
2436 // attempt to read attributes without following links
2437 readAttributes(path, BasicFileAttributes.class,
2438 LinkOption.NOFOLLOW_LINKS);
2439 }
2440 // file exists
2441 return false;
2442 } catch (NoSuchFileException x) {
2443 // file confirmed not to exist
2444 return true;
2445 } catch (IOException x) {
2446 return false;
2447 }
2448 }
2449
2450 /**
2451 * Used by isReadbale, isWritable, isExecutable to test access to a file.
2452 */
2453 private static boolean isAccessible(Path path, AccessMode... modes) {
2454 try {
2455 provider(path).checkAccess(path, modes);
2456 return true;
2457 } catch (IOException x) {
2458 return false;
2459 }
2460 }
2461
2462 /**
2463 * Tests whether a file is readable. This method checks that a file exists
2464 * and that this Java virtual machine has appropriate privileges that would
2465 * allow it open the file for reading. Depending on the implementation, this
2466 * method may require to read file permissions, access control lists, or
2467 * other file attributes in order to check the effective access to the file.
2468 * Consequently, this method may not be atomic with respect to other file
2469 * system operations.
2470 *
2471 * <p> Note that the result of this method is immediately outdated, there is
2472 * no guarantee that a subsequent attempt to open the file for reading will
2473 * succeed (or even that it will access the same file). Care should be taken
2474 * when using this method in security sensitive applications.
2475 *
2476 * @param path
2477 * the path to the file to check
2478 *
2479 * @return {@code true} if the file exists and is readable; {@code false}
2480 * if the file does not exist, read access would be denied because
2481 * the Java virtual machine has insufficient privileges, or access
2482 * cannot be determined
2483 *
2484 * @throws SecurityException
2485 * In the case of the default provider, and a security manager is
2486 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2487 * is invoked to check read access to the file.
2488 */
2489 public static boolean isReadable(Path path) {
2490 return isAccessible(path, AccessMode.READ);
2491 }
2492
2493 /**
2494 * Tests whether a file is writable. This method checks that a file exists
2495 * and that this Java virtual machine has appropriate privileges that would
2496 * allow it open the file for writing. Depending on the implementation, this
2497 * method may require to read file permissions, access control lists, or
2498 * other file attributes in order to check the effective access to the file.
2499 * Consequently, this method may not be atomic with respect to other file
2500 * system operations.
2501 *
2502 * <p> Note that result of this method is immediately outdated, there is no
2503 * guarantee that a subsequent attempt to open the file for writing will
2504 * succeed (or even that it will access the same file). Care should be taken
2505 * when using this method in security sensitive applications.
2506 *
2507 * @param path
2508 * the path to the file to check
2509 *
2510 * @return {@code true} if the file exists and is writable; {@code false}
2511 * if the file does not exist, write access would be denied because
2512 * the Java virtual machine has insufficient privileges, or access
2513 * cannot be determined
2514 *
2515 * @throws SecurityException
2516 * In the case of the default provider, and a security manager is
2517 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2518 * is invoked to check write access to the file.
2519 */
2520 public static boolean isWritable(Path path) {
2521 return isAccessible(path, AccessMode.WRITE);
2522 }
2523
2524 /**
2525 * Tests whether a file is executable. This method checks that a file exists
2526 * and that this Java virtual machine has appropriate privileges to {@link
2527 * Runtime#exec execute} the file. The semantics may differ when checking
2528 * access to a directory. For example, on UNIX systems, checking for
2529 * execute access checks that the Java virtual machine has permission to
2530 * search the directory in order to access file or subdirectories.
2531 *
2532 * <p> Depending on the implementation, this method may require to read file
2533 * permissions, access control lists, or other file attributes in order to
2534 * check the effective access to the file. Consequently, this method may not
2535 * be atomic with respect to other file system operations.
2536 *
2537 * <p> Note that the result of this method is immediately outdated, there is
2538 * no guarantee that a subsequent attempt to execute the file will succeed
2539 * (or even that it will access the same file). Care should be taken when
2540 * using this method in security sensitive applications.
2541 *
2542 * @param path
2543 * the path to the file to check
2544 *
2545 * @return {@code true} if the file exists and is executable; {@code false}
2546 * if the file does not exist, execute access would be denied because
2547 * the Java virtual machine has insufficient privileges, or access
2548 * cannot be determined
2549 *
2550 * @throws SecurityException
2551 * In the case of the default provider, and a security manager is
2552 * installed, the {@link SecurityManager#checkExec(String)
2553 * checkExec} is invoked to check execute access to the file.
2554 */
2555 public static boolean isExecutable(Path path) {
2556 return isAccessible(path, AccessMode.EXECUTE);
2557 }
2558
2559 // -- Recursive operations --
2560
2561 /**
2562 * Walks a file tree.
2563 *
2564 * <p> This method walks a file tree rooted at a given starting file. The
2565 * file tree traversal is <em>depth-first</em> with the given {@link
2566 * FileVisitor} invoked for each file encountered. File tree traversal
2567 * completes when all accessible files in the tree have been visited, or a
2568 * visit method returns a result of {@link FileVisitResult#TERMINATE
2569 * TERMINATE}. Where a visit method terminates due an {@code IOException},
2570 * an uncaught error, or runtime exception, then the traversal is terminated
2571 * and the error or exception is propagated to the caller of this method.
2572 *
2573 * <p> For each file encountered this method attempts to read its {@link
2574 * java.nio.file.attribute.BasicFileAttributes}. If the file is not a
2575 * directory then the {@link FileVisitor#visitFile visitFile} method is
2576 * invoked with the file attributes. If the file attributes cannot be read,
2577 * due to an I/O exception, then the {@link FileVisitor#visitFileFailed
2578 * visitFileFailed} method is invoked with the I/O exception.
2579 *
2580 * <p> Where the file is a directory, and the directory could not be opened,
2581 * then the {@code visitFileFailed} method is invoked with the I/O exception,
2582 * after which, the file tree walk continues, by default, at the next
2583 * <em>sibling</em> of the directory.
2584 *
2585 * <p> Where the directory is opened successfully, then the entries in the
2586 * directory, and their <em>descendants</em> are visited. When all entries
2587 * have been visited, or an I/O error occurs during iteration of the
2588 * directory, then the directory is closed and the visitor's {@link
2589 * FileVisitor#postVisitDirectory postVisitDirectory} method is invoked.
2590 * The file tree walk then continues, by default, at the next <em>sibling</em>
2591 * of the directory.
2592 *
2593 * <p> By default, symbolic links are not automatically followed by this
2594 * method. If the {@code options} parameter contains the {@link
2595 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then symbolic links are
2596 * followed. When following links, and the attributes of the target cannot
2597 * be read, then this method attempts to get the {@code BasicFileAttributes}
2598 * of the link. If they can be read then the {@code visitFile} method is
2599 * invoked with the attributes of the link (otherwise the {@code visitFileFailed}
2600 * method is invoked as specified above).
2601 *
2602 * <p> If the {@code options} parameter contains the {@link
2603 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then this method keeps
2604 * track of directories visited so that cycles can be detected. A cycle
2605 * arises when there is an entry in a directory that is an ancestor of the
2606 * directory. Cycle detection is done by recording the {@link
2607 * java.nio.file.attribute.BasicFileAttributes#fileKey file-key} of directories,
2608 * or if file keys are not available, by invoking the {@link #isSameFile
2609 * isSameFile} method to test if a directory is the same file as an
2610 * ancestor. When a cycle is detected it is treated as an I/O error, and the
2611 * {@link FileVisitor#visitFileFailed visitFileFailed} method is invoked with
2612 * an instance of {@link FileSystemLoopException}.
2613 *
2614 * <p> The {@code maxDepth} parameter is the maximum number of levels of
2615 * directories to visit. A value of {@code 0} means that only the starting
2616 * file is visited, unless denied by the security manager. A value of
2617 * {@link Integer#MAX_VALUE MAX_VALUE} may be used to indicate that all
2618 * levels should be visited. The {@code visitFile} method is invoked for all
2619 * files, including directories, encountered at {@code maxDepth}, unless the
2620 * basic file attributes cannot be read, in which case the {@code
2621 * visitFileFailed} method is invoked.
2622 *
2623 * <p> If a visitor returns a result of {@code null} then {@code
2624 * NullPointerException} is thrown.
2625 *
2626 * <p> When a security manager is installed and it denies access to a file
2627 * (or directory), then it is ignored and the visitor is not invoked for
2628 * that file (or directory).
2629 *
2630 * @param start
2631 * the starting file
2632 * @param options
2633 * options to configure the traversal
2634 * @param maxDepth
2635 * the maximum number of directory levels to visit
2636 * @param visitor
2637 * the file visitor to invoke for each file
2638 *
2639 * @return the starting file
2640 *
2641 * @throws IllegalArgumentException
2642 * if the {@code maxDepth} parameter is negative
2643 * @throws SecurityException
2644 * If the security manager denies access to the starting file.
2645 * In the case of the default provider, the {@link
2646 * SecurityManager#checkRead(String) checkRead} method is invoked
2647 * to check read access to the directory.
2648 * @throws IOException
2649 * if an I/O error is thrown by a visitor method
2650 */
2651 public static Path walkFileTree(Path start,
2652 Set<FileVisitOption> options,
2653 int maxDepth,
2654 FileVisitor<? super Path> visitor)
2655 throws IOException
2656 {
2657 /**
2658 * Create a FileTreeWalker to walk the file tree, invoking the visitor
2659 * for each event.
2660 */
2661 try (FileTreeWalker walker = new FileTreeWalker(options, maxDepth)) {
2662 FileTreeWalker.Event ev = walker.walk(start);
2663 do {
2664 FileVisitResult result;
2665 switch (ev.type()) {
2666 case ENTRY :
2667 IOException ioe = ev.ioeException();
2668 if (ioe == null) {
2669 assert ev.attributes() != null;
2670 result = visitor.visitFile(ev.file(), ev.attributes());
2671 } else {
2672 result = visitor.visitFileFailed(ev.file(), ioe);
2673 }
2674 break;
2675
2676 case START_DIRECTORY :
2677 result = visitor.preVisitDirectory(ev.file(), ev.attributes());
2678
2679 // if SKIP_SIBLINGS and SKIP_SUBTREE is returned then
2680 // there shouldn't be any more events for the current
2681 // directory.
2682 if (result == FileVisitResult.SKIP_SUBTREE ||
2683 result == FileVisitResult.SKIP_SIBLINGS)
2684 walker.pop();
2685 break;
2686
2687 case END_DIRECTORY :
2688 result = visitor.postVisitDirectory(ev.file(), ev.ioeException());
2689
2690 // SKIP_SIBLINGS is a no-op for postVisitDirectory
2691 if (result == FileVisitResult.SKIP_SIBLINGS)
2692 result = FileVisitResult.CONTINUE;
2693 break;
2694
2695 default :
2696 throw new AssertionError("Should not get here");
2697 }
2698
2699 if (Objects.requireNonNull(result) != FileVisitResult.CONTINUE) {
2700 if (result == FileVisitResult.TERMINATE) {
2701 break;
2702 } else if (result == FileVisitResult.SKIP_SIBLINGS) {
2703 walker.skipRemainingSiblings();
2704 }
2705 }
2706 ev = walker.next();
2707 } while (ev != null);
2708 }
2709
2710 return start;
2711 }
2712
2713 /**
2714 * Walks a file tree.
2715 *
2716 * <p> This method works as if invoking it were equivalent to evaluating the
2717 * expression:
2718 * <blockquote><pre>
2719 * walkFileTree(start, EnumSet.noneOf(FileVisitOption.class), Integer.MAX_VALUE, visitor)
2720 * </pre></blockquote>
2721 * In other words, it does not follow symbolic links, and visits all levels
2722 * of the file tree.
2723 *
2724 * @param start
2725 * the starting file
2726 * @param visitor
2727 * the file visitor to invoke for each file
2728 *
2729 * @return the starting file
2730 *
2731 * @throws SecurityException
2732 * If the security manager denies access to the starting file.
2733 * In the case of the default provider, the {@link
2734 * SecurityManager#checkRead(String) checkRead} method is invoked
2735 * to check read access to the directory.
2736 * @throws IOException
2737 * if an I/O error is thrown by a visitor method
2738 */
2739 public static Path walkFileTree(Path start, FileVisitor<? super Path> visitor)
2740 throws IOException
2741 {
2742 return walkFileTree(start,
2743 EnumSet.noneOf(FileVisitOption.class),
2744 Integer.MAX_VALUE,
2745 visitor);
2746 }
2747
2748
2749 // -- Utility methods for simple usages --
2750
2751 // buffer size used for reading and writing
2752 private static final int BUFFER_SIZE = 8192;
2753
2754 /**
2755 * Opens a file for reading, returning a {@code BufferedReader} that may be
2756 * used to read text from the file in an efficient manner. Bytes from the
2757 * file are decoded into characters using the specified charset. Reading
2758 * commences at the beginning of the file.
2759 *
2760 * <p> The {@code Reader} methods that read from the file throw {@code
2761 * IOException} if a malformed or unmappable byte sequence is read.
2762 *
2763 * @param path
2764 * the path to the file
2765 * @param cs
2766 * the charset to use for decoding
2767 *
2768 * @return a new buffered reader, with default buffer size, to read text
2769 * from the file
2770 *
2771 * @throws IOException
2772 * if an I/O error occurs opening the file
2773 * @throws SecurityException
2774 * In the case of the default provider, and a security manager is
2775 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2776 * method is invoked to check read access to the file.
2777 *
2778 * @see #readAllLines
2779 */
2780 public static BufferedReader newBufferedReader(Path path, Charset cs)
2781 throws IOException
2782 {
2783 CharsetDecoder decoder = cs.newDecoder();
2784 Reader reader = new InputStreamReader(newInputStream(path), decoder);
2785 return new BufferedReader(reader);
2786 }
2787
2788 /**
2789 * Opens a file for reading, returning a {@code BufferedReader} to read text
2790 * from the file in an efficient manner. Bytes from the file are decoded into
2791 * characters using the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset
2792 * charset}.
2793 *
2794 * <p> This method works as if invoking it were equivalent to evaluating the
2795 * expression:
2796 * <pre>{@code
2797 * Files.newBufferedReader(path, StandardCharsets.UTF_8)
2798 * }</pre>
2799 *
2800 * @param path
2801 * the path to the file
2802 *
2803 * @return a new buffered reader, with default buffer size, to read text
2804 * from the file
2805 *
2806 * @throws IOException
2807 * if an I/O error occurs opening the file
2808 * @throws SecurityException
2809 * In the case of the default provider, and a security manager is
2810 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2811 * method is invoked to check read access to the file.
2812 *
2813 * @since 1.8
2814 */
2815 public static BufferedReader newBufferedReader(Path path) throws IOException {
2816 return newBufferedReader(path, StandardCharsets.UTF_8);
2817 }
2818
2819 /**
2820 * Opens or creates a file for writing, returning a {@code BufferedWriter}
2821 * that may be used to write text to the file in an efficient manner.
2822 * The {@code options} parameter specifies how the the file is created or
2823 * opened. If no options are present then this method works as if the {@link
2824 * StandardOpenOption#CREATE CREATE}, {@link
2825 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
2826 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
2827 * opens the file for writing, creating the file if it doesn't exist, or
2828 * initially truncating an existing {@link #isRegularFile regular-file} to
2829 * a size of {@code 0} if it exists.
2830 *
2831 * <p> The {@code Writer} methods to write text throw {@code IOException}
2832 * if the text cannot be encoded using the specified charset.
2833 *
2834 * @param path
2835 * the path to the file
2836 * @param cs
2837 * the charset to use for encoding
2838 * @param options
2839 * options specifying how the file is opened
2840 *
2841 * @return a new buffered writer, with default buffer size, to write text
2842 * to the file
2843 *
2844 * @throws IOException
2845 * if an I/O error occurs opening or creating the file
2846 * @throws UnsupportedOperationException
2847 * if an unsupported option is specified
2848 * @throws SecurityException
2849 * In the case of the default provider, and a security manager is
2850 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2851 * method is invoked to check write access to the file.
2852 *
2853 * @see #write(Path,Iterable,Charset,OpenOption[])
2854 */
2855 public static BufferedWriter newBufferedWriter(Path path, Charset cs,
2856 OpenOption... options)
2857 throws IOException
2858 {
2859 CharsetEncoder encoder = cs.newEncoder();
2860 Writer writer = new OutputStreamWriter(newOutputStream(path, options), encoder);
2861 return new BufferedWriter(writer);
2862 }
2863
2864 /**
2865 * Opens or creates a file for writing, returning a {@code BufferedWriter}
2866 * to write text to the file in an efficient manner. The text is encoded
2867 * into bytes for writing using the {@link StandardCharsets#UTF_8 UTF-8}
2868 * {@link Charset charset}.
2869 *
2870 * <p> This method works as if invoking it were equivalent to evaluating the
2871 * expression:
2872 * <pre>{@code
2873 * Files.newBufferedWriter(path, StandardCharsets.UTF_8, options)
2874 * }</pre>
2875 *
2876 * @param path
2877 * the path to the file
2878 * @param options
2879 * options specifying how the file is opened
2880 *
2881 * @return a new buffered writer, with default buffer size, to write text
2882 * to the file
2883 *
2884 * @throws IOException
2885 * if an I/O error occurs opening or creating the file
2886 * @throws UnsupportedOperationException
2887 * if an unsupported option is specified
2888 * @throws SecurityException
2889 * In the case of the default provider, and a security manager is
2890 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2891 * method is invoked to check write access to the file.
2892 *
2893 * @since 1.8
2894 */
2895 public static BufferedWriter newBufferedWriter(Path path, OpenOption... options) throws IOException {
2896 return newBufferedWriter(path, StandardCharsets.UTF_8, options);
2897 }
2898
2899 /**
2900 * Reads all bytes from an input stream and writes them to an output stream.
2901 */
2902 private static long copy(InputStream source, OutputStream sink)
2903 throws IOException
2904 {
2905 long nread = 0L;
2906 byte[] buf = new byte[BUFFER_SIZE];
2907 int n;
2908 while ((n = source.read(buf)) > 0) {
2909 sink.write(buf, 0, n);
2910 nread += n;
2911 }
2912 return nread;
2913 }
2914
2915 /**
2916 * Copies all bytes from an input stream to a file. On return, the input
2917 * stream will be at end of stream.
2918 *
2919 * <p> By default, the copy fails if the target file already exists or is a
2920 * symbolic link. If the {@link StandardCopyOption#REPLACE_EXISTING
2921 * REPLACE_EXISTING} option is specified, and the target file already exists,
2922 * then it is replaced if it is not a non-empty directory. If the target
2923 * file exists and is a symbolic link, then the symbolic link is replaced.
2924 * In this release, the {@code REPLACE_EXISTING} option is the only option
2925 * required to be supported by this method. Additional options may be
2926 * supported in future releases.
2927 *
2928 * <p> If an I/O error occurs reading from the input stream or writing to
2929 * the file, then it may do so after the target file has been created and
2930 * after some bytes have been read or written. Consequently the input
2931 * stream may not be at end of stream and may be in an inconsistent state.
2932 * It is strongly recommended that the input stream be promptly closed if an
2933 * I/O error occurs.
2934 *
2935 * <p> This method may block indefinitely reading from the input stream (or
2936 * writing to the file). The behavior for the case that the input stream is
2937 * <i>asynchronously closed</i> or the thread interrupted during the copy is
2938 * highly input stream and file system provider specific and therefore not
2939 * specified.
2940 *
2941 * <p> <b>Usage example</b>: Suppose we want to capture a web page and save
2942 * it to a file:
2943 * <pre>
2944 * Path path = ...
2945 * URI u = URI.create("http://java.sun.com/");
2946 * try (InputStream in = u.toURL().openStream()) {
2947 * Files.copy(in, path);
2948 * }
2949 * </pre>
2950 *
2951 * @param in
2952 * the input stream to read from
2953 * @param target
2954 * the path to the file
2955 * @param options
2956 * options specifying how the copy should be done
2957 *
2958 * @return the number of bytes read or written
2959 *
2960 * @throws IOException
2961 * if an I/O error occurs when reading or writing
2962 * @throws FileAlreadyExistsException
2963 * if the target file exists but cannot be replaced because the
2964 * {@code REPLACE_EXISTING} option is not specified <i>(optional
2965 * specific exception)</i>
2966 * @throws DirectoryNotEmptyException
2967 * the {@code REPLACE_EXISTING} option is specified but the file
2968 * cannot be replaced because it is a non-empty directory
2969 * <i>(optional specific exception)</i> *
2970 * @throws UnsupportedOperationException
2971 * if {@code options} contains a copy option that is not supported
2972 * @throws SecurityException
2973 * In the case of the default provider, and a security manager is
2974 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2975 * method is invoked to check write access to the file. Where the
2976 * {@code REPLACE_EXISTING} option is specified, the security
2977 * manager's {@link SecurityManager#checkDelete(String) checkDelete}
2978 * method is invoked to check that an existing file can be deleted.
2979 */
2980 public static long copy(InputStream in, Path target, CopyOption... options)
2981 throws IOException
2982 {
2983 // ensure not null before opening file
2984 Objects.requireNonNull(in);
2985
2986 // check for REPLACE_EXISTING
2987 boolean replaceExisting = false;
2988 for (CopyOption opt: options) {
2989 if (opt == StandardCopyOption.REPLACE_EXISTING) {
2990 replaceExisting = true;
2991 } else {
2992 if (opt == null) {
2993 throw new NullPointerException("options contains 'null'");
2994 } else {
2995 throw new UnsupportedOperationException(opt + " not supported");
2996 }
2997 }
2998 }
2999
3000 // attempt to delete an existing file
3001 SecurityException se = null;
3002 if (replaceExisting) {
3003 try {
3004 deleteIfExists(target);
3005 } catch (SecurityException x) {
3006 se = x;
3007 }
3008 }
3009
3010 // attempt to create target file. If it fails with
3011 // FileAlreadyExistsException then it may be because the security
3012 // manager prevented us from deleting the file, in which case we just
3013 // throw the SecurityException.
3014 OutputStream ostream;
3015 try {
3016 ostream = newOutputStream(target, StandardOpenOption.CREATE_NEW,
3017 StandardOpenOption.WRITE);
3018 } catch (FileAlreadyExistsException x) {
3019 if (se != null)
3020 throw se;
3021 // someone else won the race and created the file
3022 throw x;
3023 }
3024
3025 // do the copy
3026 try (OutputStream out = ostream) {
3027 return copy(in, out);
3028 }
3029 }
3030
3031 /**
3032 * Copies all bytes from a file to an output stream.
3033 *
3034 * <p> If an I/O error occurs reading from the file or writing to the output
3035 * stream, then it may do so after some bytes have been read or written.
3036 * Consequently the output stream may be in an inconsistent state. It is
3037 * strongly recommended that the output stream be promptly closed if an I/O
3038 * error occurs.
3039 *
3040 * <p> This method may block indefinitely writing to the output stream (or
3041 * reading from the file). The behavior for the case that the output stream
3042 * is <i>asynchronously closed</i> or the thread interrupted during the copy
3043 * is highly output stream and file system provider specific and therefore
3044 * not specified.
3045 *
3046 * <p> Note that if the given output stream is {@link java.io.Flushable}
3047 * then its {@link java.io.Flushable#flush flush} method may need to invoked
3048 * after this method completes so as to flush any buffered output.
3049 *
3050 * @param source
3051 * the path to the file
3052 * @param out
3053 * the output stream to write to
3054 *
3055 * @return the number of bytes read or written
3056 *
3057 * @throws IOException
3058 * if an I/O error occurs when reading or writing
3059 * @throws SecurityException
3060 * In the case of the default provider, and a security manager is
3061 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3062 * method is invoked to check read access to the file.
3063 */
3064 public static long copy(Path source, OutputStream out) throws IOException {
3065 // ensure not null before opening file
3066 Objects.requireNonNull(out);
3067
3068 try (InputStream in = newInputStream(source)) {
3069 return copy(in, out);
3070 }
3071 }
3072
3073 /**
3074 * The maximum size of array to allocate.
3075 * Some VMs reserve some header words in an array.
3076 * Attempts to allocate larger arrays may result in
3077 * OutOfMemoryError: Requested array size exceeds VM limit
3078 */
3079 private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
3080
3081 /**
3082 * Reads all the bytes from an input stream. Uses {@code initialSize} as a hint
3083 * about how many bytes the stream will have.
3084 *
3085 * @param source
3086 * the input stream to read from
3087 * @param initialSize
3088 * the initial size of the byte array to allocate
3089 *
3090 * @return a byte array containing the bytes read from the file
3091 *
3092 * @throws IOException
3093 * if an I/O error occurs reading from the stream
3094 * @throws OutOfMemoryError
3095 * if an array of the required size cannot be allocated
3096 */
3097 private static byte[] read(InputStream source, int initialSize) throws IOException {
3098 int capacity = initialSize;
3099 byte[] buf = new byte[capacity];
3100 int nread = 0;
3101 int n;
3102 for (;;) {
3103 // read to EOF which may read more or less than initialSize (eg: file
3104 // is truncated while we are reading)
3105 while ((n = source.read(buf, nread, capacity - nread)) > 0)
3106 nread += n;
3107
3108 // if last call to source.read() returned -1, we are done
3109 // otherwise, try to read one more byte; if that failed we're done too
3110 if (n < 0 || (n = source.read()) < 0)
3111 break;
3112
3113 // one more byte was read; need to allocate a larger buffer
3114 if (capacity <= MAX_BUFFER_SIZE - capacity) {
3115 capacity = Math.max(capacity << 1, BUFFER_SIZE);
3116 } else {
3117 if (capacity == MAX_BUFFER_SIZE)
3118 throw new OutOfMemoryError("Required array size too large");
3119 capacity = MAX_BUFFER_SIZE;
3120 }
3121 buf = Arrays.copyOf(buf, capacity);
3122 buf[nread++] = (byte)n;
3123 }
3124 return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
3125 }
3126
3127 /**
3128 * Reads all the bytes from a file. The method ensures that the file is
3129 * closed when all bytes have been read or an I/O error, or other runtime
3130 * exception, is thrown.
3131 *
3132 * <p> Note that this method is intended for simple cases where it is
3133 * convenient to read all bytes into a byte array. It is not intended for
3134 * reading in large files.
3135 *
3136 * @param path
3137 * the path to the file
3138 *
3139 * @return a byte array containing the bytes read from the file
3140 *
3141 * @throws IOException
3142 * if an I/O error occurs reading from the stream
3143 * @throws OutOfMemoryError
3144 * if an array of the required size cannot be allocated, for
3145 * example the file is larger that {@code 2GB}
3146 * @throws SecurityException
3147 * In the case of the default provider, and a security manager is
3148 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3149 * method is invoked to check read access to the file.
3150 */
3151 public static byte[] readAllBytes(Path path) throws IOException {
3152 try (SeekableByteChannel sbc = Files.newByteChannel(path);
3153 InputStream in = Channels.newInputStream(sbc)) {
3154 long size = sbc.size();
3155 if (size > (long)MAX_BUFFER_SIZE)
3156 throw new OutOfMemoryError("Required array size too large");
3157
3158 return read(in, (int)size);
3159 }
3160 }
3161
3162 /**
3163 * Read all lines from a file. This method ensures that the file is
3164 * closed when all bytes have been read or an I/O error, or other runtime
3165 * exception, is thrown. Bytes from the file are decoded into characters
3166 * using the specified charset.
3167 *
3168 * <p> This method recognizes the following as line terminators:
3169 * <ul>
3170 * <li> <code>\u000D</code> followed by <code>\u000A</code>,
3171 * CARRIAGE RETURN followed by LINE FEED </li>
3172 * <li> <code>\u000A</code>, LINE FEED </li>
3173 * <li> <code>\u000D</code>, CARRIAGE RETURN </li>
3174 * </ul>
3175 * <p> Additional Unicode line terminators may be recognized in future
3176 * releases.
3177 *
3178 * <p> Note that this method is intended for simple cases where it is
3179 * convenient to read all lines in a single operation. It is not intended
3180 * for reading in large files.
3181 *
3182 * @param path
3183 * the path to the file
3184 * @param cs
3185 * the charset to use for decoding
3186 *
3187 * @return the lines from the file as a {@code List}; whether the {@code
3188 * List} is modifiable or not is implementation dependent and
3189 * therefore not specified
3190 *
3191 * @throws IOException
3192 * if an I/O error occurs reading from the file or a malformed or
3193 * unmappable byte sequence is read
3194 * @throws SecurityException
3195 * In the case of the default provider, and a security manager is
3196 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3197 * method is invoked to check read access to the file.
3198 *
3199 * @see #newBufferedReader
3200 */
3201 public static List<String> readAllLines(Path path, Charset cs) throws IOException {
3202 try (BufferedReader reader = newBufferedReader(path, cs)) {
3203 List<String> result = new ArrayList<>();
3204 for (;;) {
3205 String line = reader.readLine();
3206 if (line == null)
3207 break;
3208 result.add(line);
3209 }
3210 return result;
3211 }
3212 }
3213
3214 /**
3215 * Read all lines from a file. Bytes from the file are decoded into characters
3216 * using the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
3217 *
3218 * <p> This method works as if invoking it were equivalent to evaluating the
3219 * expression:
3220 * <pre>{@code
3221 * Files.readAllLines(path, StandardCharsets.UTF_8)
3222 * }</pre>
3223 *
3224 * @param path
3225 * the path to the file
3226 *
3227 * @return the lines from the file as a {@code List}; whether the {@code
3228 * List} is modifiable or not is implementation dependent and
3229 * therefore not specified
3230 *
3231 * @throws IOException
3232 * if an I/O error occurs reading from the file or a malformed or
3233 * unmappable byte sequence is read
3234 * @throws SecurityException
3235 * In the case of the default provider, and a security manager is
3236 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3237 * method is invoked to check read access to the file.
3238 *
3239 * @since 1.8
3240 */
3241 public static List<String> readAllLines(Path path) throws IOException {
3242 return readAllLines(path, StandardCharsets.UTF_8);
3243 }
3244
3245 /**
3246 * Writes bytes to a file. The {@code options} parameter specifies how the
3247 * the file is created or opened. If no options are present then this method
3248 * works as if the {@link StandardOpenOption#CREATE CREATE}, {@link
3249 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3250 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3251 * opens the file for writing, creating the file if it doesn't exist, or
3252 * initially truncating an existing {@link #isRegularFile regular-file} to
3253 * a size of {@code 0}. All bytes in the byte array are written to the file.
3254 * The method ensures that the file is closed when all bytes have been
3255 * written (or an I/O error or other runtime exception is thrown). If an I/O
3256 * error occurs then it may do so after the file has created or truncated,
3257 * or after some bytes have been written to the file.
3258 *
3259 * <p> <b>Usage example</b>: By default the method creates a new file or
3260 * overwrites an existing file. Suppose you instead want to append bytes
3261 * to an existing file:
3262 * <pre>
3263 * Path path = ...
3264 * byte[] bytes = ...
3265 * Files.write(path, bytes, StandardOpenOption.APPEND);
3266 * </pre>
3267 *
3268 * @param path
3269 * the path to the file
3270 * @param bytes
3271 * the byte array with the bytes to write
3272 * @param options
3273 * options specifying how the file is opened
3274 *
3275 * @return the path
3276 *
3277 * @throws IOException
3278 * if an I/O error occurs writing to or creating the file
3279 * @throws UnsupportedOperationException
3280 * if an unsupported option is specified
3281 * @throws SecurityException
3282 * In the case of the default provider, and a security manager is
3283 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3284 * method is invoked to check write access to the file.
3285 */
3286 public static Path write(Path path, byte[] bytes, OpenOption... options)
3287 throws IOException
3288 {
3289 // ensure bytes is not null before opening file
3290 Objects.requireNonNull(bytes);
3291
3292 try (OutputStream out = Files.newOutputStream(path, options)) {
3293 int len = bytes.length;
3294 int rem = len;
3295 while (rem > 0) {
3296 int n = Math.min(rem, BUFFER_SIZE);
3297 out.write(bytes, (len-rem), n);
3298 rem -= n;
3299 }
3300 }
3301 return path;
3302 }
3303
3304 /**
3305 * Write lines of text to a file. Each line is a char sequence and is
3306 * written to the file in sequence with each line terminated by the
3307 * platform's line separator, as defined by the system property {@code
3308 * line.separator}. Characters are encoded into bytes using the specified
3309 * charset.
3310 *
3311 * <p> The {@code options} parameter specifies how the the file is created
3312 * or opened. If no options are present then this method works as if the
3313 * {@link StandardOpenOption#CREATE CREATE}, {@link
3314 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3315 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3316 * opens the file for writing, creating the file if it doesn't exist, or
3317 * initially truncating an existing {@link #isRegularFile regular-file} to
3318 * a size of {@code 0}. The method ensures that the file is closed when all
3319 * lines have been written (or an I/O error or other runtime exception is
3320 * thrown). If an I/O error occurs then it may do so after the file has
3321 * created or truncated, or after some bytes have been written to the file.
3322 *
3323 * @param path
3324 * the path to the file
3325 * @param lines
3326 * an object to iterate over the char sequences
3327 * @param cs
3328 * the charset to use for encoding
3329 * @param options
3330 * options specifying how the file is opened
3331 *
3332 * @return the path
3333 *
3334 * @throws IOException
3335 * if an I/O error occurs writing to or creating the file, or the
3336 * text cannot be encoded using the specified charset
3337 * @throws UnsupportedOperationException
3338 * if an unsupported option is specified
3339 * @throws SecurityException
3340 * In the case of the default provider, and a security manager is
3341 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3342 * method is invoked to check write access to the file.
3343 */
3344 public static Path write(Path path, Iterable<? extends CharSequence> lines,
3345 Charset cs, OpenOption... options)
3346 throws IOException
3347 {
3348 // ensure lines is not null before opening file
3349 Objects.requireNonNull(lines);
3350 CharsetEncoder encoder = cs.newEncoder();
3351 OutputStream out = newOutputStream(path, options);
3352 try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, encoder))) {
3353 for (CharSequence line: lines) {
3354 writer.append(line);
3355 writer.newLine();
3356 }
3357 }
3358 return path;
3359 }
3360
3361 /**
3362 * Write lines of text to a file. Characters are encoded into bytes using
3363 * the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
3364 *
3365 * <p> This method works as if invoking it were equivalent to evaluating the
3366 * expression:
3367 * <pre>{@code
3368 * Files.write(path, lines, StandardCharsets.UTF_8, options);
3369 * }</pre>
3370 *
3371 * @param path
3372 * the path to the file
3373 * @param lines
3374 * an object to iterate over the char sequences
3375 * @param options
3376 * options specifying how the file is opened
3377 *
3378 * @return the path
3379 *
3380 * @throws IOException
3381 * if an I/O error occurs writing to or creating the file, or the
3382 * text cannot be encoded as {@code UTF-8}
3383 * @throws UnsupportedOperationException
3384 * if an unsupported option is specified
3385 * @throws SecurityException
3386 * In the case of the default provider, and a security manager is
3387 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3388 * method is invoked to check write access to the file.
3389 *
3390 * @since 1.8
3391 */
3392 public static Path write(Path path,
3393 Iterable<? extends CharSequence> lines,
3394 OpenOption... options)
3395 throws IOException
3396 {
3397 return write(path, lines, StandardCharsets.UTF_8, options);
3398 }
3399
3400 // -- Stream APIs --
3401
3402 /**
3403 * Return a lazily populated {@code Stream}, the elements of
3404 * which are the entries in the directory. The listing is not recursive.
3405 *
3406 * <p> The elements of the stream are {@link Path} objects that are
3407 * obtained as if by {@link Path#resolve(Path) resolving} the name of the
3408 * directory entry against {@code dir}. Some file systems maintain special
3409 * links to the directory itself and the directory's parent directory.
3410 * Entries representing these links are not included.
3411 *
3412 * <p> The stream is <i>weakly consistent</i>. It is thread safe but does
3413 * not freeze the directory while iterating, so it may (or may not)
3414 * reflect updates to the directory that occur after returning from this
3415 * method.
3416 *
3417 * <p> The returned stream encapsulates a {@link DirectoryStream}.
3418 * If timely disposal of file system resources is required, the
3419 * {@code try}-with-resources construct should be used to ensure that the
3420 * stream's {@link Stream#close close} method is invoked after the stream
3421 * operations are completed.
3422 *
3423 * <p> Operating on a closed stream behaves as if the end of stream
3424 * has been reached. Due to read-ahead, one or more elements may be
3425 * returned after the stream has been closed.
3426 *
3427 * <p> If an {@link IOException} is thrown when accessing the directory
3428 * after this method has returned, it is wrapped in an {@link
3429 * UncheckedIOException} which will be thrown from the method that caused
3430 * the access to take place.
3431 *
3432 * @param dir The path to the directory
3433 *
3434 * @return The {@code Stream} describing the content of the
3435 * directory
3436 *
3437 * @throws NotDirectoryException
3438 * if the file could not otherwise be opened because it is not
3439 * a directory <i>(optional specific exception)</i>
3440 * @throws IOException
3441 * if an I/O error occurs when opening the directory
3442 * @throws SecurityException
3443 * In the case of the default provider, and a security manager is
3444 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3445 * method is invoked to check read access to the directory.
3446 *
3447 * @see #newDirectoryStream(Path)
3448 * @since 1.8
3449 */
3450 public static Stream<Path> list(Path dir) throws IOException {
3451 DirectoryStream<Path> ds = Files.newDirectoryStream(dir);
3452 try {
3453 final Iterator<Path> delegate = ds.iterator();
3454
3455 // Re-wrap DirectoryIteratorException to UncheckedIOException
3456 Iterator<Path> it = new Iterator<Path>() {
3457 @Override
3458 public boolean hasNext() {
3459 try {
3460 return delegate.hasNext();
3461 } catch (DirectoryIteratorException e) {
3462 throw new UncheckedIOException(e.getCause());
3463 }
3464 }
3465 @Override
3466 public Path next() {
3467 try {
3468 return delegate.next();
3469 } catch (DirectoryIteratorException e) {
3470 throw new UncheckedIOException(e.getCause());
3471 }
3472 }
3473 };
3474
3475 return StreamSupport.stream(Spliterators.spliteratorUnknownSize(it, Spliterator.DISTINCT), false)
3476 .onClose(asUncheckedRunnable(ds));
3477 } catch (Error|RuntimeException e) {
3478 try {
3479 ds.close();
3480 } catch (IOException ex) {
3481 try {
3482 e.addSuppressed(ex);
3483 } catch (Throwable ignore) {}
3484 }
3485 throw e;
3486 }
3487 }
3488
3489 /**
3490 * Return a {@code Stream} that is lazily populated with {@code
3491 * Path} by walking the file tree rooted at a given starting file. The
3492 * file tree is traversed <em>depth-first</em>, the elements in the stream
3493 * are {@link Path} objects that are obtained as if by {@link
3494 * Path#resolve(Path) resolving} the relative path against {@code start}.
3495 *
3496 * <p> The {@code stream} walks the file tree as elements are consumed.
3497 * The {@code Stream} returned is guaranteed to have at least one
3498 * element, the starting file itself. For each file visited, the stream
3499 * attempts to read its {@link BasicFileAttributes}. If the file is a
3500 * directory and can be opened successfully, entries in the directory, and
3501 * their <em>descendants</em> will follow the directory in the stream as
3502 * they are encountered. When all entries have been visited, then the
3503 * directory is closed. The file tree walk then continues at the next
3504 * <em>sibling</em> of the directory.
3505 *
3506 * <p> The stream is <i>weakly consistent</i>. It does not freeze the
3507 * file tree while iterating, so it may (or may not) reflect updates to
3508 * the file tree that occur after returned from this method.
3509 *
3510 * <p> By default, symbolic links are not automatically followed by this
3511 * method. If the {@code options} parameter contains the {@link
3512 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then symbolic links are
3513 * followed. When following links, and the attributes of the target cannot
3514 * be read, then this method attempts to get the {@code BasicFileAttributes}
3515 * of the link.
3516 *
3517 * <p> If the {@code options} parameter contains the {@link
3518 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then the stream keeps
3519 * track of directories visited so that cycles can be detected. A cycle
3520 * arises when there is an entry in a directory that is an ancestor of the
3521 * directory. Cycle detection is done by recording the {@link
3522 * java.nio.file.attribute.BasicFileAttributes#fileKey file-key} of directories,
3523 * or if file keys are not available, by invoking the {@link #isSameFile
3524 * isSameFile} method to test if a directory is the same file as an
3525 * ancestor. When a cycle is detected it is treated as an I/O error with
3526 * an instance of {@link FileSystemLoopException}.
3527 *
3528 * <p> The {@code maxDepth} parameter is the maximum number of levels of
3529 * directories to visit. A value of {@code 0} means that only the starting
3530 * file is visited, unless denied by the security manager. A value of
3531 * {@link Integer#MAX_VALUE MAX_VALUE} may be used to indicate that all
3532 * levels should be visited.
3533 *
3534 * <p> When a security manager is installed and it denies access to a file
3535 * (or directory), then it is ignored and not included in the stream.
3536 *
3537 * <p> The returned stream encapsulates one or more {@link DirectoryStream}s.
3538 * If timely disposal of file system resources is required, the
3539 * {@code try}-with-resources construct should be used to ensure that the
3540 * stream's {@link Stream#close close} method is invoked after the stream
3541 * operations are completed. Operating on a closed stream will result in an
3542 * {@link java.lang.IllegalStateException}.
3543 *
3544 * <p> If an {@link IOException} is thrown when accessing the directory
3545 * after this method has returned, it is wrapped in an {@link
3546 * UncheckedIOException} which will be thrown from the method that caused
3547 * the access to take place.
3548 *
3549 * @param start
3550 * the starting file
3551 * @param maxDepth
3552 * the maximum number of directory levels to visit
3553 * @param options
3554 * options to configure the traversal
3555 *
3556 * @return the {@link Stream} of {@link Path}
3557 *
3558 * @throws IllegalArgumentException
3559 * if the {@code maxDepth} parameter is negative
3560 * @throws SecurityException
3561 * If the security manager denies access to the starting file.
3562 * In the case of the default provider, the {@link
3563 * SecurityManager#checkRead(String) checkRead} method is invoked
3564 * to check read access to the directory.
3565 * @throws IOException
3566 * if an I/O error is thrown when accessing the starting file.
3567 * @since 1.8
3568 */
3569 public static Stream<Path> walk(Path start,
3570 int maxDepth,
3571 FileVisitOption... options)
3572 throws IOException
3573 {
3574 FileTreeIterator iterator = new FileTreeIterator(start, maxDepth, options);
3575 try {
3576 return StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, Spliterator.DISTINCT), false)
3577 .onClose(iterator::close)
3578 .map(entry -> entry.file());
3579 } catch (Error|RuntimeException e) {
3580 iterator.close();
3581 throw e;
3582 }
3583 }
3584
3585 /**
3586 * Return a {@code Stream} that is lazily populated with {@code
3587 * Path} by walking the file tree rooted at a given starting file. The
3588 * file tree is traversed <em>depth-first</em>, the elements in the stream
3589 * are {@link Path} objects that are obtained as if by {@link
3590 * Path#resolve(Path) resolving} the relative path against {@code start}.
3591 *
3592 * <p> This method works as if invoking it were equivalent to evaluating the
3593 * expression:
3594 * <blockquote><pre>
3595 * walk(start, Integer.MAX_VALUE, options)
3596 * </pre></blockquote>
3597 * In other words, it visits all levels of the file tree.
3598 *
3599 * <p> The returned stream encapsulates one or more {@link DirectoryStream}s.
3600 * If timely disposal of file system resources is required, the
3601 * {@code try}-with-resources construct should be used to ensure that the
3602 * stream's {@link Stream#close close} method is invoked after the stream
3603 * operations are completed. Operating on a closed stream will result in an
3604 * {@link java.lang.IllegalStateException}.
3605 *
3606 * @param start
3607 * the starting file
3608 * @param options
3609 * options to configure the traversal
3610 *
3611 * @return the {@link Stream} of {@link Path}
3612 *
3613 * @throws SecurityException
3614 * If the security manager denies access to the starting file.
3615 * In the case of the default provider, the {@link
3616 * SecurityManager#checkRead(String) checkRead} method is invoked
3617 * to check read access to the directory.
3618 * @throws IOException
3619 * if an I/O error is thrown when accessing the starting file.
3620 *
3621 * @see #walk(Path, int, FileVisitOption...)
3622 * @since 1.8
3623 */
3624 public static Stream<Path> walk(Path start, FileVisitOption... options) throws IOException {
3625 return walk(start, Integer.MAX_VALUE, options);
3626 }
3627
3628 /**
3629 * Return a {@code Stream} that is lazily populated with {@code
3630 * Path} by searching for files in a file tree rooted at a given starting
3631 * file.
3632 *
3633 * <p> This method walks the file tree in exactly the manner specified by
3634 * the {@link #walk walk} method. For each file encountered, the given
3635 * {@link BiPredicate} is invoked with its {@link Path} and {@link
3636 * BasicFileAttributes}. The {@code Path} object is obtained as if by
3637 * {@link Path#resolve(Path) resolving} the relative path against {@code
3638 * start} and is only included in the returned {@link Stream} if
3639 * the {@code BiPredicate} returns true. Compare to calling {@link
3640 * java.util.stream.Stream#filter filter} on the {@code Stream}
3641 * returned by {@code walk} method, this method may be more efficient by
3642 * avoiding redundant retrieval of the {@code BasicFileAttributes}.
3643 *
3644 * <p> The returned stream encapsulates one or more {@link DirectoryStream}s.
3645 * If timely disposal of file system resources is required, the
3646 * {@code try}-with-resources construct should be used to ensure that the
3647 * stream's {@link Stream#close close} method is invoked after the stream
3648 * operations are completed. Operating on a closed stream will result in an
3649 * {@link java.lang.IllegalStateException}.
3650 *
3651 * <p> If an {@link IOException} is thrown when accessing the directory
3652 * after returned from this method, it is wrapped in an {@link
3653 * UncheckedIOException} which will be thrown from the method that caused
3654 * the access to take place.
3655 *
3656 * @param start
3657 * the starting file
3658 * @param maxDepth
3659 * the maximum number of directory levels to search
3660 * @param matcher
3661 * the function used to decide whether a file should be included
3662 * in the returned stream
3663 * @param options
3664 * options to configure the traversal
3665 *
3666 * @return the {@link Stream} of {@link Path}
3667 *
3668 * @throws IllegalArgumentException
3669 * if the {@code maxDepth} parameter is negative
3670 * @throws SecurityException
3671 * If the security manager denies access to the starting file.
3672 * In the case of the default provider, the {@link
3673 * SecurityManager#checkRead(String) checkRead} method is invoked
3674 * to check read access to the directory.
3675 * @throws IOException
3676 * if an I/O error is thrown when accessing the starting file.
3677 *
3678 * @see #walk(Path, int, FileVisitOption...)
3679 * @since 1.8
3680 */
3681 public static Stream<Path> find(Path start,
3682 int maxDepth,
3683 BiPredicate<Path, BasicFileAttributes> matcher,
3684 FileVisitOption... options)
3685 throws IOException
3686 {
3687 FileTreeIterator iterator = new FileTreeIterator(start, maxDepth, options);
3688 try {
3689 return StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, Spliterator.DISTINCT), false)
3690 .onClose(iterator::close)
3691 .filter(entry -> matcher.test(entry.file(), entry.attributes()))
3692 .map(entry -> entry.file());
3693 } catch (Error|RuntimeException e) {
3694 iterator.close();
3695 throw e;
3696 }
3697 }
3698
3699 /**
3700 * Read all lines from a file as a {@code Stream}. Unlike {@link
3701 * #readAllLines(Path, Charset) readAllLines}, this method does not read
3702 * all lines into a {@code List}, but instead populates lazily as the stream
3703 * is consumed.
3704 *
3705 * <p> Bytes from the file are decoded into characters using the specified
3706 * charset and the same line terminators as specified by {@code
3707 * readAllLines} are supported.
3708 *
3709 * <p> After this method returns, then any subsequent I/O exception that
3710 * occurs while reading from the file or when a malformed or unmappable byte
3711 * sequence is read, is wrapped in an {@link UncheckedIOException} that will
3712 * be thrown from the
3713 * {@link java.util.stream.Stream} method that caused the read to take
3714 * place. In case an {@code IOException} is thrown when closing the file,
3715 * it is also wrapped as an {@code UncheckedIOException}.
3716 *
3717 * <p> The returned stream encapsulates a {@link Reader}. If timely
3718 * disposal of file system resources is required, the try-with-resources
3719 * construct should be used to ensure that the stream's
3720 * {@link Stream#close close} method is invoked after the stream operations
3721 * are completed.
3722 *
3723 *
3724 * @param path
3725 * the path to the file
3726 * @param cs
3727 * the charset to use for decoding
3728 *
3729 * @return the lines from the file as a {@code Stream}
3730 *
3731 * @throws IOException
3732 * if an I/O error occurs opening the file
3733 * @throws SecurityException
3734 * In the case of the default provider, and a security manager is
3735 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3736 * method is invoked to check read access to the file.
3737 *
3738 * @see #readAllLines(Path, Charset)
3739 * @see #newBufferedReader(Path, Charset)
3740 * @see java.io.BufferedReader#lines()
3741 * @since 1.8
3742 */
3743 public static Stream<String> lines(Path path, Charset cs) throws IOException {
3744 BufferedReader br = Files.newBufferedReader(path, cs);
3745 try {
3746 return br.lines().onClose(asUncheckedRunnable(br));
3747 } catch (Error|RuntimeException e) {
3748 try {
3749 br.close();
3750 } catch (IOException ex) {
3751 try {
3752 e.addSuppressed(ex);
3753 } catch (Throwable ignore) {}
3754 }
3755 throw e;
3756 }
3757 }
3758
3759 /**
3760 * Read all lines from a file as a {@code Stream}. Bytes from the file are
3761 * decoded into characters using the {@link StandardCharsets#UTF_8 UTF-8}
3762 * {@link Charset charset}.
3763 *
3764 * <p> This method works as if invoking it were equivalent to evaluating the
3765 * expression:
3766 * <pre>{@code
3767 * Files.lines(path, StandardCharsets.UTF_8)
3768 * }</pre>
3769 *
3770 * @param path
3771 * the path to the file
3772 *
3773 * @return the lines from the file as a {@code Stream}
3774 *
3775 * @throws IOException
3776 * if an I/O error occurs opening the file
3777 * @throws SecurityException
3778 * In the case of the default provider, and a security manager is
3779 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3780 * method is invoked to check read access to the file.
3781 *
3782 * @since 1.8
3783 */
3784 public static Stream<String> lines(Path path) throws IOException {
3785 return lines(path, StandardCharsets.UTF_8);
3786 }
3787 }
3788