1 /*
2 * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.nio.file;
27
28 import java.nio.file.attribute.*;
29 import java.nio.file.spi.FileSystemProvider;
30 import java.nio.file.spi.FileTypeDetector;
31 import java.nio.channels.SeekableByteChannel;
32 import java.io.InputStream;
33 import java.io.OutputStream;
34 import java.io.Reader;
35 import java.io.Writer;
36 import java.io.BufferedReader;
37 import java.io.BufferedWriter;
38 import java.io.InputStreamReader;
39 import java.io.OutputStreamWriter;
40 import java.io.IOException;
41 import java.util.*;
42 import java.security.AccessController;
43 import java.security.PrivilegedAction;
44 import java.nio.charset.Charset;
45 import java.nio.charset.CharsetDecoder;
46 import java.nio.charset.CharsetEncoder;
47
48 /**
49 * This class consists exclusively of static methods that operate on files,
50 * directories, or other types of files.
51 *
52 * <p> In most cases, the methods defined here will delegate to the associated
53 * file system provider to perform the file operations.
54 *
55 * @since 1.7
56 */
57
58 public final class Files {
59 private Files() { }
60
61 /**
62 * Returns the {@code FileSystemProvider} to delegate to.
63 */
64 private static FileSystemProvider provider(Path path) {
65 return path.getFileSystem().provider();
66 }
67
68 // -- File contents --
69
70 /**
71 * Opens a file, returning an input stream to read from the file. The stream
72 * will not be buffered, and is not required to support the {@link
73 * InputStream#mark mark} or {@link InputStream#reset reset} methods. The
74 * stream will be safe for access by multiple concurrent threads. Reading
75 * commences at the beginning of the file. Whether the returned stream is
76 * <i>asynchronously closeable</i> and/or <i>interruptible</i> is highly
77 * file system provider specific and therefore not specified.
78 *
79 * <p> The {@code options} parameter determines how the file is opened.
80 * If no options are present then it is equivalent to opening the file with
81 * the {@link StandardOpenOption#READ READ} option. In addition to the {@code
82 * READ} option, an implementation may also support additional implementation
83 * specific options.
84 *
85 * @param path
86 * the path to the file to open
87 * @param options
88 * options specifying how the file is opened
89 *
90 * @return a new input stream
91 *
92 * @throws IllegalArgumentException
93 * if an invalid combination of options is specified
94 * @throws UnsupportedOperationException
95 * if an unsupported option is specified
96 * @throws IOException
97 * if an I/O error occurs
98 * @throws SecurityException
99 * In the case of the default provider, and a security manager is
100 * installed, the {@link SecurityManager#checkRead(String) checkRead}
101 * method is invoked to check read access to the file.
102 */
103 public static InputStream newInputStream(Path path, OpenOption... options)
104 throws IOException
105 {
106 return provider(path).newInputStream(path, options);
107 }
108
109 /**
110 * Opens or creates a file, returning an output stream that may be used to
111 * write bytes to the file. The resulting stream will not be buffered. The
112 * stream will be safe for access by multiple concurrent threads. Whether
113 * the returned stream is <i>asynchronously closeable</i> and/or
114 * <i>interruptible</i> is highly file system provider specific and
115 * therefore not specified.
116 *
117 * <p> This method opens or creates a file in exactly the manner specified
118 * by the {@link #newByteChannel(Path,Set,FileAttribute[]) newByteChannel}
119 * method with the exception that the {@link StandardOpenOption#READ READ}
120 * option may not be present in the array of options. If no options are
121 * present then this method works as if the {@link StandardOpenOption#CREATE
122 * CREATE}, {@link StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING},
123 * and {@link StandardOpenOption#WRITE WRITE} options are present. In other
124 * words, it opens the file for writing, creating the file if it doesn't
125 * exist, or initially truncating an existing {@link #isRegularFile
126 * regular-file} to a size of {@code 0} if it exists.
127 *
128 * <p> <b>Usage Examples:</b>
129 * <pre>
130 * Path path = ...
131 *
132 * // truncate and overwrite an existing file, or create the file if
133 * // it doesn't initially exist
134 * OutputStream out = Files.newOutputStream(path);
135 *
136 * // append to an existing file, fail if the file does not exist
137 * out = Files.newOutputStream(path, APPEND);
138 *
139 * // append to an existing file, create file if it doesn't initially exist
140 * out = Files.newOutputStream(path, CREATE, APPEND);
141 *
142 * // always create new file, failing if it already exists
143 * out = Files.newOutputStream(path, CREATE_NEW);
144 * </pre>
145 *
146 * @param path
147 * the path to the file to open or create
148 * @param options
149 * options specifying how the file is opened
150 *
151 * @return a new output stream
152 *
153 * @throws IllegalArgumentException
154 * if {@code options} contains an invalid combination of options
155 * @throws UnsupportedOperationException
156 * if an unsupported option is specified
157 * @throws IOException
158 * if an I/O error occurs
159 * @throws SecurityException
160 * In the case of the default provider, and a security manager is
161 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
162 * method is invoked to check write access to the file. The {@link
163 * SecurityManager#checkDelete(String) checkDelete} method is
164 * invoked to check delete access if the file is opened with the
165 * {@code DELETE_ON_CLOSE} option.
166 */
167 public static OutputStream newOutputStream(Path path, OpenOption... options)
168 throws IOException
169 {
170 return provider(path).newOutputStream(path, options);
171 }
172
173 /**
174 * Opens or creates a file, returning a seekable byte channel to access the
175 * file.
176 *
177 * <p> The {@code options} parameter determines how the file is opened.
178 * The {@link StandardOpenOption#READ READ} and {@link
179 * StandardOpenOption#WRITE WRITE} options determine if the file should be
180 * opened for reading and/or writing. If neither option (or the {@link
181 * StandardOpenOption#APPEND APPEND} option) is present then the file is
182 * opened for reading. By default reading or writing commence at the
183 * beginning of the file.
184 *
185 * <p> In the addition to {@code READ} and {@code WRITE}, the following
186 * options may be present:
187 *
188 * <table border=1 cellpadding=5 summary="">
189 * <tr> <th>Option</th> <th>Description</th> </tr>
190 * <tr>
191 * <td> {@link StandardOpenOption#APPEND APPEND} </td>
192 * <td> If this option is present then the file is opened for writing and
193 * each invocation of the channel's {@code write} method first advances
194 * the position to the end of the file and then writes the requested
195 * data. Whether the advancement of the position and the writing of the
196 * data are done in a single atomic operation is system-dependent and
197 * therefore unspecified. This option may not be used in conjunction
198 * with the {@code READ} or {@code TRUNCATE_EXISTING} options. </td>
199 * </tr>
200 * <tr>
201 * <td> {@link StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING} </td>
202 * <td> If this option is present then the existing file is truncated to
203 * a size of 0 bytes. This option is ignored when the file is opened only
204 * for reading. </td>
205 * </tr>
206 * <tr>
207 * <td> {@link StandardOpenOption#CREATE_NEW CREATE_NEW} </td>
208 * <td> If this option is present then a new file is created, failing if
209 * the file already exists or is a symbolic link. When creating a file the
210 * check for the existence of the file and the creation of the file if it
211 * does not exist is atomic with respect to other file system operations.
212 * This option is ignored when the file is opened only for reading. </td>
213 * </tr>
214 * <tr>
215 * <td > {@link StandardOpenOption#CREATE CREATE} </td>
216 * <td> If this option is present then an existing file is opened if it
217 * exists, otherwise a new file is created. This option is ignored if the
218 * {@code CREATE_NEW} option is also present or the file is opened only
219 * for reading. </td>
220 * </tr>
221 * <tr>
222 * <td > {@link StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE} </td>
223 * <td> When this option is present then the implementation makes a
224 * <em>best effort</em> attempt to delete the file when closed by the
225 * {@link SeekableByteChannel#close close} method. If the {@code close}
226 * method is not invoked then a <em>best effort</em> attempt is made to
227 * delete the file when the Java virtual machine terminates. </td>
228 * </tr>
229 * <tr>
230 * <td>{@link StandardOpenOption#SPARSE SPARSE} </td>
231 * <td> When creating a new file this option is a <em>hint</em> that the
232 * new file will be sparse. This option is ignored when not creating
233 * a new file. </td>
234 * </tr>
235 * <tr>
236 * <td> {@link StandardOpenOption#SYNC SYNC} </td>
237 * <td> Requires that every update to the file's content or metadata be
238 * written synchronously to the underlying storage device. (see <a
239 * href="package-summary.html#integrity"> Synchronized I/O file
240 * integrity</a>). </td>
241 * <tr>
242 * <tr>
243 * <td> {@link StandardOpenOption#DSYNC DSYNC} </td>
244 * <td> Requires that every update to the file's content be written
245 * synchronously to the underlying storage device. (see <a
246 * href="package-summary.html#integrity"> Synchronized I/O file
247 * integrity</a>). </td>
248 * </tr>
249 * </table>
250 *
251 * <p> An implementation may also support additional implementation specific
252 * options.
253 *
254 * <p> The {@code attrs} parameter is optional {@link FileAttribute
255 * file-attributes} to set atomically when a new file is created.
256 *
257 * <p> In the case of the default provider, the returned seekable byte channel
258 * is a {@link java.nio.channels.FileChannel}.
259 *
260 * <p> <b>Usage Examples:</b>
261 * <pre>
262 * Path path = ...
263 *
264 * // open file for reading
265 * ReadableByteChannel rbc = Files.newByteChannel(path, EnumSet.of(READ)));
266 *
267 * // open file for writing to the end of an existing file, creating
268 * // the file if it doesn't already exist
269 * WritableByteChannel wbc = Files.newByteChannel(path, EnumSet.of(CREATE,APPEND));
270 *
271 * // create file with initial permissions, opening it for both reading and writing
272 * {@code FileAttribute<Set<PosixFilePermission>> perms = ...}
273 * SeekableByteChannel sbc = Files.newByteChannel(path, EnumSet.of(CREATE_NEW,READ,WRITE), perms);
274 * </pre>
275 *
276 * @param path
277 * the path to the file to open or create
278 * @param options
279 * options specifying how the file is opened
280 * @param attrs
281 * an optional list of file attributes to set atomically when
282 * creating the file
283 *
284 * @return a new seekable byte channel
285 *
286 * @throws IllegalArgumentException
287 * if the set contains an invalid combination of options
288 * @throws UnsupportedOperationException
289 * if an unsupported open option is specified or the array contains
290 * attributes that cannot be set atomically when creating the file
291 * @throws FileAlreadyExistsException
292 * if a file of that name already exists and the {@link
293 * StandardOpenOption#CREATE_NEW CREATE_NEW} option is specified
294 * <i>(optional specific exception)</i>
295 * @throws IOException
296 * if an I/O error occurs
297 * @throws SecurityException
298 * In the case of the default provider, and a security manager is
299 * installed, the {@link SecurityManager#checkRead(String) checkRead}
300 * method is invoked to check read access to the path if the file is
301 * opened for reading. The {@link SecurityManager#checkWrite(String)
302 * checkWrite} method is invoked to check write access to the path
303 * if the file is opened for writing. The {@link
304 * SecurityManager#checkDelete(String) checkDelete} method is
305 * invoked to check delete access if the file is opened with the
306 * {@code DELETE_ON_CLOSE} option.
307 *
308 * @see java.nio.channels.FileChannel#open(Path,Set,FileAttribute[])
309 */
310 public static SeekableByteChannel newByteChannel(Path path,
311 Set<? extends OpenOption> options,
312 FileAttribute<?>... attrs)
313 throws IOException
314 {
315 return provider(path).newByteChannel(path, options, attrs);
316 }
317
318 /**
319 * Opens or creates a file, returning a seekable byte channel to access the
320 * file.
321 *
322 * <p> This method opens or creates a file in exactly the manner specified
323 * by the {@link #newByteChannel(Path,Set,FileAttribute[]) newByteChannel}
324 * method.
325 *
326 * @param path
327 * the path to the file to open or create
328 * @param options
329 * options specifying how the file is opened
330 *
331 * @return a new seekable byte channel
332 *
333 * @throws IllegalArgumentException
334 * if the set contains an invalid combination of options
335 * @throws UnsupportedOperationException
336 * if an unsupported open option is specified
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,OpenOption[])
355 */
356 public static SeekableByteChannel newByteChannel(Path path, OpenOption... options)
357 throws IOException
358 {
359 Set<OpenOption> set = new HashSet<OpenOption>(options.length);
360 Collections.addAll(set, options);
361 return newByteChannel(path, set);
362 }
363
364 // -- Directories --
365
366 private static class AcceptAllFilter
367 implements DirectoryStream.Filter<Path>
368 {
369 private AcceptAllFilter() { }
370
371 @Override
372 public boolean accept(Path entry) { return true; }
373
374 static final AcceptAllFilter FILTER = new AcceptAllFilter();
375 }
376
377 /**
378 * Opens a directory, returning a {@link DirectoryStream} to iterate over
379 * all entries in the directory. The elements returned by the directory
380 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
381 * Path}, each one representing an entry in the directory. The {@code Path}
382 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
383 * name of the directory entry against {@code dir}.
384 *
385 * <p> When not using the try-with-resources construct, then directory
386 * stream's {@code close} method should be invoked after iteration is
387 * completed so as to free any resources held for the open directory.
388 *
389 * <p> When an implementation supports operations on entries in the
390 * directory that execute in a race-free manner then the returned directory
391 * stream is a {@link SecureDirectoryStream}.
392 *
393 * @param dir
394 * the path to the directory
395 *
396 * @return a new and open {@code DirectoryStream} object
397 *
398 * @throws NotDirectoryException
399 * if the file could not otherwise be opened because it is not
400 * a directory <i>(optional specific exception)</i>
401 * @throws IOException
402 * if an I/O error occurs
403 * @throws SecurityException
404 * In the case of the default provider, and a security manager is
405 * installed, the {@link SecurityManager#checkRead(String) checkRead}
406 * method is invoked to check read access to the directory.
407 */
408 public static DirectoryStream<Path> newDirectoryStream(Path dir)
409 throws IOException
410 {
411 return provider(dir).newDirectoryStream(dir, AcceptAllFilter.FILTER);
412 }
413
414 /**
415 * Opens a directory, returning a {@link DirectoryStream} to iterate over
416 * the entries in the directory. The elements returned by the directory
417 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
418 * Path}, each one representing an entry in the directory. The {@code Path}
419 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
420 * name of the directory entry against {@code dir}. The entries returned by
421 * the iterator are filtered by matching the {@code String} representation
422 * of their file names against the given <em>globbing</em> pattern.
423 *
424 * <p> For example, suppose we want to iterate over the files ending with
425 * ".java" in a directory:
426 * <pre>
427 * Path dir = ...
428 * try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, "*.java")) {
429 * :
430 * }
431 * </pre>
432 *
433 * <p> The globbing pattern is specified by the {@link
434 * FileSystem#getPathMatcher getPathMatcher} method.
435 *
436 * <p> When not using the try-with-resources construct, then directory
437 * stream's {@code close} method should be invoked after iteration is
438 * completed so as to free any resources held for the open directory.
439 *
440 * <p> When an implementation supports operations on entries in the
441 * directory that execute in a race-free manner then the returned directory
442 * stream is a {@link SecureDirectoryStream}.
443 *
444 * @param dir
445 * the path to the directory
446 * @param glob
447 * the glob pattern
448 *
449 * @return a new and open {@code DirectoryStream} object
450 *
451 * @throws java.util.regex.PatternSyntaxException
452 * if the pattern is invalid
453 * @throws NotDirectoryException
454 * if the file could not otherwise be opened because it is not
455 * a directory <i>(optional specific exception)</i>
456 * @throws IOException
457 * if an I/O error occurs
458 * @throws SecurityException
459 * In the case of the default provider, and a security manager is
460 * installed, the {@link SecurityManager#checkRead(String) checkRead}
461 * method is invoked to check read access to the directory.
462 */
463 public static DirectoryStream<Path> newDirectoryStream(Path dir, String glob)
464 throws IOException
465 {
466 // avoid creating a matcher if all entries are required.
467 if (glob.equals("*"))
468 return newDirectoryStream(dir);
469
470 // create a matcher and return a filter that uses it.
471 FileSystem fs = dir.getFileSystem();
472 final PathMatcher matcher = fs.getPathMatcher("glob:" + glob);
473 DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
474 @Override
475 public boolean accept(Path entry) {
476 return matcher.matches(entry.getFileName());
477 }
478 };
479 return fs.provider().newDirectoryStream(dir, filter);
480 }
481
482 /**
483 * Opens a directory, returning a {@link DirectoryStream} to iterate over
484 * the entries in the directory. The elements returned by the directory
485 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
486 * Path}, each one representing an entry in the directory. The {@code Path}
487 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
488 * name of the directory entry against {@code dir}. The entries returned by
489 * the iterator are filtered by the given {@link DirectoryStream.Filter
490 * filter}.
491 *
492 * <p> When not using the try-with-resources construct, then directory
493 * stream's {@code close} method should be invoked after iteration is
494 * completed so as to free any resources held for the open directory.
495 *
496 * <p> Where the filter terminates due to an uncaught error or runtime
497 * exception then it is propagated to the {@link Iterator#hasNext()
498 * hasNext} or {@link Iterator#next() next} method. Where an {@code
499 * IOException} is thrown, it results in the {@code hasNext} or {@code
500 * next} method throwing a {@link DirectoryIteratorException} with the
501 * {@code IOException} as the cause.
502 *
503 * <p> When an implementation supports operations on entries in the
504 * directory that execute in a race-free manner then the returned directory
505 * stream is a {@link SecureDirectoryStream}.
506 *
507 * <p> <b>Usage Example:</b>
508 * Suppose we want to iterate over the files in a directory that are
509 * larger than 8K.
510 * <pre>
511 * DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
512 * public boolean accept(Path file) throws IOException {
513 * return (Files.size(file) > 8192L);
514 * }
515 * };
516 * Path dir = ...
517 * try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, filter)) {
518 * :
519 * }
520 * </pre>
521 *
522 * @param dir
523 * the path to the directory
524 * @param filter
525 * the directory stream filter
526 *
527 * @return a new and open {@code DirectoryStream} object
528 *
529 * @throws NotDirectoryException
530 * if the file could not otherwise be opened because it is not
531 * a directory <i>(optional specific exception)</i>
532 * @throws IOException
533 * if an I/O error occurs
534 * @throws SecurityException
535 * In the case of the default provider, and a security manager is
536 * installed, the {@link SecurityManager#checkRead(String) checkRead}
537 * method is invoked to check read access to the directory.
538 */
539 public static DirectoryStream<Path> newDirectoryStream(Path dir,
540 DirectoryStream.Filter<? super Path> filter)
541 throws IOException
542 {
543 return provider(dir).newDirectoryStream(dir, filter);
544 }
545
546 // -- Creation and deletion --
547
548 /**
549 * Creates a new and empty file, failing if the file already exists. The
550 * check for the existence of the file and the creation of the new file if
551 * it does not exist are a single operation that is atomic with respect to
552 * all other filesystem activities that might affect the directory.
553 *
554 * <p> The {@code attrs} parameter is optional {@link FileAttribute
555 * file-attributes} to set atomically when creating the file. Each attribute
556 * is identified by its {@link FileAttribute#name name}. If more than one
557 * attribute of the same name is included in the array then all but the last
558 * occurrence is ignored.
559 *
560 * @param path
561 * the path to the file to create
562 * @param attrs
563 * an optional list of file attributes to set atomically when
564 * creating the file
565 *
566 * @return the file
567 *
568 * @throws UnsupportedOperationException
569 * if the array contains an attribute that cannot be set atomically
570 * when creating the file
571 * @throws FileAlreadyExistsException
572 * if a file of that name already exists
573 * <i>(optional specific exception)</i>
574 * @throws IOException
575 * if an I/O error occurs or the parent directory does not exist
576 * @throws SecurityException
577 * In the case of the default provider, and a security manager is
578 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
579 * method is invoked to check write access to the new file.
580 */
581 public static Path createFile(Path path, FileAttribute<?>... attrs)
582 throws IOException
583 {
584 EnumSet<StandardOpenOption> options =
585 EnumSet.<StandardOpenOption>of(StandardOpenOption.CREATE_NEW, StandardOpenOption.WRITE);
586 newByteChannel(path, options, attrs).close();
587 return path;
588 }
589
590 /**
591 * Creates a new directory. The check for the existence of the file and the
592 * creation of the directory if it does not exist are a single operation
593 * that is atomic with respect to all other filesystem activities that might
594 * affect the directory. The {@link #createDirectories createDirectories}
595 * method should be used where it is required to create all nonexistent
596 * parent directories first.
597 *
598 * <p> The {@code attrs} parameter is optional {@link FileAttribute
599 * file-attributes} to set atomically when creating the directory. Each
600 * attribute is identified by its {@link FileAttribute#name name}. If more
601 * than one attribute of the same name is included in the array then all but
602 * the last occurrence is ignored.
603 *
604 * @param dir
605 * the directory to create
606 * @param attrs
607 * an optional list of file attributes to set atomically when
608 * creating the directory
609 *
610 * @return the directory
611 *
612 * @throws UnsupportedOperationException
613 * if the array contains an attribute that cannot be set atomically
614 * when creating the directory
615 * @throws FileAlreadyExistsException
616 * if a directory could not otherwise be created because a file of
617 * that name already exists <i>(optional specific exception)</i>
618 * @throws IOException
619 * if an I/O error occurs or the parent directory does not exist
620 * @throws SecurityException
621 * In the case of the default provider, and a security manager is
622 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
623 * method is invoked to check write access to the new directory.
624 */
625 public static Path createDirectory(Path dir, FileAttribute<?>... attrs)
626 throws IOException
627 {
628 provider(dir).createDirectory(dir, attrs);
629 return dir;
630 }
631
632 /**
633 * Creates a directory by creating all nonexistent parent directories first.
634 * Unlike the {@link #createDirectory createDirectory} method, an exception
635 * is not thrown if the directory could not be created because it already
636 * exists.
637 *
638 * <p> The {@code attrs} parameter is optional {@link FileAttribute
639 * file-attributes} to set atomically when creating the nonexistent
640 * directories. Each file attribute is identified by its {@link
641 * FileAttribute#name name}. If more than one attribute of the same name is
642 * included in the array then all but the last occurrence is ignored.
643 *
644 * <p> If this method fails, then it may do so after creating some, but not
645 * all, of the parent directories.
646 *
647 * @param dir
648 * the directory to create
649 *
650 * @param attrs
651 * an optional list of file attributes to set atomically when
652 * creating the directory
653 *
654 * @return the directory
655 *
656 * @throws UnsupportedOperationException
657 * if the array contains an attribute that cannot be set atomically
658 * when creating the directory
659 * @throws FileAlreadyExistsException
660 * if {@code dir} exists but is not a directory <i>(optional specific
661 * exception)</i>
662 * @throws IOException
663 * if an I/O error occurs
664 * @throws SecurityException
665 * in the case of the default provider, and a security manager is
666 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
667 * method is invoked prior to attempting to create a directory and
668 * its {@link SecurityManager#checkRead(String) checkRead} is
669 * invoked for each parent directory that is checked. If {@code
670 * dir} is not an absolute path then its {@link Path#toAbsolutePath
671 * toAbsolutePath} may need to be invoked to get its absolute path.
672 * This may invoke the security manager's {@link
673 * SecurityManager#checkPropertyAccess(String) checkPropertyAccess}
674 * method to check access to the system property {@code user.dir}
675 */
676 public static Path createDirectories(Path dir, FileAttribute<?>... attrs)
677 throws IOException
678 {
679 // attempt to create the directory
680 try {
681 createAndCheckIsDirectory(dir, attrs);
682 return dir;
683 } catch (FileAlreadyExistsException x) {
684 // file exists and is not a directory
685 throw x;
686 } catch (IOException x) {
687 // parent may not exist or other reason
688 }
689 SecurityException se = null;
690 try {
691 dir = dir.toAbsolutePath();
692 } catch (SecurityException x) {
693 // don't have permission to get absolute path
694 se = x;
695 }
696 // find a decendent that exists
697 Path parent = dir.getParent();
698 while (parent != null) {
699 try {
700 provider(parent).checkAccess(parent);
701 break;
702 } catch (NoSuchFileException x) {
703 // does not exist
704 }
705 parent = parent.getParent();
706 }
707 if (parent == null) {
708 // unable to find existing parent
709 if (se != null)
710 throw se;
711 throw new IOException("Root directory does not exist");
712 }
713
714 // create directories
715 Path child = parent;
716 for (Path name: parent.relativize(dir)) {
717 child = child.resolve(name);
718 createAndCheckIsDirectory(child, attrs);
719 }
720 return dir;
721 }
722
723 /**
724 * Used by createDirectories to attempt to create a directory. A no-op
725 * if the directory already exists.
726 */
727 private static void createAndCheckIsDirectory(Path dir,
728 FileAttribute<?>... attrs)
729 throws IOException
730 {
731 try {
732 createDirectory(dir, attrs);
733 } catch (FileAlreadyExistsException x) {
734 if (!isDirectory(dir, LinkOption.NOFOLLOW_LINKS))
735 throw x;
736 }
737 }
738
739 /**
740 * Creates a new empty file in the specified directory, using the given
741 * prefix and suffix strings to generate its name. The resulting
742 * {@code Path} is associated with the same {@code FileSystem} as the given
743 * directory.
744 *
745 * <p> The details as to how the name of the file is constructed is
746 * implementation dependent and therefore not specified. Where possible
747 * the {@code prefix} and {@code suffix} are used to construct candidate
748 * names in the same manner as the {@link
749 * java.io.File#createTempFile(String,String,File)} method.
750 *
751 * <p> As with the {@code File.createTempFile} methods, this method is only
752 * part of a temporary-file facility. Where used as a <em>work files</em>,
753 * the resulting file may be opened using the {@link
754 * StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE} option so that the
755 * file is deleted when the appropriate {@code close} method is invoked.
756 * Alternatively, a {@link Runtime#addShutdownHook shutdown-hook}, or the
757 * {@link java.io.File#deleteOnExit} mechanism may be used to delete the
758 * file automatically.
759 *
760 * <p> The {@code attrs} parameter is optional {@link FileAttribute
761 * file-attributes} to set atomically when creating the file. Each attribute
762 * is identified by its {@link FileAttribute#name name}. If more than one
763 * attribute of the same name is included in the array then all but the last
764 * occurrence is ignored. When no file attributes are specified, then the
765 * resulting file may have more restrictive access permissions to files
766 * created by the {@link java.io.File#createTempFile(String,String,File)}
767 * method.
768 *
769 * @param dir
770 * the path to directory in which to create the file
771 * @param prefix
772 * the prefix string to be used in generating the file's name;
773 * may be {@code null}
774 * @param suffix
775 * the suffix string to be used in generating the file's name;
776 * may be {@code null}, in which case "{@code .tmp}" is used
777 * @param attrs
778 * an optional list of file attributes to set atomically when
779 * creating the file
780 *
781 * @return the path to the newly created file that did not exist before
782 * this method was invoked
783 *
784 * @throws IllegalArgumentException
785 * if the prefix or suffix parameters cannot be used to generate
786 * a candidate file name
787 * @throws UnsupportedOperationException
788 * if the array contains an attribute that cannot be set atomically
789 * when creating the directory
790 * @throws IOException
791 * if an I/O error occurs or {@code dir} does not exist
792 * @throws SecurityException
793 * In the case of the default provider, and a security manager is
794 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
795 * method is invoked to check write access to the file.
796 */
797 public static Path createTempFile(Path dir,
798 String prefix,
799 String suffix,
800 FileAttribute<?>... attrs)
801 throws IOException
802 {
803 return TempFileHelper.createTempFile(Objects.requireNonNull(dir),
804 prefix, suffix, attrs);
805 }
806
807 /**
808 * Creates an empty file in the default temporary-file directory, using
809 * the given prefix and suffix to generate its name. The resulting {@code
810 * Path} is associated with the default {@code FileSystem}.
811 *
812 * <p> This method works in exactly the manner specified by the
813 * {@link #createTempFile(Path,String,String,FileAttribute[])} method for
814 * the case that the {@code dir} parameter is the temporary-file directory.
815 *
816 * @param prefix
817 * the prefix string to be used in generating the file's name;
818 * may be {@code null}
819 * @param suffix
820 * the suffix string to be used in generating the file's name;
821 * may be {@code null}, in which case "{@code .tmp}" is used
822 * @param attrs
823 * an optional list of file attributes to set atomically when
824 * creating the file
825 *
826 * @return the path to the newly created file that did not exist before
827 * this method was invoked
828 *
829 * @throws IllegalArgumentException
830 * if the prefix or suffix parameters cannot be used to generate
831 * a candidate file name
832 * @throws UnsupportedOperationException
833 * if the array contains an attribute that cannot be set atomically
834 * when creating the directory
835 * @throws IOException
836 * if an I/O error occurs or the temporary-file directory does not
837 * exist
838 * @throws SecurityException
839 * In the case of the default provider, and a security manager is
840 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
841 * method is invoked to check write access to the file.
842 */
843 public static Path createTempFile(String prefix,
844 String suffix,
845 FileAttribute<?>... attrs)
846 throws IOException
847 {
848 return TempFileHelper.createTempFile(null, prefix, suffix, attrs);
849 }
850
851 /**
852 * Creates a new directory in the specified directory, using the given
853 * prefix to generate its name. The resulting {@code Path} is associated
854 * with the same {@code FileSystem} as the given directory.
855 *
856 * <p> The details as to how the name of the directory is constructed is
857 * implementation dependent and therefore not specified. Where possible
858 * the {@code prefix} is used to construct candidate names.
859 *
860 * <p> As with the {@code createTempFile} methods, this method is only
861 * part of a temporary-file facility. A {@link Runtime#addShutdownHook
862 * shutdown-hook}, or the {@link java.io.File#deleteOnExit} mechanism may be
863 * used to delete the directory automatically.
864 *
865 * <p> The {@code attrs} parameter is optional {@link FileAttribute
866 * file-attributes} to set atomically when creating the directory. Each
867 * attribute is identified by its {@link FileAttribute#name name}. If more
868 * than one attribute of the same name is included in the array then all but
869 * the last occurrence is ignored.
870 *
871 * @param dir
872 * the path to directory in which to create the directory
873 * @param prefix
874 * the prefix string to be used in generating the directory's name;
875 * may be {@code null}
876 * @param attrs
877 * an optional list of file attributes to set atomically when
878 * creating the directory
879 *
880 * @return the path to the newly created directory that did not exist before
881 * this method was invoked
882 *
883 * @throws IllegalArgumentException
884 * if the prefix cannot be used to generate a candidate directory name
885 * @throws UnsupportedOperationException
886 * if the array contains an attribute that cannot be set atomically
887 * when creating the directory
888 * @throws IOException
889 * if an I/O error occurs or {@code dir} does not exist
890 * @throws SecurityException
891 * In the case of the default provider, and a security manager is
892 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
893 * method is invoked to check write access when creating the
894 * directory.
895 */
896 public static Path createTempDirectory(Path dir,
897 String prefix,
898 FileAttribute<?>... attrs)
899 throws IOException
900 {
901 return TempFileHelper.createTempDirectory(Objects.requireNonNull(dir),
902 prefix, attrs);
903 }
904
905 /**
906 * Creates a new directory in the default temporary-file directory, using
907 * the given prefix to generate its name. The resulting {@code Path} is
908 * associated with the default {@code FileSystem}.
909 *
910 * <p> This method works in exactly the manner specified by {@link
911 * #createTempDirectory(Path,String,FileAttribute[])} method for the case
912 * that the {@code dir} parameter is the temporary-file directory.
913 *
914 * @param prefix
915 * the prefix string to be used in generating the directory's name;
916 * may be {@code null}
917 * @param attrs
918 * an optional list of file attributes to set atomically when
919 * creating the directory
920 *
921 * @return the path to the newly created directory that did not exist before
922 * this method was invoked
923 *
924 * @throws IllegalArgumentException
925 * if the prefix cannot be used to generate a candidate directory name
926 * @throws UnsupportedOperationException
927 * if the array contains an attribute that cannot be set atomically
928 * when creating the directory
929 * @throws IOException
930 * if an I/O error occurs or the temporary-file directory does not
931 * exist
932 * @throws SecurityException
933 * In the case of the default provider, and a security manager is
934 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
935 * method is invoked to check write access when creating the
936 * directory.
937 */
938 public static Path createTempDirectory(String prefix,
939 FileAttribute<?>... attrs)
940 throws IOException
941 {
942 return TempFileHelper.createTempDirectory(null, prefix, attrs);
943 }
944
945 /**
946 * Creates a symbolic link to a target <i>(optional operation)</i>.
947 *
948 * <p> The {@code target} parameter is the target of the link. It may be an
949 * {@link Path#isAbsolute absolute} or relative path and may not exist. When
950 * the target is a relative path then file system operations on the resulting
951 * link are relative to the path of the link.
952 *
953 * <p> The {@code attrs} parameter is optional {@link FileAttribute
954 * attributes} to set atomically when creating the link. Each attribute is
955 * identified by its {@link FileAttribute#name name}. If more than one attribute
956 * of the same name is included in the array then all but the last occurrence
957 * is ignored.
958 *
959 * <p> Where symbolic links are supported, but the underlying {@link FileStore}
960 * does not support symbolic links, then this may fail with an {@link
961 * IOException}. Additionally, some operating systems may require that the
962 * Java virtual machine be started with implementation specific privileges to
963 * create symbolic links, in which case this method may throw {@code IOException}.
964 *
965 * @param link
966 * the path of the symbolic link to create
967 * @param target
968 * the target of the symbolic link
969 * @param attrs
970 * the array of attributes to set atomically when creating the
971 * symbolic link
972 *
973 * @return the path to the symbolic link
974 *
975 * @throws UnsupportedOperationException
976 * if the implementation does not support symbolic links or the
977 * array contains an attribute that cannot be set atomically when
978 * creating the symbolic link
979 * @throws FileAlreadyExistsException
980 * if a file with the name already exists <i>(optional specific
981 * exception)</i>
982 * @throws IOException
983 * if an I/O error occurs
984 * @throws SecurityException
985 * In the case of the default provider, and a security manager
986 * is installed, it denies {@link LinkPermission}<tt>("symbolic")</tt>
987 * or its {@link SecurityManager#checkWrite(String) checkWrite}
988 * method denies write access to the path of the symbolic link.
989 */
990 public static Path createSymbolicLink(Path link, Path target,
991 FileAttribute<?>... attrs)
992 throws IOException
993 {
994 provider(link).createSymbolicLink(link, target, attrs);
995 return link;
996 }
997
998 /**
999 * Creates a new link (directory entry) for an existing file <i>(optional
1000 * operation)</i>.
1001 *
1002 * <p> The {@code link} parameter locates the directory entry to create.
1003 * The {@code existing} parameter is the path to an existing file. This
1004 * method creates a new directory entry for the file so that it can be
1005 * accessed using {@code link} as the path. On some file systems this is
1006 * known as creating a "hard link". Whether the file attributes are
1007 * maintained for the file or for each directory entry is file system
1008 * specific and therefore not specified. Typically, a file system requires
1009 * that all links (directory entries) for a file be on the same file system.
1010 * Furthermore, on some platforms, the Java virtual machine may require to
1011 * be started with implementation specific privileges to create hard links
1012 * or to create links to directories.
1013 *
1014 * @param link
1015 * the link (directory entry) to create
1016 * @param existing
1017 * a path to an existing file
1018 *
1019 * @return the path to the link (directory entry)
1020 *
1021 * @throws UnsupportedOperationException
1022 * if the implementation does not support adding an existing file
1023 * to a directory
1024 * @throws FileAlreadyExistsException
1025 * if the entry could not otherwise be created because a file of
1026 * that name already exists <i>(optional specific exception)</i>
1027 * @throws IOException
1028 * if an I/O error occurs
1029 * @throws SecurityException
1030 * In the case of the default provider, and a security manager
1031 * is installed, it denies {@link LinkPermission}<tt>("hard")</tt>
1032 * or its {@link SecurityManager#checkWrite(String) checkWrite}
1033 * method denies write access to either the link or the
1034 * existing file.
1035 */
1036 public static Path createLink(Path link, Path existing) throws IOException {
1037 provider(link).createLink(link, existing);
1038 return link;
1039 }
1040
1041 /**
1042 * Deletes a file.
1043 *
1044 * <p> An implementation may require to examine the file to determine if the
1045 * file is a directory. Consequently this method may not be atomic with respect
1046 * to other file system operations. If the file is a symbolic link then the
1047 * symbolic link itself, not the final target of the link, is deleted.
1048 *
1049 * <p> If the file is a directory then the directory must be empty. In some
1050 * implementations a directory has entries for special files or links that
1051 * are created when the directory is created. In such implementations a
1052 * directory is considered empty when only the special entries exist.
1053 * This method can be used with the {@link #walkFileTree walkFileTree}
1054 * method to delete a directory and all entries in the directory, or an
1055 * entire <i>file-tree</i> where required.
1056 *
1057 * <p> On some operating systems it may not be possible to remove a file when
1058 * it is open and in use by this Java virtual machine or other programs.
1059 *
1060 * @param path
1061 * the path to the file to delete
1062 *
1063 * @throws NoSuchFileException
1064 * if the file does not exist <i>(optional specific exception)</i>
1065 * @throws DirectoryNotEmptyException
1066 * if the file is a directory and could not otherwise be deleted
1067 * because the directory is not empty <i>(optional specific
1068 * exception)</i>
1069 * @throws IOException
1070 * if an I/O error occurs
1071 * @throws SecurityException
1072 * In the case of the default provider, and a security manager is
1073 * installed, the {@link SecurityManager#checkDelete(String)} method
1074 * is invoked to check delete access to the file
1075 */
1076 public static void delete(Path path) throws IOException {
1077 provider(path).delete(path);
1078 }
1079
1080 /**
1081 * Deletes a file if it exists.
1082 *
1083 * <p> As with the {@link #delete(Path) delete(Path)} method, an
1084 * implementation may need to examine the file to determine if the file is a
1085 * directory. Consequently this method may not be atomic with respect to
1086 * other file system operations. If the file is a symbolic link, then the
1087 * symbolic link itself, not the final target of the link, is deleted.
1088 *
1089 * <p> If the file is a directory then the directory must be empty. In some
1090 * implementations a directory has entries for special files or links that
1091 * are created when the directory is created. In such implementations a
1092 * directory is considered empty when only the special entries exist.
1093 *
1094 * <p> On some operating systems it may not be possible to remove a file when
1095 * it is open and in use by this Java virtual machine or other programs.
1096 *
1097 * @param path
1098 * the path to the file to delete
1099 *
1100 * @return {@code true} if the file was deleted by this method; {@code
1101 * false} if the file could not be deleted because it did not
1102 * exist
1103 *
1104 * @throws DirectoryNotEmptyException
1105 * if the file is a directory and could not otherwise be deleted
1106 * because the directory is not empty <i>(optional specific
1107 * exception)</i>
1108 * @throws IOException
1109 * if an I/O error occurs
1110 * @throws SecurityException
1111 * In the case of the default provider, and a security manager is
1112 * installed, the {@link SecurityManager#checkDelete(String)} method
1113 * is invoked to check delete access to the file.
1114 */
1115 public static boolean deleteIfExists(Path path) throws IOException {
1116 return provider(path).deleteIfExists(path);
1117 }
1118
1119 // -- Copying and moving files --
1120
1121 /**
1122 * Copy a file to a target file.
1123 *
1124 * <p> This method copies a file to the target file with the {@code
1125 * options} parameter specifying how the copy is performed. By default, the
1126 * copy fails if the target file already exists or is a symbolic link,
1127 * except if the source and target are the {@link #isSameFile same} file, in
1128 * which case the method completes without copying the file. File attributes
1129 * are not required to be copied to the target file. If symbolic links are
1130 * supported, and the file is a symbolic link, then the final target of the
1131 * link is copied. If the file is a directory then it creates an empty
1132 * directory in the target location (entries in the directory are not
1133 * copied). This method can be used with the {@link #walkFileTree
1134 * walkFileTree} method to copy a directory and all entries in the directory,
1135 * or an entire <i>file-tree</i> where required.
1136 *
1137 * <p> The {@code options} parameter may include any of the following:
1138 *
1139 * <table border=1 cellpadding=5 summary="">
1140 * <tr> <th>Option</th> <th>Description</th> </tr>
1141 * <tr>
1142 * <td> {@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING} </td>
1143 * <td> If the target file exists, then the target file is replaced if it
1144 * is not a non-empty directory. If the target file exists and is a
1145 * symbolic link, then the symbolic link itself, not the target of
1146 * the link, is replaced. </td>
1147 * </tr>
1148 * <tr>
1149 * <td> {@link StandardCopyOption#COPY_ATTRIBUTES COPY_ATTRIBUTES} </td>
1150 * <td> Attempts to copy the file attributes associated with this file to
1151 * the target file. The exact file attributes that are copied is platform
1152 * and file system dependent and therefore unspecified. Minimally, the
1153 * {@link BasicFileAttributes#lastModifiedTime last-modified-time} is
1154 * copied to the target file if supported by both the source and target
1155 * file store. Copying of file timestamps may result in precision
1156 * loss. </td>
1157 * </tr>
1158 * <tr>
1159 * <td> {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} </td>
1160 * <td> Symbolic links are not followed. If the file is a symbolic link,
1161 * then the symbolic link itself, not the target of the link, is copied.
1162 * It is implementation specific if file attributes can be copied to the
1163 * new link. In other words, the {@code COPY_ATTRIBUTES} option may be
1164 * ignored when copying a symbolic link. </td>
1165 * </tr>
1166 * </table>
1167 *
1168 * <p> An implementation of this interface may support additional
1169 * implementation specific options.
1170 *
1171 * <p> Copying a file is not an atomic operation. If an {@link IOException}
1172 * is thrown then it possible that the target file is incomplete or some of
1173 * its file attributes have not been copied from the source file. When the
1174 * {@code REPLACE_EXISTING} option is specified and the target file exists,
1175 * then the target file is replaced. The check for the existence of the file
1176 * and the creation of the new file may not be atomic with respect to other
1177 * file system activities.
1178 *
1179 * <p> <b>Usage Example:</b>
1180 * Suppose we want to copy a file into a directory, giving it the same file
1181 * name as the source file:
1182 * <pre>
1183 * Path source = ...
1184 * Path newdir = ...
1185 * Files.copy(source, newdir.resolve(source.getFileName());
1186 * </pre>
1187 *
1188 * @param source
1189 * the path to the file to copy
1190 * @param target
1191 * the path to the target file (may be associated with a different
1192 * provider to the source path)
1193 * @param options
1194 * options specifying how the copy should be done
1195 *
1196 * @return the path to the target file
1197 *
1198 * @throws UnsupportedOperationException
1199 * if the array contains a copy option that is not supported
1200 * @throws FileAlreadyExistsException
1201 * if the target file exists but cannot be replaced because the
1202 * {@code REPLACE_EXISTING} option is not specified <i>(optional
1203 * specific exception)</i>
1204 * @throws DirectoryNotEmptyException
1205 * the {@code REPLACE_EXISTING} option is specified but the file
1206 * cannot be replaced because it is a non-empty directory
1207 * <i>(optional specific exception)</i>
1208 * @throws IOException
1209 * if an I/O error occurs
1210 * @throws SecurityException
1211 * In the case of the default provider, and a security manager is
1212 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1213 * method is invoked to check read access to the source file, the
1214 * {@link SecurityManager#checkWrite(String) checkWrite} is invoked
1215 * to check write access to the target file. If a symbolic link is
1216 * copied the security manager is invoked to check {@link
1217 * LinkPermission}{@code ("symbolic")}.
1218 */
1219 public static Path copy(Path source, Path target, CopyOption... options)
1220 throws IOException
1221 {
1222 FileSystemProvider provider = provider(source);
1223 if (provider(target) == provider) {
1224 // same provider
1225 provider.copy(source, target, options);
1226 } else {
1227 // different providers
1228 CopyMoveHelper.copyToForeignTarget(source, target, options);
1229 }
1230 return target;
1231 }
1232
1233 /**
1234 * Move or rename a file to a target file.
1235 *
1236 * <p> By default, this method attempts to move the file to the target
1237 * file, failing if the target file exists except if the source and
1238 * target are the {@link #isSameFile same} file, in which case this method
1239 * has no effect. If the file is a symbolic link then the symbolic link
1240 * itself, not the target of the link, is moved. This method may be
1241 * invoked to move an empty directory. In some implementations a directory
1242 * has entries for special files or links that are created when the
1243 * directory is created. In such implementations a directory is considered
1244 * empty when only the special entries exist. When invoked to move a
1245 * directory that is not empty then the directory is moved if it does not
1246 * require moving the entries in the directory. For example, renaming a
1247 * directory on the same {@link FileStore} will usually not require moving
1248 * the entries in the directory. When moving a directory requires that its
1249 * entries be moved then this method fails (by throwing an {@code
1250 * IOException}). To move a <i>file tree</i> may involve copying rather
1251 * than moving directories and this can be done using the {@link
1252 * #copy copy} method in conjunction with the {@link
1253 * #walkFileTree Files.walkFileTree} utility method.
1254 *
1255 * <p> The {@code options} parameter may include any of the following:
1256 *
1257 * <table border=1 cellpadding=5 summary="">
1258 * <tr> <th>Option</th> <th>Description</th> </tr>
1259 * <tr>
1260 * <td> {@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING} </td>
1261 * <td> If the target file exists, then the target file is replaced if it
1262 * is not a non-empty directory. If the target file exists and is a
1263 * symbolic link, then the symbolic link itself, not the target of
1264 * the link, is replaced. </td>
1265 * </tr>
1266 * <tr>
1267 * <td> {@link StandardCopyOption#ATOMIC_MOVE ATOMIC_MOVE} </td>
1268 * <td> The move is performed as an atomic file system operation and all
1269 * other options are ignored. If the target file exists then it is
1270 * implementation specific if the existing file is replaced or this method
1271 * fails by throwing an {@link IOException}. If the move cannot be
1272 * performed as an atomic file system operation then {@link
1273 * AtomicMoveNotSupportedException} is thrown. This can arise, for
1274 * example, when the target location is on a different {@code FileStore}
1275 * and would require that the file be copied, or target location is
1276 * associated with a different provider to this object. </td>
1277 * </table>
1278 *
1279 * <p> An implementation of this interface may support additional
1280 * implementation specific options.
1281 *
1282 * <p> Where the move requires that the file be copied then the {@link
1283 * BasicFileAttributes#lastModifiedTime last-modified-time} is copied to the
1284 * new file. An implementation may also attempt to copy other file
1285 * attributes but is not required to fail if the file attributes cannot be
1286 * copied. When the move is performed as a non-atomic operation, and a {@code
1287 * IOException} is thrown, then the state of the files is not defined. The
1288 * original file and the target file may both exist, the target file may be
1289 * incomplete or some of its file attributes may not been copied from the
1290 * original file.
1291 *
1292 * <p> <b>Usage Examples:</b>
1293 * Suppose we want to rename a file to "newname", keeping the file in the
1294 * same directory:
1295 * <pre>
1296 * Path source = ...
1297 * Files.move(source, source.resolveSibling("newname"));
1298 * </pre>
1299 * Alternatively, suppose we want to move a file to new directory, keeping
1300 * the same file name, and replacing any existing file of that name in the
1301 * directory:
1302 * <pre>
1303 * Path source = ...
1304 * Path newdir = ...
1305 * Files.move(source, newdir.resolve(source.getFileName()), REPLACE_EXISTING);
1306 * </pre>
1307 *
1308 * @param source
1309 * the path to the file to move
1310 * @param target
1311 * the path to the target file (may be associated with a different
1312 * provider to the source path)
1313 * @param options
1314 * options specifying how the move should be done
1315 *
1316 * @return the path to the target file
1317 *
1318 * @throws UnsupportedOperationException
1319 * if the array contains a copy option that is not supported
1320 * @throws FileAlreadyExistsException
1321 * if the target file exists but cannot be replaced because the
1322 * {@code REPLACE_EXISTING} option is not specified <i>(optional
1323 * specific exception)</i>
1324 * @throws DirectoryNotEmptyException
1325 * the {@code REPLACE_EXISTING} option is specified but the file
1326 * cannot be replaced because it is a non-empty directory
1327 * <i>(optional specific exception)</i>
1328 * @throws AtomicMoveNotSupportedException
1329 * if the options array contains the {@code ATOMIC_MOVE} option but
1330 * the file cannot be moved as an atomic file system operation.
1331 * @throws IOException
1332 * if an I/O error occurs
1333 * @throws SecurityException
1334 * In the case of the default provider, and a security manager is
1335 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
1336 * method is invoked to check write access to both the source and
1337 * target file.
1338 */
1339 public static Path move(Path source, Path target, CopyOption... options)
1340 throws IOException
1341 {
1342 FileSystemProvider provider = provider(source);
1343 if (provider(target) == provider) {
1344 // same provider
1345 provider.move(source, target, options);
1346 } else {
1347 // different providers
1348 CopyMoveHelper.moveToForeignTarget(source, target, options);
1349 }
1350 return target;
1351 }
1352
1353 // -- Miscellenous --
1354
1355 /**
1356 * Reads the target of a symbolic link <i>(optional operation)</i>.
1357 *
1358 * <p> If the file system supports <a href="package-summary.html#links">symbolic
1359 * links</a> then this method is used to read the target of the link, failing
1360 * if the file is not a symbolic link. The target of the link need not exist.
1361 * The returned {@code Path} object will be associated with the same file
1362 * system as {@code link}.
1363 *
1364 * @param link
1365 * the path to the symbolic link
1366 *
1367 * @return a {@code Path} object representing the target of the link
1368 *
1369 * @throws UnsupportedOperationException
1370 * if the implementation does not support symbolic links
1371 * @throws NotLinkException
1372 * if the target could otherwise not be read because the file
1373 * is not a symbolic link <i>(optional specific exception)</i>
1374 * @throws IOException
1375 * if an I/O error occurs
1376 * @throws SecurityException
1377 * In the case of the default provider, and a security manager
1378 * is installed, it checks that {@code FilePermission} has been
1379 * granted with the "{@code readlink}" action to read the link.
1380 */
1381 public static Path readSymbolicLink(Path link) throws IOException {
1382 return provider(link).readSymbolicLink(link);
1383 }
1384
1385 /**
1386 * Returns the {@link FileStore} representing the file store where a file
1387 * is located.
1388 *
1389 * <p> Once a reference to the {@code FileStore} is obtained it is
1390 * implementation specific if operations on the returned {@code FileStore},
1391 * or {@link FileStoreAttributeView} objects obtained from it, continue
1392 * to depend on the existence of the file. In particular the behavior is not
1393 * defined for the case that the file is deleted or moved to a different
1394 * file store.
1395 *
1396 * @param path
1397 * the path to the file
1398 *
1399 * @return the file store where the file is stored
1400 *
1401 * @throws IOException
1402 * if an I/O error occurs
1403 * @throws SecurityException
1404 * In the case of the default provider, and a security manager is
1405 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1406 * method is invoked to check read access to the file, and in
1407 * addition it checks {@link RuntimePermission}<tt>
1408 * ("getFileStoreAttributes")</tt>
1409 */
1410 public static FileStore getFileStore(Path path) throws IOException {
1411 return provider(path).getFileStore(path);
1412 }
1413
1414 /**
1415 * Tests if two paths locate the same file.
1416 *
1417 * <p> If both {@code Path} objects are {@link Path#equals(Object) equal}
1418 * then this method returns {@code true} without checking if the file exists.
1419 * If the two {@code Path} objects are associated with different providers
1420 * then this method returns {@code false}. Otherwise, this method checks if
1421 * both {@code Path} objects locate the same file, and depending on the
1422 * implementation, may require to open or access both files.
1423 *
1424 * <p> If the file system and files remain static, then this method implements
1425 * an equivalence relation for non-null {@code Paths}.
1426 * <ul>
1427 * <li>It is <i>reflexive</i>: for {@code Path} {@code f},
1428 * {@code isSameFile(f,f)} should return {@code true}.
1429 * <li>It is <i>symmetric</i>: for two {@code Paths} {@code f} and {@code g},
1430 * {@code isSameFile(f,g)} will equal {@code isSameFile(g,f)}.
1431 * <li>It is <i>transitive</i>: for three {@code Paths}
1432 * {@code f}, {@code g}, and {@code h}, if {@code isSameFile(f,g)} returns
1433 * {@code true} and {@code isSameFile(g,h)} returns {@code true}, then
1434 * {@code isSameFile(f,h)} will return return {@code true}.
1435 * </ul>
1436 *
1437 * @param path
1438 * one path to the file
1439 * @param path2
1440 * the other path
1441 *
1442 * @return {@code true} if, and only if, the two paths locate the same file
1443 *
1444 * @throws IOException
1445 * if an I/O error occurs
1446 * @throws SecurityException
1447 * In the case of the default provider, and a security manager is
1448 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1449 * method is invoked to check read access to both files.
1450 *
1451 * @see java.nio.file.attribute.BasicFileAttributes#fileKey
1452 */
1453 public static boolean isSameFile(Path path, Path path2) throws IOException {
1454 return provider(path).isSameFile(path, path2);
1455 }
1456
1457 /**
1458 * Tells whether or not a file is considered <em>hidden</em>. The exact
1459 * definition of hidden is platform or provider dependent. On UNIX for
1460 * example a file is considered to be hidden if its name begins with a
1461 * period character ('.'). On Windows a file is considered hidden if it
1462 * isn't a directory and the DOS {@link DosFileAttributes#isHidden hidden}
1463 * attribute is set.
1464 *
1465 * <p> Depending on the implementation this method may require to access
1466 * the file system to determine if the file is considered hidden.
1467 *
1468 * @param path
1469 * the path to the file to test
1470 *
1471 * @return {@code true} if the file is considered hidden
1472 *
1473 * @throws IOException
1474 * if an I/O error occurs
1475 * @throws SecurityException
1476 * In the case of the default provider, and a security manager is
1477 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1478 * method is invoked to check read access to the file.
1479 */
1480 public static boolean isHidden(Path path) throws IOException {
1481 return provider(path).isHidden(path);
1482 }
1483
1484 // lazy loading of default and installed file type detectors
1485 private static class FileTypeDetectors{
1486 static final FileTypeDetector defaultFileTypeDetector =
1487 sun.nio.fs.DefaultFileTypeDetector.create();
1488 static final List<FileTypeDetector> installeDetectors =
1489 loadInstalledDetectors();
1490
1491 // loads all installed file type detectors
1492 private static List<FileTypeDetector> loadInstalledDetectors() {
1493 return AccessController
1494 .doPrivileged(new PrivilegedAction<List<FileTypeDetector>>() {
1495 @Override public List<FileTypeDetector> run() {
1496 List<FileTypeDetector> list = new ArrayList<>();
1497 ServiceLoader<FileTypeDetector> loader = ServiceLoader
1498 .load(FileTypeDetector.class, ClassLoader.getSystemClassLoader());
1499 for (FileTypeDetector detector: loader) {
1500 list.add(detector);
1501 }
1502 return list;
1503 }});
1504 }
1505 }
1506
1507 /**
1508 * Probes the content type of a file.
1509 *
1510 * <p> This method uses the installed {@link FileTypeDetector} implementations
1511 * to probe the given file to determine its content type. Each file type
1512 * detector's {@link FileTypeDetector#probeContentType probeContentType} is
1513 * invoked, in turn, to probe the file type. If the file is recognized then
1514 * the content type is returned. If the file is not recognized by any of the
1515 * installed file type detectors then a system-default file type detector is
1516 * invoked to guess the content type.
1517 *
1518 * <p> A given invocation of the Java virtual machine maintains a system-wide
1519 * list of file type detectors. Installed file type detectors are loaded
1520 * using the service-provider loading facility defined by the {@link ServiceLoader}
1521 * class. Installed file type detectors are loaded using the system class
1522 * loader. If the system class loader cannot be found then the extension class
1523 * loader is used; If the extension class loader cannot be found then the
1524 * bootstrap class loader is used. File type detectors are typically installed
1525 * by placing them in a JAR file on the application class path or in the
1526 * extension directory, the JAR file contains a provider-configuration file
1527 * named {@code java.nio.file.spi.FileTypeDetector} in the resource directory
1528 * {@code META-INF/services}, and the file lists one or more fully-qualified
1529 * names of concrete subclass of {@code FileTypeDetector } that have a zero
1530 * argument constructor. If the process of locating or instantiating the
1531 * installed file type detectors fails then an unspecified error is thrown.
1532 * The ordering that installed providers are located is implementation
1533 * specific.
1534 *
1535 * <p> The return value of this method is the string form of the value of a
1536 * Multipurpose Internet Mail Extension (MIME) content type as
1537 * defined by <a href="http://www.ietf.org/rfc/rfc2045.txt"><i>RFC 2045:
1538 * Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet
1539 * Message Bodies</i></a>. The string is guaranteed to be parsable according
1540 * to the grammar in the RFC.
1541 *
1542 * @param path
1543 * the path to the file to probe
1544 *
1545 * @return The content type of the file, or {@code null} if the content
1546 * type cannot be determined
1547 *
1548 * @throws IOException
1549 * if an I/O error occurs
1550 * @throws SecurityException
1551 * If a security manager is installed and it denies an unspecified
1552 * permission required by a file type detector implementation.
1553 */
1554 public static String probeContentType(Path path)
1555 throws IOException
1556 {
1557 // try installed file type detectors
1558 for (FileTypeDetector detector: FileTypeDetectors.installeDetectors) {
1559 String result = detector.probeContentType(path);
1560 if (result != null)
1561 return result;
1562 }
1563
1564 // fallback to default
1565 return FileTypeDetectors.defaultFileTypeDetector.probeContentType(path);
1566 }
1567
1568 // -- File Attributes --
1569
1570 /**
1571 * Returns a file attribute view of a given type.
1572 *
1573 * <p> A file attribute view provides a read-only or updatable view of a
1574 * set of file attributes. This method is intended to be used where the file
1575 * attribute view defines type-safe methods to read or update the file
1576 * attributes. The {@code type} parameter is the type of the attribute view
1577 * required and the method returns an instance of that type if supported.
1578 * The {@link BasicFileAttributeView} type supports access to the basic
1579 * attributes of a file. Invoking this method to select a file attribute
1580 * view of that type will always return an instance of that class.
1581 *
1582 * <p> The {@code options} array may be used to indicate how symbolic links
1583 * are handled by the resulting file attribute view for the case that the
1584 * file is a symbolic link. By default, symbolic links are followed. If the
1585 * option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is present then
1586 * symbolic links are not followed. This option is ignored by implementations
1587 * that do not support symbolic links.
1588 *
1589 * <p> <b>Usage Example:</b>
1590 * Suppose we want read or set a file's ACL, if supported:
1591 * <pre>
1592 * Path path = ...
1593 * AclFileAttributeView view = Files.getFileAttributeView(path, AclFileAttributeView.class);
1594 * if (view != null) {
1595 * List<AclEntry> acl = view.getAcl();
1596 * :
1597 * }
1598 * </pre>
1599 *
1600 *
1601 * @param path
1602 * the path to the file
1603 * @param type
1604 * the {@code Class} object corresponding to the file attribute view
1605 * @param options
1606 * options indicating how symbolic links are handled
1607 *
1608 * @return a file attribute view of the specified type, or {@code null} if
1609 * the attribute view type is not available
1610 */
1611 public static <V extends FileAttributeView> V getFileAttributeView(Path path,
1612 Class<V> type,
1613 LinkOption... options)
1614 {
1615 return provider(path).getFileAttributeView(path, type, options);
1616 }
1617
1618 /**
1619 * Reads a file's attributes as a bulk operation.
1620 *
1621 * <p> The {@code type} parameter is the type of the attributes required
1622 * and this method returns an instance of that type if supported. All
1623 * implementations support a basic set of file attributes and so invoking
1624 * this method with a {@code type} parameter of {@code
1625 * BasicFileAttributes.class} will not throw {@code
1626 * UnsupportedOperationException}.
1627 *
1628 * <p> The {@code options} array may be used to indicate how symbolic links
1629 * are handled for the case that the file is a symbolic link. By default,
1630 * symbolic links are followed and the file attribute of the final target
1631 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1632 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1633 *
1634 * <p> It is implementation specific if all file attributes are read as an
1635 * atomic operation with respect to other file system operations.
1636 *
1637 * <p> <b>Usage Example:</b>
1638 * Suppose we want to read a file's attributes in bulk:
1639 * <pre>
1640 * Path path = ...
1641 * BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class);
1642 * </pre>
1643 * Alternatively, suppose we want to read file's POSIX attributes without
1644 * following symbolic links:
1645 * <pre>
1646 * PosixFileAttributes attrs = Files.readAttributes(path, PosixFileAttributes.class, NOFOLLOW_LINKS);
1647 * </pre>
1648 *
1649 * @param path
1650 * the path to the file
1651 * @param type
1652 * the {@code Class} of the file attributes required
1653 * to read
1654 * @param options
1655 * options indicating how symbolic links are handled
1656 *
1657 * @return the file attributes
1658 *
1659 * @throws UnsupportedOperationException
1660 * if an attributes of the given type are not supported
1661 * @throws IOException
1662 * if an I/O error occurs
1663 * @throws SecurityException
1664 * In the case of the default provider, a security manager is
1665 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1666 * method is invoked to check read access to the file. If this
1667 * method is invoked to read security sensitive attributes then the
1668 * security manager may be invoke to check for additional permissions.
1669 */
1670 public static <A extends BasicFileAttributes> A readAttributes(Path path,
1671 Class<A> type,
1672 LinkOption... options)
1673 throws IOException
1674 {
1675 return provider(path).readAttributes(path, type, options);
1676 }
1677
1678 /**
1679 * Sets the value of a file attribute.
1680 *
1681 * <p> The {@code attribute} parameter identifies the attribute to be set
1682 * and takes the form:
1683 * <blockquote>
1684 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
1685 * </blockquote>
1686 * where square brackets [...] delineate an optional component and the
1687 * character {@code ':'} stands for itself.
1688 *
1689 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1690 * FileAttributeView} that identifies a set of file attributes. If not
1691 * specified then it defaults to {@code "basic"}, the name of the file
1692 * attribute view that identifies the basic set of file attributes common to
1693 * many file systems. <i>attribute-name</i> is the name of the attribute
1694 * within the set.
1695 *
1696 * <p> The {@code options} array may be used to indicate how symbolic links
1697 * are handled for the case that the file is a symbolic link. By default,
1698 * symbolic links are followed and the file attribute of the final target
1699 * of the link is set. If the option {@link LinkOption#NOFOLLOW_LINKS
1700 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1701 *
1702 * <p> <b>Usage Example:</b>
1703 * Suppose we want to set the DOS "hidden" attribute:
1704 * <pre>
1705 * Path path = ...
1706 * Files.setAttribute(path, "dos:hidden", true);
1707 * </pre>
1708 *
1709 * @param path
1710 * the path to the file
1711 * @param attribute
1712 * the attribute to set
1713 * @param value
1714 * the attribute value
1715 * @param options
1716 * options indicating how symbolic links are handled
1717 *
1718 * @return the {@code path} parameter
1719 *
1720 * @throws UnsupportedOperationException
1721 * if the attribute view is not available
1722 * @throws IllegalArgumentException
1723 * if the attribute name is not specified, or is not recognized, or
1724 * the attribute value is of the correct type but has an
1725 * inappropriate value
1726 * @throws ClassCastException
1727 * if the attribute value is not of the expected type or is a
1728 * collection containing elements that are not of the expected
1729 * type
1730 * @throws IOException
1731 * if an I/O error occurs
1732 * @throws SecurityException
1733 * In the case of the default provider, and a security manager is
1734 * installed, its {@link SecurityManager#checkWrite(String) checkWrite}
1735 * method denies write access to the file. If this method is invoked
1736 * to set security sensitive attributes then the security manager
1737 * may be invoked to check for additional permissions.
1738 */
1739 public static Path setAttribute(Path path, String attribute, Object value,
1740 LinkOption... options)
1741 throws IOException
1742 {
1743 provider(path).setAttribute(path, attribute, value, options);
1744 return path;
1745 }
1746
1747 /**
1748 * Reads the value of a file attribute.
1749 *
1750 * <p> The {@code attribute} parameter identifies the attribute to be read
1751 * and takes the form:
1752 * <blockquote>
1753 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
1754 * </blockquote>
1755 * where square brackets [...] delineate an optional component and the
1756 * character {@code ':'} stands for itself.
1757 *
1758 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1759 * FileAttributeView} that identifies a set of file attributes. If not
1760 * specified then it defaults to {@code "basic"}, the name of the file
1761 * attribute view that identifies the basic set of file attributes common to
1762 * many file systems. <i>attribute-name</i> is the name of the attribute.
1763 *
1764 * <p> The {@code options} array may be used to indicate how symbolic links
1765 * are handled for the case that the file is a symbolic link. By default,
1766 * symbolic links are followed and the file attribute of the final target
1767 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1768 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1769 *
1770 * <p> <b>Usage Example:</b>
1771 * Suppose we require the user ID of the file owner on a system that
1772 * supports a "{@code unix}" view:
1773 * <pre>
1774 * Path path = ...
1775 * int uid = (Integer)Files.getAttribute(path, "unix:uid");
1776 * </pre>
1777 *
1778 * @param path
1779 * the path to the file
1780 * @param attribute
1781 * the attribute to read
1782 * @param options
1783 * options indicating how symbolic links are handled
1784 *
1785 * @return the attribute value
1786 *
1787 * @throws UnsupportedOperationException
1788 * if the attribute view is not available
1789 * @throws IllegalArgumentException
1790 * if the attribute name is not specified or is not recognized
1791 * @throws IOException
1792 * if an I/O error occurs
1793 * @throws SecurityException
1794 * In the case of the default provider, and a security manager is
1795 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1796 * method denies read access to the file. If this method is invoked
1797 * to read security sensitive attributes then the security manager
1798 * may be invoked to check for additional permissions.
1799 */
1800 public static Object getAttribute(Path path, String attribute,
1801 LinkOption... options)
1802 throws IOException
1803 {
1804 // only one attribute should be read
1805 if (attribute.indexOf('*') >= 0 || attribute.indexOf(',') >= 0)
1806 throw new IllegalArgumentException(attribute);
1807 Map<String,Object> map = readAttributes(path, attribute, options);
1808 assert map.size() == 1;
1809 String name;
1810 int pos = attribute.indexOf(':');
1811 if (pos == -1) {
1812 name = attribute;
1813 } else {
1814 name = (pos == attribute.length()) ? "" : attribute.substring(pos+1);
1815 }
1816 return map.get(name);
1817 }
1818
1819 /**
1820 * Reads a set of file attributes as a bulk operation.
1821 *
1822 * <p> The {@code attributes} parameter identifies the attributes to be read
1823 * and takes the form:
1824 * <blockquote>
1825 * [<i>view-name</i><b>:</b>]<i>attribute-list</i>
1826 * </blockquote>
1827 * where square brackets [...] delineate an optional component and the
1828 * character {@code ':'} stands for itself.
1829 *
1830 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1831 * FileAttributeView} that identifies a set of file attributes. If not
1832 * specified then it defaults to {@code "basic"}, the name of the file
1833 * attribute view that identifies the basic set of file attributes common to
1834 * many file systems.
1835 *
1836 * <p> The <i>attribute-list</i> component is a comma separated list of
1837 * zero or more names of attributes to read. If the list contains the value
1838 * {@code "*"} then all attributes are read. Attributes that are not supported
1839 * are ignored and will not be present in the returned map. It is
1840 * implementation specific if all attributes are read as an atomic operation
1841 * with respect to other file system operations.
1842 *
1843 * <p> The following examples demonstrate possible values for the {@code
1844 * attributes} parameter:
1845 *
1846 * <blockquote>
1847 * <table border="0">
1848 * <tr>
1849 * <td> {@code "*"} </td>
1850 * <td> Read all {@link BasicFileAttributes basic-file-attributes}. </td>
1851 * </tr>
1852 * <tr>
1853 * <td> {@code "size,lastModifiedTime,lastAccessTime"} </td>
1854 * <td> Reads the file size, last modified time, and last access time
1855 * attributes. </td>
1856 * </tr>
1857 * <tr>
1858 * <td> {@code "posix:*"} </td>
1859 * <td> Read all {@link PosixFileAttributes POSIX-file-attributes}. </td>
1860 * </tr>
1861 * <tr>
1862 * <td> {@code "posix:permissions,owner,size"} </td>
1863 * <td> Reads the POSX file permissions, owner, and file size. </td>
1864 * </tr>
1865 * </table>
1866 * </blockquote>
1867 *
1868 * <p> The {@code options} array may be used to indicate how symbolic links
1869 * are handled for the case that the file is a symbolic link. By default,
1870 * symbolic links are followed and the file attribute of the final target
1871 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1872 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1873 *
1874 * @param path
1875 * the path to the file
1876 * @param attributes
1877 * the attributes to read
1878 * @param options
1879 * options indicating how symbolic links are handled
1880 *
1881 * @return a map of the attributes returned; The map's keys are the
1882 * attribute names, its values are the attribute values
1883 *
1884 * @throws UnsupportedOperationException
1885 * if the attribute view is not available
1886 * @throws IllegalArgumentException
1887 * if no attributes are specified or an unrecognized attributes is
1888 * specified
1889 * @throws IOException
1890 * if an I/O error occurs
1891 * @throws SecurityException
1892 * In the case of the default provider, and a security manager is
1893 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1894 * method denies read access to the file. If this method is invoked
1895 * to read security sensitive attributes then the security manager
1896 * may be invoke to check for additional permissions.
1897 */
1898 public static Map<String,Object> readAttributes(Path path, String attributes,
1899 LinkOption... options)
1900 throws IOException
1901 {
1902 return provider(path).readAttributes(path, attributes, options);
1903 }
1904
1905 /**
1906 * Returns a file's POSIX file permissions.
1907 *
1908 * <p> The {@code path} parameter is associated with a {@code FileSystem}
1909 * that supports the {@link PosixFileAttributeView}. This attribute view
1910 * provides access to file attributes commonly associated with files on file
1911 * systems used by operating systems that implement the Portable Operating
1912 * System Interface (POSIX) family of standards.
1913 *
1914 * <p> The {@code options} array may be used to indicate how symbolic links
1915 * are handled for the case that the file is a symbolic link. By default,
1916 * symbolic links are followed and the file attribute of the final target
1917 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1918 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1919 *
1920 * @param path
1921 * the path to the file
1922 * @param options
1923 * options indicating how symbolic links are handled
1924 *
1925 * @return the file permissions
1926 *
1927 * @throws UnsupportedOperationException
1928 * if the associated file system does not support the {@code
1929 * PosixFileAttributeView}
1930 * @throws IOException
1931 * if an I/O error occurs
1932 * @throws SecurityException
1933 * In the case of the default provider, a security manager is
1934 * installed, and it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
1935 * or its {@link SecurityManager#checkRead(String) checkRead} method
1936 * denies read access to the file.
1937 */
1938 public static Set<PosixFilePermission> getPosixFilePermissions(Path path,
1939 LinkOption... options)
1940 throws IOException
1941 {
1942 return readAttributes(path, PosixFileAttributes.class, options).permissions();
1943 }
1944
1945 /**
1946 * Sets a file's POSIX permissions.
1947 *
1948 * <p> The {@code path} parameter is associated with a {@code FileSystem}
1949 * that supports the {@link PosixFileAttributeView}. This attribute view
1950 * provides access to file attributes commonly associated with files on file
1951 * systems used by operating systems that implement the Portable Operating
1952 * System Interface (POSIX) family of standards.
1953 *
1954 * @param path
1955 * A file reference that locates the file
1956 * @param perms
1957 * The new set of permissions
1958 *
1959 * @throws UnsupportedOperationException
1960 * if the associated file system does not support the {@code
1961 * PosixFileAttributeView}
1962 * @throws ClassCastException
1963 * if the sets contains elements that are not of type {@code
1964 * PosixFilePermission}
1965 * @throws IOException
1966 * if an I/O error occurs
1967 * @throws SecurityException
1968 * In the case of the default provider, and a security manager is
1969 * installed, it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
1970 * or its {@link SecurityManager#checkWrite(String) checkWrite}
1971 * method denies write access to the file.
1972 */
1973 public static Path setPosixFilePermissions(Path path,
1974 Set<PosixFilePermission> perms)
1975 throws IOException
1976 {
1977 PosixFileAttributeView view =
1978 getFileAttributeView(path, PosixFileAttributeView.class);
1979 if (view == null)
1980 throw new UnsupportedOperationException();
1981 view.setPermissions(perms);
1982 return path;
1983 }
1984
1985 /**
1986 * Returns the owner of a file.
1987 *
1988 * <p> The {@code path} parameter is associated with a file system that
1989 * supports {@link FileOwnerAttributeView}. This file attribute view provides
1990 * access to a file attribute that is the owner of the file.
1991 *
1992 * @param path
1993 * A file reference that locates the file
1994 * @param options
1995 * options indicating how symbolic links are handled
1996 *
1997 * @return A user principal representing the owner of the file
1998 *
1999 * @throws UnsupportedOperationException
2000 * if the associated file system does not support the {@code
2001 * FileOwnerAttributeView}
2002 * @throws IOException
2003 * if an I/O error occurs
2004 * @throws SecurityException
2005 * In the case of the default provider, and a security manager is
2006 * installed, it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
2007 * or its {@link SecurityManager#checkRead(String) checkRead} method
2008 * denies read access to the file.
2009 */
2010 public static UserPrincipal getOwner(Path path, LinkOption... options) throws IOException {
2011 FileOwnerAttributeView view =
2012 getFileAttributeView(path, FileOwnerAttributeView.class, options);
2013 if (view == null)
2014 throw new UnsupportedOperationException();
2015 return view.getOwner();
2016 }
2017
2018 /**
2019 * Updates the file owner.
2020 *
2021 * <p> The {@code path} parameter is associated with a file system that
2022 * supports {@link FileOwnerAttributeView}. This file attribute view provides
2023 * access to a file attribute that is the owner of the file.
2024 *
2025 * <p> <b>Usage Example:</b>
2026 * Suppose we want to make "joe" the owner of a file:
2027 * <pre>
2028 * Path path = ...
2029 * UserPrincipalLookupService lookupService =
2030 * provider(path).getUserPrincipalLookupService();
2031 * UserPrincipal joe = lookupService.lookupPrincipalByName("joe");
2032 * Files.setOwner(path, joe);
2033 * </pre>
2034 *
2035 * @param path
2036 * A file reference that locates the file
2037 * @param owner
2038 * The new file owner
2039 *
2040 * @throws UnsupportedOperationException
2041 * if the associated file system does not support the {@code
2042 * FileOwnerAttributeView}
2043 * @throws IOException
2044 * if an I/O error occurs
2045 * @throws SecurityException
2046 * In the case of the default provider, and a security manager is
2047 * installed, it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
2048 * or its {@link SecurityManager#checkWrite(String) checkWrite}
2049 * method denies write access to the file.
2050 *
2051 * @see FileSystem#getUserPrincipalLookupService
2052 * @see java.nio.file.attribute.UserPrincipalLookupService
2053 */
2054 public static Path setOwner(Path path, UserPrincipal owner)
2055 throws IOException
2056 {
2057 FileOwnerAttributeView view =
2058 getFileAttributeView(path, FileOwnerAttributeView.class);
2059 if (view == null)
2060 throw new UnsupportedOperationException();
2061 view.setOwner(owner);
2062 return path;
2063 }
2064
2065 /**
2066 * Tests whether a file is a symbolic link.
2067 *
2068 * <p> Where is it required to distinguish an I/O exception from the case
2069 * that the file is not a symbolic link then the file attributes can be
2070 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2071 * readAttributes} method and the file type tested with the {@link
2072 * BasicFileAttributes#isSymbolicLink} method.
2073 *
2074 * @return {@code true} if the file is a symbolic link; {@code false} if
2075 * the file does not exist, is not a symbolic link, or it cannot
2076 * be determined if the file is a symbolic link or not.
2077 *
2078 * @throws SecurityException
2079 * In the case of the default provider, and a security manager is
2080 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2081 * method denies read access to the file.
2082 */
2083 public static boolean isSymbolicLink(Path path) {
2084 try {
2085 return readAttributes(path,
2086 BasicFileAttributes.class,
2087 LinkOption.NOFOLLOW_LINKS).isSymbolicLink();
2088 } catch (IOException ioe) {
2089 return false;
2090 }
2091 }
2092
2093 /**
2094 * Tests whether a file is a directory.
2095 *
2096 * <p> The {@code options} array may be used to indicate how symbolic links
2097 * are handled for the case that the file is a symbolic link. By default,
2098 * symbolic links are followed and the file attribute of the final target
2099 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2100 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2101 *
2102 * <p> Where is it required to distinguish an I/O exception from the case
2103 * that the file is not a directory then the file attributes can be
2104 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2105 * readAttributes} method and the file type tested with the {@link
2106 * BasicFileAttributes#isDirectory} method.
2107 *
2108 * @param path
2109 * the path to the file to test
2110 * @param options
2111 * options indicating how symbolic links are handled
2112 *
2113 * @return {@code true} if the file is a directory; {@code false} if
2114 * the file does not exist, is not a directory, or it cannot
2115 * be determined if the file is a directory or not.
2116 *
2117 * @throws SecurityException
2118 * In the case of the default provider, and a security manager is
2119 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2120 * method denies read access to the file.
2121 */
2122 public static boolean isDirectory(Path path, LinkOption... options) {
2123 try {
2124 return readAttributes(path, BasicFileAttributes.class, options).isDirectory();
2125 } catch (IOException ioe) {
2126 return false;
2127 }
2128 }
2129
2130 /**
2131 * Tests whether a file is a regular file with opaque content.
2132 *
2133 * <p> The {@code options} array may be used to indicate how symbolic links
2134 * are handled for the case that the file is a symbolic link. By default,
2135 * symbolic links are followed and the file attribute of the final target
2136 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2137 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2138 *
2139 * <p> Where is it required to distinguish an I/O exception from the case
2140 * that the file is not a regular file then the file attributes can be
2141 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2142 * readAttributes} method and the file type tested with the {@link
2143 * BasicFileAttributes#isRegularFile} method.
2144 *
2145 * @param path
2146 * the path to the file
2147 * @param options
2148 * options indicating how symbolic links are handled
2149 *
2150 * @return {@code true} if the file is a regular file; {@code false} if
2151 * the file does not exist, is not a regular file, or it
2152 * cannot be determined if the file is a regular file or not.
2153 *
2154 * @throws SecurityException
2155 * In the case of the default provider, and a security manager is
2156 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2157 * method denies read access to the file.
2158 */
2159 public static boolean isRegularFile(Path path, LinkOption... options) {
2160 try {
2161 return readAttributes(path, BasicFileAttributes.class, options).isRegularFile();
2162 } catch (IOException ioe) {
2163 return false;
2164 }
2165 }
2166
2167 /**
2168 * Returns a file's last modified time.
2169 *
2170 * <p> The {@code options} array may be used to indicate how symbolic links
2171 * are handled for the case that the file is a symbolic link. By default,
2172 * symbolic links are followed and the file attribute of the final target
2173 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2174 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2175 *
2176 * @param path
2177 * the path to the file
2178 * @param options
2179 * options indicating how symbolic links are handled
2180 *
2181 * @return a {@code FileTime} representing the time the file was last
2182 * modified, or an implementation specific default when a time
2183 * stamp to indicate the time of last modification is not supported
2184 * by the file system
2185 *
2186 * @throws IOException
2187 * if an I/O error occurs
2188 * @throws SecurityException
2189 * In the case of the default provider, and a security manager is
2190 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2191 * method denies read access to the file.
2192 *
2193 * @see BasicFileAttributes#lastModifiedTime
2194 */
2195 public static FileTime getLastModifiedTime(Path path, LinkOption... options)
2196 throws IOException
2197 {
2198 return readAttributes(path, BasicFileAttributes.class, options).lastModifiedTime();
2199 }
2200
2201 /**
2202 * Updates a file's last modified time attribute. The file time is converted
2203 * to the epoch and precision supported by the file system. Converting from
2204 * finer to coarser granularities result in precision loss. The behavior of
2205 * this method when attempting to set the last modified time when it is not
2206 * supported by the file system or is outside the range supported by the
2207 * underlying file store is not defined. It may or not fail by throwing an
2208 * {@code IOException}.
2209 *
2210 * <p> <b>Usage Example:</b>
2211 * Suppose we want to set the last modified time to the current time:
2212 * <pre>
2213 * Path path = ...
2214 * FileTime now = FileTime.fromMillis(System.currentTimeMillis());
2215 * Files.setLastModifiedTime(path, now);
2216 * </pre>
2217 *
2218 * @param path
2219 * the path to the file
2220 * @param time
2221 * the new last modified time
2222 *
2223 * @return the file
2224 *
2225 * @throws IOException
2226 * if an I/O error occurs
2227 * @throws SecurityException
2228 * In the case of the default provider, the security manager's {@link
2229 * SecurityManager#checkWrite(String) checkWrite} method is invoked
2230 * to check write access to file
2231 *
2232 * @see BasicFileAttributeView#setTimes
2233 */
2234 public static Path setLastModifiedTime(Path path, FileTime time)
2235 throws IOException
2236 {
2237 getFileAttributeView(path, BasicFileAttributeView.class)
2238 .setTimes(time, null, null);
2239 return path;
2240 }
2241
2242 /**
2243 * Returns the size of a file (in bytes). The size may differ from the
2244 * actual size on the file system due to compression, support for sparse
2245 * files, or other reasons. The size of files that are not {@link
2246 * #isRegularFile regular} files is implementation specific and
2247 * therefore unspecified.
2248 *
2249 * @param path
2250 * the path to the file
2251 *
2252 * @return the file size, in bytes
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#size
2262 */
2263 public static long size(Path path) throws IOException {
2264 return readAttributes(path, BasicFileAttributes.class).size();
2265 }
2266
2267 // -- Accessibility --
2268
2269 /**
2270 * Returns {@code false} if NOFOLLOW_LINKS is present.
2271 */
2272 private static boolean followLinks(LinkOption... options) {
2273 boolean followLinks = true;
2274 for (LinkOption opt: options) {
2275 if (opt == LinkOption.NOFOLLOW_LINKS) {
2276 followLinks = false;
2277 continue;
2278 }
2279 if (opt == null)
2280 throw new NullPointerException();
2281 throw new AssertionError("Should not get here");
2282 }
2283 return followLinks;
2284 }
2285
2286 /**
2287 * Tests whether a file exists.
2288 *
2289 * <p> The {@code options} parameter may be used to indicate how symbolic links
2290 * are handled for the case that the file is a symbolic link. By default,
2291 * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
2292 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2293 *
2294 * <p> Note that the result of this method is immediately outdated. If this
2295 * method indicates the file exists then there is no guarantee that a
2296 * subsequence access will succeed. Care should be taken when using this
2297 * method in security sensitive applications.
2298 *
2299 * @param path
2300 * the path to the file to test
2301 * @param options
2302 * options indicating how symbolic links are handled
2303 * .
2304 * @return {@code true} if the file exists; {@code false} if the file does
2305 * not exist or its existence cannot be determined.
2306 *
2307 * @throws SecurityException
2308 * In the case of the default provider, the {@link
2309 * SecurityManager#checkRead(String)} is invoked to check
2310 * read access to the file.
2311 *
2312 * @see #notExists
2313 */
2314 public static boolean exists(Path path, LinkOption... options) {
2315 try {
2316 if (followLinks(options)) {
2317 provider(path).checkAccess(path);
2318 } else {
2319 // attempt to read attributes without following links
2320 readAttributes(path, BasicFileAttributes.class,
2321 LinkOption.NOFOLLOW_LINKS);
2322 }
2323 // file exists
2324 return true;
2325 } catch (IOException x) {
2326 // does not exist or unable to determine if file exists
2327 return false;
2328 }
2329
2330 }
2331
2332 /**
2333 * Tests whether the file located by this path does not exist. This method
2334 * is intended for cases where it is required to take action when it can be
2335 * confirmed that a file does not exist.
2336 *
2337 * <p> The {@code options} parameter may be used to indicate how symbolic links
2338 * are handled for the case that the file is a symbolic link. By default,
2339 * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
2340 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2341 *
2342 * <p> Note that this method is not the complement of the {@link #exists
2343 * exists} method. Where it is not possible to determine if a file exists
2344 * or not then both methods return {@code false}. As with the {@code exists}
2345 * method, the result of this method is immediately outdated. If this
2346 * method indicates the file does exist then there is no guarantee that a
2347 * subsequence attempt to create the file will succeed. Care should be taken
2348 * when using this method in security sensitive applications.
2349 *
2350 * @param path
2351 * the path to the file to test
2352 * @param options
2353 * options indicating how symbolic links are handled
2354 *
2355 * @return {@code true} if the file does not exist; {@code false} if the
2356 * file exists or its existence cannot be determined
2357 *
2358 * @throws SecurityException
2359 * In the case of the default provider, the {@link
2360 * SecurityManager#checkRead(String)} is invoked to check
2361 * read access to the file.
2362 */
2363 public static boolean notExists(Path path, LinkOption... options) {
2364 try {
2365 if (followLinks(options)) {
2366 provider(path).checkAccess(path);
2367 } else {
2368 // attempt to read attributes without following links
2369 readAttributes(path, BasicFileAttributes.class,
2370 LinkOption.NOFOLLOW_LINKS);
2371 }
2372 // file exists
2373 return false;
2374 } catch (NoSuchFileException x) {
2375 // file confirmed not to exist
2376 return true;
2377 } catch (IOException x) {
2378 return false;
2379 }
2380 }
2381
2382 /**
2383 * Used by isReadbale, isWritable, isExecutable to test access to a file.
2384 */
2385 private static boolean isAccessible(Path path, AccessMode... modes) {
2386 try {
2387 provider(path).checkAccess(path, modes);
2388 return true;
2389 } catch (IOException x) {
2390 return false;
2391 }
2392 }
2393
2394 /**
2395 * Tests whether a file is readable. This method checks that a file exists
2396 * and that this Java virtual machine has appropriate privileges that would
2397 * allow it open the file for reading. Depending on the implementation, this
2398 * method may require to read file permissions, access control lists, or
2399 * other file attributes in order to check the effective access to the file.
2400 * Consequently, this method may not be atomic with respect to other file
2401 * system operations.
2402 *
2403 * <p> Note that the result of this method is immediately outdated, there is
2404 * no guarantee that a subsequent attempt to open the file for reading will
2405 * succeed (or even that it will access the same file). Care should be taken
2406 * when using this method in security sensitive applications.
2407 *
2408 * @param path
2409 * the path to the file to check
2410 *
2411 * @return {@code true} if the file exists and is readable; {@code false}
2412 * if the file does not exist, read access would be denied because
2413 * the Java virtual machine has insufficient privileges, or access
2414 * cannot be determined
2415 *
2416 * @throws SecurityException
2417 * In the case of the default provider, and a security manager is
2418 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2419 * is invoked to check read access to the file.
2420 */
2421 public static boolean isReadable(Path path) {
2422 return isAccessible(path, AccessMode.READ);
2423 }
2424
2425 /**
2426 * Tests whether a file is writable. This method checks that a file exists
2427 * and that this Java virtual machine has appropriate privileges that would
2428 * allow it open the file for writing. Depending on the implementation, this
2429 * method may require to read file permissions, access control lists, or
2430 * other file attributes in order to check the effective access to the file.
2431 * Consequently, this method may not be atomic with respect to other file
2432 * system operations.
2433 *
2434 * <p> Note that result of this method is immediately outdated, there is no
2435 * guarantee that a subsequent attempt to open the file for writing will
2436 * succeed (or even that it will access the same file). Care should be taken
2437 * when using this method in security sensitive applications.
2438 *
2439 * @param path
2440 * the path to the file to check
2441 *
2442 * @return {@code true} if the file exists and is writable; {@code false}
2443 * if the file does not exist, write access would be denied because
2444 * the Java virtual machine has insufficient privileges, or access
2445 * cannot be determined
2446 *
2447 * @throws SecurityException
2448 * In the case of the default provider, and a security manager is
2449 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2450 * is invoked to check write access to the file.
2451 */
2452 public static boolean isWritable(Path path) {
2453 return isAccessible(path, AccessMode.WRITE);
2454 }
2455
2456 /**
2457 * Tests whether a file is executable. This method checks that a file exists
2458 * and that this Java virtual machine has appropriate privileges to {@link
2459 * Runtime#exec execute} the file. The semantics may differ when checking
2460 * access to a directory. For example, on UNIX systems, checking for
2461 * execute access checks that the Java virtual machine has permission to
2462 * search the directory in order to access file or subdirectories.
2463 *
2464 * <p> Depending on the implementation, this method may require to read file
2465 * permissions, access control lists, or other file attributes in order to
2466 * check the effective access to the file. Consequently, this method may not
2467 * be atomic with respect to other file system operations.
2468 *
2469 * <p> Note that the result of this method is immediately outdated, there is
2470 * no guarantee that a subsequent attempt to execute the file will succeed
2471 * (or even that it will access the same file). Care should be taken when
2472 * using this method in security sensitive applications.
2473 *
2474 * @param path
2475 * the path to the file to check
2476 *
2477 * @return {@code true} if the file exists and is executable; {@code false}
2478 * if the file does not exist, execute access would be denied because
2479 * the Java virtual machine has insufficient privileges, or access
2480 * cannot be determined
2481 *
2482 * @throws SecurityException
2483 * In the case of the default provider, and a security manager is
2484 * installed, the {@link SecurityManager#checkExec(String)
2485 * checkExec} is invoked to check execute access to the file.
2486 */
2487 public static boolean isExecutable(Path path) {
2488 return isAccessible(path, AccessMode.EXECUTE);
2489 }
2490
2491 // -- Recursive operations --
2492
2493 /**
2494 * Walks a file tree.
2495 *
2496 * <p> This method walks a file tree rooted at a given starting file. The
2497 * file tree traversal is <em>depth-first</em> with the given {@link
2498 * FileVisitor} invoked for each file encountered. File tree traversal
2499 * completes when all accessible files in the tree have been visited, or a
2500 * visit method returns a result of {@link FileVisitResult#TERMINATE
2501 * TERMINATE}. Where a visit method terminates due an {@code IOException},
2502 * an uncaught error, or runtime exception, then the traversal is terminated
2503 * and the error or exception is propagated to the caller of this method.
2504 *
2505 * <p> For each file encountered this method attempts to read its {@link
2506 * java.nio.file.attribute.BasicFileAttributes}. If the file is not a
2507 * directory then the {@link FileVisitor#visitFile visitFile} method is
2508 * invoked with the file attributes. If the file attributes cannot be read,
2509 * due to an I/O exception, then the {@link FileVisitor#visitFileFailed
2510 * visitFileFailed} method is invoked with the I/O exception.
2511 *
2512 * <p> Where the file is a directory, and the directory could not be opened,
2513 * then the {@code visitFileFailed} method is invoked with the I/O exception,
2514 * after which, the file tree walk continues, by default, at the next
2515 * <em>sibling</em> of the directory.
2516 *
2517 * <p> Where the directory is opened successfully, then the entries in the
2518 * directory, and their <em>descendants</em> are visited. When all entries
2519 * have been visited, or an I/O error occurs during iteration of the
2520 * directory, then the directory is closed and the visitor's {@link
2521 * FileVisitor#postVisitDirectory postVisitDirectory} method is invoked.
2522 * The file tree walk then continues, by default, at the next <em>sibling</em>
2523 * of the directory.
2524 *
2525 * <p> By default, symbolic links are not automatically followed by this
2526 * method. If the {@code options} parameter contains the {@link
2527 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then symbolic links are
2528 * followed. When following links, and the attributes of the target cannot
2529 * be read, then this method attempts to get the {@code BasicFileAttributes}
2530 * of the link. If they can be read then the {@code visitFile} method is
2531 * invoked with the attributes of the link (otherwise the {@code visitFileFailed}
2532 * method is invoked as specified above).
2533 *
2534 * <p> If the {@code options} parameter contains the {@link
2535 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then this method keeps
2536 * track of directories visited so that cycles can be detected. A cycle
2537 * arises when there is an entry in a directory that is an ancestor of the
2538 * directory. Cycle detection is done by recording the {@link
2539 * java.nio.file.attribute.BasicFileAttributes#fileKey file-key} of directories,
2540 * or if file keys are not available, by invoking the {@link #isSameFile
2541 * isSameFile} method to test if a directory is the same file as an
2542 * ancestor. When a cycle is detected it is treated as an I/O error, and the
2543 * {@link FileVisitor#visitFileFailed visitFileFailed} method is invoked with
2544 * an instance of {@link FileSystemLoopException}.
2545 *
2546 * <p> The {@code maxDepth} parameter is the maximum number of levels of
2547 * directories to visit. A value of {@code 0} means that only the starting
2548 * file is visited, unless denied by the security manager. A value of
2549 * {@link Integer#MAX_VALUE MAX_VALUE} may be used to indicate that all
2550 * levels should be visited. The {@code visitFile} method is invoked for all
2551 * files, including directories, encountered at {@code maxDepth}, unless the
2552 * basic file attributes cannot be read, in which case the {@code
2553 * visitFileFailed} method is invoked.
2554 *
2555 * <p> If a visitor returns a result of {@code null} then {@code
2556 * NullPointerException} is thrown.
2557 *
2558 * <p> When a security manager is installed and it denies access to a file
2559 * (or directory), then it is ignored and the visitor is not invoked for
2560 * that file (or directory).
2561 *
2562 * @param start
2563 * the starting file
2564 * @param options
2565 * options to configure the traversal
2566 * @param maxDepth
2567 * the maximum number of directory levels to visit
2568 * @param visitor
2569 * the file visitor to invoke for each file
2570 *
2571 * @return the starting file
2572 *
2573 * @throws IllegalArgumentException
2574 * if the {@code maxDepth} parameter is negative
2575 * @throws SecurityException
2576 * If the security manager denies access to the starting file.
2577 * In the case of the default provider, the {@link
2578 * SecurityManager#checkRead(String) checkRead} method is invoked
2579 * to check read access to the directory.
2580 * @throws IOException
2581 * if an I/O error is thrown by a visitor method
2582 */
2583 public static Path walkFileTree(Path start,
2584 Set<FileVisitOption> options,
2585 int maxDepth,
2586 FileVisitor<? super Path> visitor)
2587 throws IOException
2588 {
2589 if (maxDepth < 0)
2590 throw new IllegalArgumentException("'maxDepth' is negative");
2591 new FileTreeWalker(options, visitor, maxDepth).walk(start);
2592 return start;
2593 }
2594
2595 /**
2596 * Walks a file tree.
2597 *
2598 * <p> This method works as if invoking it were equivalent to evaluating the
2599 * expression:
2600 * <blockquote><pre>
2601 * walkFileTree(start, EnumSet.noneOf(FileVisitOption.class), Integer.MAX_VALUE, visitor)
2602 * </pre></blockquote>
2603 * In other words, it does not follow symbolic links, and visits all levels
2604 * of the file tree.
2605 *
2606 * @param start
2607 * the starting file
2608 * @param visitor
2609 * the file visitor to invoke for each file
2610 *
2611 * @return the starting file
2612 *
2613 * @throws SecurityException
2614 * If the security manager denies access to the starting file.
2615 * In the case of the default provider, the {@link
2616 * SecurityManager#checkRead(String) checkRead} method is invoked
2617 * to check read access to the directory.
2618 * @throws IOException
2619 * if an I/O error is thrown by a visitor method
2620 */
2621 public static Path walkFileTree(Path start, FileVisitor<? super Path> visitor)
2622 throws IOException
2623 {
2624 return walkFileTree(start,
2625 EnumSet.noneOf(FileVisitOption.class),
2626 Integer.MAX_VALUE,
2627 visitor);
2628 }
2629
2630
2631 // -- Utility methods for simple usages --
2632
2633 // buffer size used for reading and writing
2634 private static final int BUFFER_SIZE = 8192;
2635
2636 /**
2637 * Opens a file for reading, returning a {@code BufferedReader} that may be
2638 * used to read text from the file in an efficient manner. Bytes from the
2639 * file are decoded into characters using the specified charset. Reading
2640 * commences at the beginning of the file.
2641 *
2642 * <p> The {@code Reader} methods that read from the file throw {@code
2643 * IOException} if a malformed or unmappable byte sequence is read.
2644 *
2645 * @param path
2646 * the path to the file
2647 * @param cs
2648 * the charset to use for decoding
2649 *
2650 * @return a new buffered reader, with default buffer size, to read text
2651 * from the file
2652 *
2653 * @throws IOException
2654 * if an I/O error occurs opening the file
2655 * @throws SecurityException
2656 * In the case of the default provider, and a security manager is
2657 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2658 * method is invoked to check read access to the file.
2659 *
2660 * @see #readAllLines
2661 */
2662 public static BufferedReader newBufferedReader(Path path, Charset cs)
2663 throws IOException
2664 {
2665 CharsetDecoder decoder = cs.newDecoder();
2666 Reader reader = new InputStreamReader(newInputStream(path), decoder);
2667 return new BufferedReader(reader);
2668 }
2669
2670 /**
2671 * Opens or creates a file for writing, returning a {@code BufferedWriter}
2672 * that may be used to write text to the file in an efficient manner.
2673 * The {@code options} parameter specifies how the the file is created or
2674 * opened. If no options are present then this method works as if the {@link
2675 * StandardOpenOption#CREATE CREATE}, {@link
2676 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
2677 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
2678 * opens the file for writing, creating the file if it doesn't exist, or
2679 * initially truncating an existing {@link #isRegularFile regular-file} to
2680 * a size of {@code 0} if it exists.
2681 *
2682 * <p> The {@code Writer} methods to write text throw {@code IOException}
2683 * if the text cannot be encoded using the specified charset.
2684 *
2685 * @param path
2686 * the path to the file
2687 * @param cs
2688 * the charset to use for encoding
2689 * @param options
2690 * options specifying how the file is opened
2691 *
2692 * @return a new buffered writer, with default buffer size, to write text
2693 * to the file
2694 *
2695 * @throws IOException
2696 * if an I/O error occurs opening or creating the file
2697 * @throws UnsupportedOperationException
2698 * if an unsupported option is specified
2699 * @throws SecurityException
2700 * In the case of the default provider, and a security manager is
2701 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2702 * method is invoked to check write access to the file.
2703 *
2704 * @see #write(Path,Iterable,Charset,OpenOption[])
2705 */
2706 public static BufferedWriter newBufferedWriter(Path path, Charset cs,
2707 OpenOption... options)
2708 throws IOException
2709 {
2710 CharsetEncoder encoder = cs.newEncoder();
2711 Writer writer = new OutputStreamWriter(newOutputStream(path, options), encoder);
2712 return new BufferedWriter(writer);
2713 }
2714
2715 /**
2716 * Reads all bytes from an input stream and writes them to an output stream.
2717 */
2718 private static long copy(InputStream source, OutputStream sink)
2719 throws IOException
2720 {
2721 long nread = 0L;
2722 byte[] buf = new byte[BUFFER_SIZE];
2723 int n;
2724 while ((n = source.read(buf)) > 0) {
2725 sink.write(buf, 0, n);
2726 nread += n;
2727 }
2728 return nread;
2729 }
2730
2731 /**
2732 * Copies all bytes from an input stream to a file. On return, the input
2733 * stream will be at end of stream.
2734 *
2735 * <p> By default, the copy fails if the target file already exists or is a
2736 * symbolic link. If the {@link StandardCopyOption#REPLACE_EXISTING
2737 * REPLACE_EXISTING} option is specified, and the target file already exists,
2738 * then it is replaced if it is not a non-empty directory. If the target
2739 * file exists and is a symbolic link, then the symbolic link is replaced.
2740 * In this release, the {@code REPLACE_EXISTING} option is the only option
2741 * required to be supported by this method. Additional options may be
2742 * supported in future releases.
2743 *
2744 * <p> If an I/O error occurs reading from the input stream or writing to
2745 * the file, then it may do so after the target file has been created and
2746 * after some bytes have been read or written. Consequently the input
2747 * stream may not be at end of stream and may be in an inconsistent state.
2748 * It is strongly recommended that the input stream be promptly closed if an
2749 * I/O error occurs.
2750 *
2751 * <p> This method may block indefinitely reading from the input stream (or
2752 * writing to the file). The behavior for the case that the input stream is
2753 * <i>asynchronously closed</i> or the thread interrupted during the copy is
2754 * highly input stream and file system provider specific and therefore not
2755 * specified.
2756 *
2757 * <p> <b>Usage example</b>: Suppose we want to capture a web page and save
2758 * it to a file:
2759 * <pre>
2760 * Path path = ...
2761 * URI u = URI.create("http://java.sun.com/");
2762 * try (InputStream in = u.toURL().openStream()) {
2763 * Files.copy(in, path);
2764 * }
2765 * </pre>
2766 *
2767 * @param in
2768 * the input stream to read from
2769 * @param target
2770 * the path to the file
2771 * @param options
2772 * options specifying how the copy should be done
2773 *
2774 * @return the number of bytes read or written
2775 *
2776 * @throws IOException
2777 * if an I/O error occurs when reading or writing
2778 * @throws FileAlreadyExistsException
2779 * if the target file exists but cannot be replaced because the
2780 * {@code REPLACE_EXISTING} option is not specified <i>(optional
2781 * specific exception)</i>
2782 * @throws DirectoryNotEmptyException
2783 * the {@code REPLACE_EXISTING} option is specified but the file
2784 * cannot be replaced because it is a non-empty directory
2785 * <i>(optional specific exception)</i> *
2786 * @throws UnsupportedOperationException
2787 * if {@code options} contains a copy option that is not supported
2788 * @throws SecurityException
2789 * In the case of the default provider, and a security manager is
2790 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2791 * method is invoked to check write access to the file. Where the
2792 * {@code REPLACE_EXISTING} option is specified, the security
2793 * manager's {@link SecurityManager#checkDelete(String) checkDelete}
2794 * method is invoked to check that an existing file can be deleted.
2795 */
2796 public static long copy(InputStream in, Path target, CopyOption... options)
2797 throws IOException
2798 {
2799 // ensure not null before opening file
2800 Objects.requireNonNull(in);
2801
2802 // check for REPLACE_EXISTING
2803 boolean replaceExisting = false;
2804 for (CopyOption opt: options) {
2805 if (opt == StandardCopyOption.REPLACE_EXISTING) {
2806 replaceExisting = true;
2807 } else {
2808 if (opt == null) {
2809 throw new NullPointerException("options contains 'null'");
2810 } else {
2811 throw new UnsupportedOperationException(opt + " not supported");
2812 }
2813 }
2814 }
2815
2816 // attempt to delete an existing file
2817 SecurityException se = null;
2818 if (replaceExisting) {
2819 try {
2820 deleteIfExists(target);
2821 } catch (SecurityException x) {
2822 se = x;
2823 }
2824 }
2825
2826 // attempt to create target file. If it fails with
2827 // FileAlreadyExistsException then it may be because the security
2828 // manager prevented us from deleting the file, in which case we just
2829 // throw the SecurityException.
2830 OutputStream ostream;
2831 try {
2832 ostream = newOutputStream(target, StandardOpenOption.CREATE_NEW,
2833 StandardOpenOption.WRITE);
2834 } catch (FileAlreadyExistsException x) {
2835 if (se != null)
2836 throw se;
2837 // someone else won the race and created the file
2838 throw x;
2839 }
2840
2841 // do the copy
2842 try (OutputStream out = ostream) {
2843 return copy(in, out);
2844 }
2845 }
2846
2847 /**
2848 * Copies all bytes from a file to an output stream.
2849 *
2850 * <p> If an I/O error occurs reading from the file or writing to the output
2851 * stream, then it may do so after some bytes have been read or written.
2852 * Consequently the output stream may be in an inconsistent state. It is
2853 * strongly recommended that the output stream be promptly closed if an I/O
2854 * error occurs.
2855 *
2856 * <p> This method may block indefinitely writing to the output stream (or
2857 * reading from the file). The behavior for the case that the output stream
2858 * is <i>asynchronously closed</i> or the thread interrupted during the copy
2859 * is highly output stream and file system provider specific and therefore
2860 * not specified.
2861 *
2862 * <p> Note that if the given output stream is {@link java.io.Flushable}
2863 * then its {@link java.io.Flushable#flush flush} method may need to invoked
2864 * after this method completes so as to flush any buffered output.
2865 *
2866 * @param source
2867 * the path to the file
2868 * @param out
2869 * the output stream to write to
2870 *
2871 * @return the number of bytes read or written
2872 *
2873 * @throws IOException
2874 * if an I/O error occurs when reading or writing
2875 * @throws SecurityException
2876 * In the case of the default provider, and a security manager is
2877 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2878 * method is invoked to check read access to the file.
2879 */
2880 public static long copy(Path source, OutputStream out) throws IOException {
2881 // ensure not null before opening file
2882 Objects.requireNonNull(out);
2883
2884 try (InputStream in = newInputStream(source)) {
2885 return copy(in, out);
2886 }
2887 }
2888
2889 /**
2890 * Read all the bytes from an input stream. The {@code initialSize}
2891 * parameter indicates the initial size of the byte[] to allocate.
2892 */
2893 private static byte[] read(InputStream source, int initialSize)
2894 throws IOException
2895 {
2896 int capacity = initialSize;
2897 byte[] buf = new byte[capacity];
2898 int nread = 0;
2899 int rem = buf.length;
2900 int n;
2901 // read to EOF which may read more or less than initialSize (eg: file
2902 // is truncated while we are reading)
2903 while ((n = source.read(buf, nread, rem)) > 0) {
2904 nread += n;
2905 rem -= n;
2906 assert rem >= 0;
2907 if (rem == 0) {
2908 // need larger buffer
2909 int newCapacity = capacity << 1;
2910 if (newCapacity < 0) {
2911 if (capacity == Integer.MAX_VALUE)
2912 throw new OutOfMemoryError("Required array size too large");
2913 newCapacity = Integer.MAX_VALUE;
2914 }
2915 rem = newCapacity - capacity;
2916 buf = Arrays.copyOf(buf, newCapacity);
2917 capacity = newCapacity;
2918 }
2919 }
2920 return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
2921 }
2922
2923 /**
2924 * Read all the bytes from a file. The method ensures that the file is
2925 * closed when all bytes have been read or an I/O error, or other runtime
2926 * exception, is thrown.
2927 *
2928 * <p> Note that this method is intended for simple cases where it is
2929 * convenient to read all bytes into a byte array. It is not intended for
2930 * reading in large files.
2931 *
2932 * @param path
2933 * the path to the file
2934 *
2935 * @return a byte array containing the bytes read from the file
2936 *
2937 * @throws IOException
2938 * if an I/O error occurs reading from the stream
2939 * @throws OutOfMemoryError
2940 * if an array of the required size cannot be allocated, for
2941 * example the file is larger that {@code 2GB}
2942 * @throws SecurityException
2943 * In the case of the default provider, and a security manager is
2944 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2945 * method is invoked to check read access to the file.
2946 */
2947 public static byte[] readAllBytes(Path path) throws IOException {
2948 long size = size(path);
2949 if (size > (long)Integer.MAX_VALUE)
2950 throw new OutOfMemoryError("Required array size too large");
2951
2952 try (InputStream in = newInputStream(path)) {
2953 return read(in, (int)size);
2954 }
2955 }
2956
2957 /**
2958 * Read all lines from a file. This method ensures that the file is
2959 * closed when all bytes have been read or an I/O error, or other runtime
2960 * exception, is thrown. Bytes from the file are decoded into characters
2961 * using the specified charset.
2962 *
2963 * <p> This method recognizes the following as line terminators:
2964 * <ul>
2965 * <li> <code>\u000D</code> followed by <code>\u000A</code>,
2966 * CARRIAGE RETURN followed by LINE FEED </li>
2967 * <li> <code>\u000A</code>, LINE FEED </li>
2968 * <li> <code>\u000D</code>, CARRIAGE RETURN </li>
2969 * </ul>
2970 * <p> Additional Unicode line terminators may be recognized in future
2971 * releases.
2972 *
2973 * <p> Note that this method is intended for simple cases where it is
2974 * convenient to read all lines in a single operation. It is not intended
2975 * for reading in large files.
2976 *
2977 * @param path
2978 * the path to the file
2979 * @param cs
2980 * the charset to use for decoding
2981 *
2982 * @return the lines from the file as a {@code List}; whether the {@code
2983 * List} is modifiable or not is implementation dependent and
2984 * therefore not specified
2985 *
2986 * @throws IOException
2987 * if an I/O error occurs reading from the file or a malformed or
2988 * unmappable byte sequence is read
2989 * @throws SecurityException
2990 * In the case of the default provider, and a security manager is
2991 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2992 * method is invoked to check read access to the file.
2993 *
2994 * @see #newBufferedReader
2995 */
2996 public static List<String> readAllLines(Path path, Charset cs)
2997 throws IOException
2998 {
2999 try (BufferedReader reader = newBufferedReader(path, cs)) {
3000 List<String> result = new ArrayList<>();
3001 for (;;) {
3002 String line = reader.readLine();
3003 if (line == null)
3004 break;
3005 result.add(line);
3006 }
3007 return result;
3008 }
3009 }
3010
3011 /**
3012 * Writes bytes to a file. The {@code options} parameter specifies how the
3013 * the file is created or opened. If no options are present then this method
3014 * works as if the {@link StandardOpenOption#CREATE CREATE}, {@link
3015 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3016 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3017 * opens the file for writing, creating the file if it doesn't exist, or
3018 * initially truncating an existing {@link #isRegularFile regular-file} to
3019 * a size of {@code 0}. All bytes in the byte array are written to the file.
3020 * The method ensures that the file is closed when all bytes have been
3021 * written (or an I/O error or other runtime exception is thrown). If an I/O
3022 * error occurs then it may do so after the file has created or truncated,
3023 * or after some bytes have been written to the file.
3024 *
3025 * <p> <b>Usage example</b>: By default the method creates a new file or
3026 * overwrites an existing file. Suppose you instead want to append bytes
3027 * to an existing file:
3028 * <pre>
3029 * Path path = ...
3030 * byte[] bytes = ...
3031 * Files.write(path, bytes, StandardOpenOption.APPEND);
3032 * </pre>
3033 *
3034 * @param path
3035 * the path to the file
3036 * @param bytes
3037 * the byte array with the bytes to write
3038 * @param options
3039 * options specifying how the file is opened
3040 *
3041 * @return the path
3042 *
3043 * @throws IOException
3044 * if an I/O error occurs writing to or creating the file
3045 * @throws UnsupportedOperationException
3046 * if an unsupported option is specified
3047 * @throws SecurityException
3048 * In the case of the default provider, and a security manager is
3049 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3050 * method is invoked to check write access to the file.
3051 */
3052 public static Path write(Path path, byte[] bytes, OpenOption... options)
3053 throws IOException
3054 {
3055 // ensure bytes is not null before opening file
3056 Objects.requireNonNull(bytes);
3057
3058 try (OutputStream out = Files.newOutputStream(path, options)) {
3059 int len = bytes.length;
3060 int rem = len;
3061 while (rem > 0) {
3062 int n = Math.min(rem, BUFFER_SIZE);
3063 out.write(bytes, (len-rem), n);
3064 rem -= n;
3065 }
3066 }
3067 return path;
3068 }
3069
3070 /**
3071 * Write lines of text to a file. Each line is a char sequence and is
3072 * written to the file in sequence with each line terminated by the
3073 * platform's line separator, as defined by the system property {@code
3074 * line.separator}. Characters are encoded into bytes using the specified
3075 * charset.
3076 *
3077 * <p> The {@code options} parameter specifies how the the file is created
3078 * or opened. If no options are present then this method works as if the
3079 * {@link StandardOpenOption#CREATE CREATE}, {@link
3080 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3081 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3082 * opens the file for writing, creating the file if it doesn't exist, or
3083 * initially truncating an existing {@link #isRegularFile regular-file} to
3084 * a size of {@code 0}. The method ensures that the file is closed when all
3085 * lines have been written (or an I/O error or other runtime exception is
3086 * thrown). If an I/O error occurs then it may do so after the file has
3087 * created or truncated, or after some bytes have been written to the file.
3088 *
3089 * @param path
3090 * the path to the file
3091 * @param lines
3092 * an object to iterate over the char sequences
3093 * @param cs
3094 * the charset to use for encoding
3095 * @param options
3096 * options specifying how the file is opened
3097 *
3098 * @return the path
3099 *
3100 * @throws IOException
3101 * if an I/O error occurs writing to or creating the file, or the
3102 * text cannot be encoded using the specified charset
3103 * @throws UnsupportedOperationException
3104 * if an unsupported option is specified
3105 * @throws SecurityException
3106 * In the case of the default provider, and a security manager is
3107 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3108 * method is invoked to check write access to the file.
3109 */
3110 public static Path write(Path path, Iterable<? extends CharSequence> lines,
3111 Charset cs, OpenOption... options)
3112 throws IOException
3113 {
3114 // ensure lines is not null before opening file
3115 Objects.requireNonNull(lines);
3116 CharsetEncoder encoder = cs.newEncoder();
3117 OutputStream out = newOutputStream(path, options);
3118 try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, encoder))) {
3119 for (CharSequence line: lines) {
3120 writer.append(line);
3121 writer.newLine();
3122 }
3123 }
3124 return path;
3125 }
3126 }