1 /*
2 * Copyright (c) 2007, 2010, 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<<SetPosixFilePermission>> 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 /**
367 * Opens a directory, returning a {@link DirectoryStream} to iterate over
368 * all entries in the directory. The elements returned by the directory
369 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
370 * Path}, each one representing an entry in the directory. The {@code Path}
371 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
372 * name of the directory entry against {@code dir}.
373 *
374 * <p> When not using the try-with-resources construct, then directory
375 * stream's {@code close} method should be invoked after iteration is
376 * completed so as to free any resources held for the open directory.
377 *
378 * <p> When an implementation supports operations on entries in the
379 * directory that execute in a race-free manner then the returned directory
380 * stream is a {@link SecureDirectoryStream}.
381 *
382 * @param dir
383 * the path to the directory
384 *
385 * @return a new and open {@code DirectoryStream} object
386 *
387 * @throws NotDirectoryException
388 * if the file could not otherwise be opened because it is not
389 * a directory <i>(optional specific exception)</i>
390 * @throws IOException
391 * if an I/O error occurs
392 * @throws SecurityException
393 * In the case of the default provider, and a security manager is
394 * installed, the {@link SecurityManager#checkRead(String) checkRead}
395 * method is invoked to check read access to the directory.
396 */
397 public static DirectoryStream<Path> newDirectoryStream(Path dir)
398 throws IOException
399 {
400 return provider(dir).newDirectoryStream(dir, new DirectoryStream.Filter<Path>() {
401 @Override
402 public boolean accept(Path entry) {
403 return true;
404 }
405 });
406 }
407
408 /**
409 * Opens a directory, returning a {@link DirectoryStream} to iterate over
410 * the entries in the directory. The elements returned by the directory
411 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
412 * Path}, each one representing an entry in the directory. The {@code Path}
413 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
414 * name of the directory entry against {@code dir}. The entries returned by
415 * the iterator are filtered by matching the {@code String} representation
416 * of their file names against the given <em>globbing</em> pattern.
417 *
418 * <p> For example, suppose we want to iterate over the files ending with
419 * ".java" in a directory:
420 * <pre>
421 * Path dir = ...
422 * try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, "*.java")) {
423 * :
424 * }
425 * </pre>
426 *
427 * <p> The globbing pattern is specified by the {@link
428 * FileSystem#getPathMatcher getPathMatcher} method.
429 *
430 * <p> When not using the try-with-resources construct, then directory
431 * stream's {@code close} method should be invoked after iteration is
432 * completed so as to free any resources held for the open directory.
433 *
434 * <p> When an implementation supports operations on entries in the
435 * directory that execute in a race-free manner then the returned directory
436 * stream is a {@link SecureDirectoryStream}.
437 *
438 * @param dir
439 * the path to the directory
440 * @param glob
441 * the glob pattern
442 *
443 * @return a new and open {@code DirectoryStream} object
444 *
445 * @throws java.util.regex.PatternSyntaxException
446 * if the pattern is invalid
447 * @throws NotDirectoryException
448 * if the file could not otherwise be opened because it is not
449 * a directory <i>(optional specific exception)</i>
450 * @throws IOException
451 * if an I/O error occurs
452 * @throws SecurityException
453 * In the case of the default provider, and a security manager is
454 * installed, the {@link SecurityManager#checkRead(String) checkRead}
455 * method is invoked to check read access to the directory.
456 */
457 public static DirectoryStream<Path> newDirectoryStream(Path dir, String glob)
458 throws IOException
459 {
460 // avoid creating a matcher if all entries are required.
461 if (glob.equals("*"))
462 return newDirectoryStream(dir);
463
464 // create a matcher and return a filter that uses it.
465 FileSystem fs = dir.getFileSystem();
466 final PathMatcher matcher = fs.getPathMatcher("glob:" + glob);
467 DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
468 @Override
469 public boolean accept(Path entry) {
470 return matcher.matches(entry.getFileName());
471 }
472 };
473 return fs.provider().newDirectoryStream(dir, filter);
474 }
475
476 /**
477 * Opens a directory, returning a {@link DirectoryStream} to iterate over
478 * the entries in the directory. The elements returned by the directory
479 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
480 * Path}, each one representing an entry in the directory. The {@code Path}
481 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
482 * name of the directory entry against {@code dir}. The entries returned by
483 * the iterator are filtered by the given {@link DirectoryStream.Filter
484 * filter}.
485 *
486 * <p> When not using the try-with-resources construct, then directory
487 * stream's {@code close} method should be invoked after iteration is
488 * completed so as to free any resources held for the open directory.
489 *
490 * <p> Where the filter terminates due to an uncaught error or runtime
491 * exception then it is propagated to the {@link Iterator#hasNext()
492 * hasNext} or {@link Iterator#next() next} method. Where an {@code
493 * IOException} is thrown, it results in the {@code hasNext} or {@code
494 * next} method throwing a {@link DirectoryIteratorException} with the
495 * {@code IOException} as the cause.
496 *
497 * <p> When an implementation supports operations on entries in the
498 * directory that execute in a race-free manner then the returned directory
499 * stream is a {@link SecureDirectoryStream}.
500 *
501 * <p> <b>Usage Example:</b>
502 * Suppose we want to iterate over the files in a directory that are
503 * larger than 8K.
504 * <pre>
505 * DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
506 * public boolean accept(Path file) throws IOException {
507 * return (Files.size(file) > 8192L);
508 * }
509 * };
510 * Path dir = ...
511 * try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, filter)) {
512 * :
513 * }
514 * </pre>
515 *
516 * @param dir
517 * the path to the directory
518 * @param filter
519 * the directory stream filter
520 *
521 * @return a new and open {@code DirectoryStream} object
522 *
523 * @throws NotDirectoryException
524 * if the file could not otherwise be opened because it is not
525 * a directory <i>(optional specific exception)</i>
526 * @throws IOException
527 * if an I/O error occurs
528 * @throws SecurityException
529 * In the case of the default provider, and a security manager is
530 * installed, the {@link SecurityManager#checkRead(String) checkRead}
531 * method is invoked to check read access to the directory.
532 */
533 public static DirectoryStream<Path> newDirectoryStream(Path dir,
534 DirectoryStream.Filter<? super Path> filter)
535 throws IOException
536 {
537 return provider(dir).newDirectoryStream(dir, filter);
538 }
539
540 // -- Creation and deletion --
541
542 /**
543 * Creates a new and empty file, failing if the file already exists. The
544 * check for the existence of the file and the creation of the new file if
545 * it does not exist are a single operation that is atomic with respect to
546 * all other filesystem activities that might affect the directory.
547 *
548 * <p> The {@code attrs} parameter is optional {@link FileAttribute
549 * file-attributes} to set atomically when creating the file. Each attribute
550 * is identified by its {@link FileAttribute#name name}. If more than one
551 * attribute of the same name is included in the array then all but the last
552 * occurrence is ignored.
553 *
554 * @param path
555 * the path to the file to create
556 * @param attrs
557 * an optional list of file attributes to set atomically when
558 * creating the file
559 *
560 * @return the file
561 *
562 * @throws UnsupportedOperationException
563 * if the array contains an attribute that cannot be set atomically
564 * when creating the file
565 * @throws FileAlreadyExistsException
566 * if a file of that name already exists
567 * <i>(optional specific exception)</i>
568 * @throws IOException
569 * if an I/O error occurs or the parent directory does not exist
570 * @throws SecurityException
571 * In the case of the default provider, and a security manager is
572 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
573 * method is invoked to check write access to the new file.
574 */
575 public static Path createFile(Path path, FileAttribute<?>... attrs)
576 throws IOException
577 {
578 EnumSet<StandardOpenOption> options =
579 EnumSet.<StandardOpenOption>of(StandardOpenOption.CREATE_NEW, StandardOpenOption.WRITE);
580 newByteChannel(path, options, attrs).close();
581 return path;
582 }
583
584 /**
585 * Creates a new directory. The check for the existence of the file and the
586 * creation of the directory if it does not exist are a single operation
587 * that is atomic with respect to all other filesystem activities that might
588 * affect the directory. The {@link #createDirectories createDirectories}
589 * method should be used where it is required to create all nonexistent
590 * parent directories first.
591 *
592 * <p> The {@code attrs} parameter is optional {@link FileAttribute
593 * file-attributes} to set atomically when creating the directory. Each
594 * attribute is identified by its {@link FileAttribute#name name}. If more
595 * than one attribute of the same name is included in the array then all but
596 * the last occurrence is ignored.
597 *
598 * @param dir
599 * the directory to create
600 * @param attrs
601 * an optional list of file attributes to set atomically when
602 * creating the directory
603 *
604 * @return the directory
605 *
606 * @throws UnsupportedOperationException
607 * if the array contains an attribute that cannot be set atomically
608 * when creating the directory
609 * @throws FileAlreadyExistsException
610 * if a directory could not otherwise be created because a file of
611 * that name already exists <i>(optional specific exception)</i>
612 * @throws IOException
613 * if an I/O error occurs or the parent directory does not exist
614 * @throws SecurityException
615 * In the case of the default provider, and a security manager is
616 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
617 * method is invoked to check write access to the new directory.
618 */
619 public static Path createDirectory(Path dir, FileAttribute<?>... attrs)
620 throws IOException
621 {
622 provider(dir).createDirectory(dir, attrs);
623 return dir;
624 }
625
626 /**
627 * Creates a directory by creating all nonexistent parent directories first.
628 * Unlike the {@link #createDirectory createDirectory} method, an exception
629 * is not thrown if the directory could not be created because it already
630 * exists.
631 *
632 * <p> The {@code attrs} parameter is optional {@link FileAttribute
633 * file-attributes} to set atomically when creating the nonexistent
634 * directories. Each file attribute is identified by its {@link
635 * FileAttribute#name name}. If more than one attribute of the same name is
636 * included in the array then all but the last occurrence is ignored.
637 *
638 * <p> If this method fails, then it may do so after creating some, but not
639 * all, of the parent directories.
640 *
641 * @param dir
642 * the directory to create
643 *
644 * @param attrs
645 * an optional list of file attributes to set atomically when
646 * creating the directory
647 *
648 * @return the directory
649 *
650 * @throws UnsupportedOperationException
651 * if the array contains an attribute that cannot be set atomically
652 * when creating the directory
653 * @throws FileAlreadyExistsException
654 * if {@code dir} exists but is not a directory <i>(optional specific
655 * exception)</i>
656 * @throws IOException
657 * if an I/O error occurs
658 * @throws SecurityException
659 * in the case of the default provider, and a security manager is
660 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
661 * method is invoked prior to attempting to create a directory and
662 * its {@link SecurityManager#checkRead(String) checkRead} is
663 * invoked for each parent directory that is checked. If {@code
664 * dir} is not an absolute path then its {@link Path#toAbsolutePath
665 * toAbsolutePath} may need to be invoked to get its absolute path.
666 * This may invoke the security manager's {@link
667 * SecurityManager#checkPropertyAccess(String) checkPropertyAccess}
668 * method to check access to the system property {@code user.dir}
669 */
670 public static Path createDirectories(Path dir, FileAttribute<?>... attrs)
671 throws IOException
672 {
673 // attempt to create the directory
674 try {
675 createAndCheckIsDirectory(dir, attrs);
676 return dir;
677 } catch (FileAlreadyExistsException x) {
678 // file exists and is not a directory
679 throw x;
680 } catch (IOException x) {
681 // parent may not exist or other reason
682 }
683 SecurityException se = null;
684 try {
685 dir = dir.toAbsolutePath();
686 } catch (SecurityException x) {
687 // don't have permission to get absolute path
688 se = x;
689 }
690 // find a decendent that exists
691 Path parent = dir.getParent();
692 while (parent != null) {
693 try {
694 provider(parent).checkAccess(parent);
695 break;
696 } catch (NoSuchFileException x) {
697 // does not exist
698 }
699 parent = parent.getParent();
700 }
701 if (parent == null) {
702 // unable to find existing parent
703 if (se != null)
704 throw se;
705 throw new IOException("Root directory does not exist");
706 }
707
708 // create directories
709 Path child = parent;
710 for (Path name: parent.relativize(dir)) {
711 child = child.resolve(name);
712 createAndCheckIsDirectory(child, attrs);
713 }
714 return dir;
715 }
716
717 /**
718 * Used by createDirectories to attempt to create a directory. A no-op
719 * if the directory already exists.
720 */
721 private static void createAndCheckIsDirectory(Path dir,
722 FileAttribute<?>... attrs)
723 throws IOException
724 {
725 try {
726 createDirectory(dir, attrs);
727 } catch (FileAlreadyExistsException x) {
728 if (!isDirectory(dir, LinkOption.NOFOLLOW_LINKS))
729 throw x;
730 }
731 }
732
733 /**
734 * Creates a new empty file in the specified directory, using the given
735 * prefix and suffix strings to generate its name. The resulting
736 * {@code Path} is associated with the same {@code FileSystem} as the given
737 * directory.
738 *
739 * <p> The details as to how the name of the file is constructed is
740 * implementation dependent and therefore not specified. Where possible
741 * the {@code prefix} and {@code suffix} are used to construct candidate
742 * names in the same manner as the {@link
743 * java.io.File#createTempFile(String,String,File)} method.
744 *
745 * <p> As with the {@code File.createTempFile} methods, this method is only
746 * part of a temporary-file facility. Where used as a <em>work files</em>,
747 * the resulting file may be opened using the {@link
748 * StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE} option so that the
749 * file is deleted when the appropriate {@code close} method is invoked.
750 * Alternatively, a {@link Runtime#addShutdownHook shutdown-hook}, or the
751 * {@link java.io.File#deleteOnExit} mechanism may be used to delete the
752 * file automatically.
753 *
754 * <p> The {@code attrs} parameter is optional {@link FileAttribute
755 * file-attributes} to set atomically when creating the file. Each attribute
756 * is identified by its {@link FileAttribute#name name}. If more than one
757 * attribute of the same name is included in the array then all but the last
758 * occurrence is ignored. When no file attributes are specified, then the
759 * resulting file may have more restrictive access permissions to files
760 * created by the {@link java.io.File#createTempFile(String,String,File)}
761 * method.
762 *
763 * @param dir
764 * the path to directory in which to create the file
765 * @param prefix
766 * the prefix string to be used in generating the file's name;
767 * may be {@code null}
768 * @param suffix
769 * the suffix string to be used in generating the file's name;
770 * may be {@code null}, in which case "{@code .tmp}" is used
771 * @param attrs
772 * an optional list of file attributes to set atomically when
773 * creating the file
774 *
775 * @return the path to the newly created file that did not exist before
776 * this method was invoked
777 *
778 * @throws IllegalArgumentException
779 * if the prefix or suffix parameters cannot be used to generate
780 * a candidate file name
781 * @throws UnsupportedOperationException
782 * if the array contains an attribute that cannot be set atomically
783 * when creating the directory
784 * @throws IOException
785 * if an I/O error occurs or {@code dir} does not exist
786 * @throws SecurityException
787 * In the case of the default provider, and a security manager is
788 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
789 * method is invoked to check write access to the file.
790 */
791 public static Path createTempFile(Path dir,
792 String prefix,
793 String suffix,
794 FileAttribute<?>... attrs)
795 throws IOException
796 {
797 return TempFileHelper.createTempFile(Objects.requireNonNull(dir),
798 prefix, suffix, attrs);
799 }
800
801 /**
802 * Creates an empty file in the default temporary-file directory, using
803 * the given prefix and suffix to generate its name. The resulting {@code
804 * Path} is associated with the default {@code FileSystem}.
805 *
806 * <p> This method works in exactly the manner specified by the
807 * {@link #createTempFile(Path,String,String,FileAttribute[])} method for
808 * the case that the {@code dir} parameter is the temporary-file directory.
809 *
810 * @param prefix
811 * the prefix string to be used in generating the file's name;
812 * may be {@code null}
813 * @param suffix
814 * the suffix string to be used in generating the file's name;
815 * may be {@code null}, in which case "{@code .tmp}" is used
816 * @param attrs
817 * an optional list of file attributes to set atomically when
818 * creating the file
819 *
820 * @return the path to the newly created file that did not exist before
821 * this method was invoked
822 *
823 * @throws IllegalArgumentException
824 * if the prefix or suffix parameters cannot be used to generate
825 * a candidate file name
826 * @throws UnsupportedOperationException
827 * if the array contains an attribute that cannot be set atomically
828 * when creating the directory
829 * @throws IOException
830 * if an I/O error occurs or the temporary-file directory does not
831 * exist
832 * @throws SecurityException
833 * In the case of the default provider, and a security manager is
834 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
835 * method is invoked to check write access to the file.
836 */
837 public static Path createTempFile(String prefix,
838 String suffix,
839 FileAttribute<?>... attrs)
840 throws IOException
841 {
842 return TempFileHelper.createTempFile(null, prefix, suffix, attrs);
843 }
844
845 /**
846 * Creates a new directory in the specified directory, using the given
847 * prefix to generate its name. The resulting {@code Path} is associated
848 * with the same {@code FileSystem} as the given directory.
849 *
850 * <p> The details as to how the name of the directory is constructed is
851 * implementation dependent and therefore not specified. Where possible
852 * the {@code prefix} is used to construct candidate names.
853 *
854 * <p> As with the {@code createTempFile} methods, this method is only
855 * part of a temporary-file facility. A {@link Runtime#addShutdownHook
856 * shutdown-hook}, or the {@link java.io.File#deleteOnExit} mechanism may be
857 * used to delete the directory automatically.
858 *
859 * <p> The {@code attrs} parameter is optional {@link FileAttribute
860 * file-attributes} to set atomically when creating the directory. Each
861 * attribute is identified by its {@link FileAttribute#name name}. If more
862 * than one attribute of the same name is included in the array then all but
863 * the last occurrence is ignored.
864 *
865 * @param dir
866 * the path to directory in which to create the directory
867 * @param prefix
868 * the prefix string to be used in generating the directory's name;
869 * may be {@code null}
870 * @param attrs
871 * an optional list of file attributes to set atomically when
872 * creating the directory
873 *
874 * @return the path to the newly created directory that did not exist before
875 * this method was invoked
876 *
877 * @throws IllegalArgumentException
878 * if the prefix cannot be used to generate a candidate directory name
879 * @throws UnsupportedOperationException
880 * if the array contains an attribute that cannot be set atomically
881 * when creating the directory
882 * @throws IOException
883 * if an I/O error occurs or {@code dir} does not exist
884 * @throws SecurityException
885 * In the case of the default provider, and a security manager is
886 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
887 * method is invoked to check write access when creating the
888 * directory.
889 */
890 public static Path createTempDirectory(Path dir,
891 String prefix,
892 FileAttribute<?>... attrs)
893 throws IOException
894 {
895 return TempFileHelper.createTempDirectory(Objects.requireNonNull(dir),
896 prefix, attrs);
897 }
898
899 /**
900 * Creates a new directory in the default temporary-file directory, using
901 * the given prefix to generate its name. The resulting {@code Path} is
902 * associated with the default {@code FileSystem}.
903 *
904 * <p> This method works in exactly the manner specified by {@link
905 * #createTempDirectory(Path,String,FileAttribute[])} method for the case
906 * that the {@code dir} parameter is the temporary-file directory.
907 *
908 * @param prefix
909 * the prefix string to be used in generating the directory's name;
910 * may be {@code null}
911 * @param attrs
912 * an optional list of file attributes to set atomically when
913 * creating the directory
914 *
915 * @return the path to the newly created directory that did not exist before
916 * this method was invoked
917 *
918 * @throws IllegalArgumentException
919 * if the prefix cannot be used to generate a candidate directory name
920 * @throws UnsupportedOperationException
921 * if the array contains an attribute that cannot be set atomically
922 * when creating the directory
923 * @throws IOException
924 * if an I/O error occurs or the temporary-file directory does not
925 * exist
926 * @throws SecurityException
927 * In the case of the default provider, and a security manager is
928 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
929 * method is invoked to check write access when creating the
930 * directory.
931 */
932 public static Path createTempDirectory(String prefix,
933 FileAttribute<?>... attrs)
934 throws IOException
935 {
936 return TempFileHelper.createTempDirectory(null, prefix, attrs);
937 }
938
939 /**
940 * Creates a symbolic link to a target <i>(optional operation)</i>.
941 *
942 * <p> The {@code target} parameter is the target of the link. It may be an
943 * {@link Path#isAbsolute absolute} or relative path and may not exist. When
944 * the target is a relative path then file system operations on the resulting
945 * link are relative to the path of the link.
946 *
947 * <p> The {@code attrs} parameter is optional {@link FileAttribute
948 * attributes} to set atomically when creating the link. Each attribute is
949 * identified by its {@link FileAttribute#name name}. If more than one attribute
950 * of the same name is included in the array then all but the last occurrence
951 * is ignored.
952 *
953 * <p> Where symbolic links are supported, but the underlying {@link FileStore}
954 * does not support symbolic links, then this may fail with an {@link
955 * IOException}. Additionally, some operating systems may require that the
956 * Java virtual machine be started with implementation specific privileges to
957 * create symbolic links, in which case this method may throw {@code IOException}.
958 *
959 * @param link
960 * the path of the symbolic link to create
961 * @param target
962 * the target of the symbolic link
963 * @param attrs
964 * the array of attributes to set atomically when creating the
965 * symbolic link
966 *
967 * @return the path to the symbolic link
968 *
969 * @throws UnsupportedOperationException
970 * if the implementation does not support symbolic links or the
971 * array contains an attribute that cannot be set atomically when
972 * creating the symbolic link
973 * @throws FileAlreadyExistsException
974 * if a file with the name already exists <i>(optional specific
975 * exception)</i>
976 * @throws IOException
977 * if an I/O error occurs
978 * @throws SecurityException
979 * In the case of the default provider, and a security manager
980 * is installed, it denies {@link LinkPermission}<tt>("symbolic")</tt>
981 * or its {@link SecurityManager#checkWrite(String) checkWrite}
982 * method denies write access to the path of the symbolic link.
983 */
984 public static Path createSymbolicLink(Path link, Path target,
985 FileAttribute<?>... attrs)
986 throws IOException
987 {
988 provider(link).createSymbolicLink(link, target, attrs);
989 return link;
990 }
991
992 /**
993 * Creates a new link (directory entry) for an existing file <i>(optional
994 * operation)</i>.
995 *
996 * <p> The {@code link} parameter locates the directory entry to create.
997 * The {@code existing} parameter is the path to an existing file. This
998 * method creates a new directory entry for the file so that it can be
999 * accessed using {@code link} as the path. On some file systems this is
1000 * known as creating a "hard link". Whether the file attributes are
1001 * maintained for the file or for each directory entry is file system
1002 * specific and therefore not specified. Typically, a file system requires
1003 * that all links (directory entries) for a file be on the same file system.
1004 * Furthermore, on some platforms, the Java virtual machine may require to
1005 * be started with implementation specific privileges to create hard links
1006 * or to create links to directories.
1007 *
1008 * @param link
1009 * the link (directory entry) to create
1010 * @param existing
1011 * a path to an existing file
1012 *
1013 * @return the path to the link (directory entry)
1014 *
1015 * @throws UnsupportedOperationException
1016 * if the implementation does not support adding an existing file
1017 * to a directory
1018 * @throws FileAlreadyExistsException
1019 * if the entry could not otherwise be created because a file of
1020 * that name already exists <i>(optional specific exception)</i>
1021 * @throws IOException
1022 * if an I/O error occurs
1023 * @throws SecurityException
1024 * In the case of the default provider, and a security manager
1025 * is installed, it denies {@link LinkPermission}<tt>("hard")</tt>
1026 * or its {@link SecurityManager#checkWrite(String) checkWrite}
1027 * method denies write access to either the link or the
1028 * existing file.
1029 */
1030 public static Path createLink(Path link, Path existing) throws IOException {
1031 provider(link).createLink(link, existing);
1032 return link;
1033 }
1034
1035 /**
1036 * Deletes a file.
1037 *
1038 * <p> An implementation may require to examine the file to determine if the
1039 * file is a directory. Consequently this method may not be atomic with respect
1040 * to other file system operations. If the file is a symbolic link then the
1041 * symbolic link itself, not the final target of the link, is deleted.
1042 *
1043 * <p> If the file is a directory then the directory must be empty. In some
1044 * implementations a directory has entries for special files or links that
1045 * are created when the directory is created. In such implementations a
1046 * directory is considered empty when only the special entries exist.
1047 * This method can be used with the {@link #walkFileTree walkFileTree}
1048 * method to delete a directory and all entries in the directory, or an
1049 * entire <i>file-tree</i> where required.
1050 *
1051 * <p> On some operating systems it may not be possible to remove a file when
1052 * it is open and in use by this Java virtual machine or other programs.
1053 *
1054 * @param path
1055 * the path to the file to delete
1056 *
1057 * @throws NoSuchFileException
1058 * if the file does not exist <i>(optional specific exception)</i>
1059 * @throws DirectoryNotEmptyException
1060 * if the file is a directory and could not otherwise be deleted
1061 * because the directory is not empty <i>(optional specific
1062 * exception)</i>
1063 * @throws IOException
1064 * if an I/O error occurs
1065 * @throws SecurityException
1066 * In the case of the default provider, and a security manager is
1067 * installed, the {@link SecurityManager#checkDelete(String)} method
1068 * is invoked to check delete access to the file
1069 */
1070 public static void delete(Path path) throws IOException {
1071 provider(path).delete(path);
1072 }
1073
1074 /**
1075 * Deletes a file if it exists.
1076 *
1077 * <p> As with the {@link #delete(Path) delete(Path)} method, an
1078 * implementation may need to examine the file to determine if the file is a
1079 * directory. Consequently this method may not be atomic with respect to
1080 * other file system operations. If the file is a symbolic link, then the
1081 * symbolic link itself, not the final target of the link, is deleted.
1082 *
1083 * <p> If the file is a directory then the directory must be empty. In some
1084 * implementations a directory has entries for special files or links that
1085 * are created when the directory is created. In such implementations a
1086 * directory is considered empty when only the special entries exist.
1087 *
1088 * <p> On some operating systems it may not be possible to remove a file when
1089 * it is open and in use by this Java virtual machine or other programs.
1090 *
1091 * @param path
1092 * the path to the file to delete
1093 *
1094 * @return {@code true} if the file was deleted by this method; {@code
1095 * false} if the file could not be deleted because it did not
1096 * exist
1097 *
1098 * @throws DirectoryNotEmptyException
1099 * if the file is a directory and could not otherwise be deleted
1100 * because the directory is not empty <i>(optional specific
1101 * exception)</i>
1102 * @throws IOException
1103 * if an I/O error occurs
1104 * @throws SecurityException
1105 * In the case of the default provider, and a security manager is
1106 * installed, the {@link SecurityManager#checkDelete(String)} method
1107 * is invoked to check delete access to the file.
1108 */
1109 public static boolean deleteIfExists(Path path) throws IOException {
1110 return provider(path).deleteIfExists(path);
1111 }
1112
1113 // -- Copying and moving files --
1114
1115 /**
1116 * Copy a file to a target file.
1117 *
1118 * <p> This method copies a file to the target file with the {@code
1119 * options} parameter specifying how the copy is performed. By default, the
1120 * copy fails if the target file already exists or is a symbolic link,
1121 * except if the source and target are the {@link #isSameFile same} file, in
1122 * which case the method completes without copying the file. File attributes
1123 * are not required to be copied to the target file. If symbolic links are
1124 * supported, and the file is a symbolic link, then the final target of the
1125 * link is copied. If the file is a directory then it creates an empty
1126 * directory in the target location (entries in the directory are not
1127 * copied). This method can be used with the {@link #walkFileTree
1128 * walkFileTree} method to copy a directory and all entries in the directory,
1129 * or an entire <i>file-tree</i> where required.
1130 *
1131 * <p> The {@code options} parameter may include any of the following:
1132 *
1133 * <table border=1 cellpadding=5 summary="">
1134 * <tr> <th>Option</th> <th>Description</th> </tr>
1135 * <tr>
1136 * <td> {@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING} </td>
1137 * <td> If the target file exists, then the target file is replaced if it
1138 * is not a non-empty directory. If the target file exists and is a
1139 * symbolic link, then the symbolic link itself, not the target of
1140 * the link, is replaced. </td>
1141 * </tr>
1142 * <tr>
1143 * <td> {@link StandardCopyOption#COPY_ATTRIBUTES COPY_ATTRIBUTES} </td>
1144 * <td> Attempts to copy the file attributes associated with this file to
1145 * the target file. The exact file attributes that are copied is platform
1146 * and file system dependent and therefore unspecified. Minimally, the
1147 * {@link BasicFileAttributes#lastModifiedTime last-modified-time} is
1148 * copied to the target file if supported by both the source and target
1149 * file store. Copying of file timestamps may result in precision
1150 * loss. </td>
1151 * </tr>
1152 * <tr>
1153 * <td> {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} </td>
1154 * <td> Symbolic links are not followed. If the file is a symbolic link,
1155 * then the symbolic link itself, not the target of the link, is copied.
1156 * It is implementation specific if file attributes can be copied to the
1157 * new link. In other words, the {@code COPY_ATTRIBUTES} option may be
1158 * ignored when copying a symbolic link. </td>
1159 * </tr>
1160 * </table>
1161 *
1162 * <p> An implementation of this interface may support additional
1163 * implementation specific options.
1164 *
1165 * <p> Copying a file is not an atomic operation. If an {@link IOException}
1166 * is thrown then it possible that the target file is incomplete or some of
1167 * its file attributes have not been copied from the source file. When the
1168 * {@code REPLACE_EXISTING} option is specified and the target file exists,
1169 * then the target file is replaced. The check for the existence of the file
1170 * and the creation of the new file may not be atomic with respect to other
1171 * file system activities.
1172 *
1173 * <p> <b>Usage Example:</b>
1174 * Suppose we want to copy a file into a directory, giving it the same file
1175 * name as the source file:
1176 * <pre>
1177 * Path source = ...
1178 * Path newdir = ...
1179 * Files.copy(source, newdir.resolve(source.getFileName());
1180 * </pre>
1181 *
1182 * @param source
1183 * the path to the file to copy
1184 * @param target
1185 * the path to the target file (may be associated with a different
1186 * provider to the source path)
1187 * @param options
1188 * options specifying how the copy should be done
1189 *
1190 * @return the path to the target file
1191 *
1192 * @throws UnsupportedOperationException
1193 * if the array contains a copy option that is not supported
1194 * @throws FileAlreadyExistsException
1195 * if the target file exists but cannot be replaced because the
1196 * {@code REPLACE_EXISTING} option is not specified <i>(optional
1197 * specific exception)</i>
1198 * @throws DirectoryNotEmptyException
1199 * the {@code REPLACE_EXISTING} option is specified but the file
1200 * cannot be replaced because it is a non-empty directory
1201 * <i>(optional specific exception)</i>
1202 * @throws IOException
1203 * if an I/O error occurs
1204 * @throws SecurityException
1205 * In the case of the default provider, and a security manager is
1206 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1207 * method is invoked to check read access to the source file, the
1208 * {@link SecurityManager#checkWrite(String) checkWrite} is invoked
1209 * to check write access to the target file. If a symbolic link is
1210 * copied the security manager is invoked to check {@link
1211 * LinkPermission}{@code ("symbolic")}.
1212 */
1213 public static Path copy(Path source, Path target, CopyOption... options)
1214 throws IOException
1215 {
1216 FileSystemProvider provider = provider(source);
1217 if (provider(target) == provider) {
1218 // same provider
1219 provider.copy(source, target, options);
1220 } else {
1221 // different providers
1222 CopyMoveHelper.copyToForeignTarget(source, target, options);
1223 }
1224 return target;
1225 }
1226
1227 /**
1228 * Move or rename a file to a target file.
1229 *
1230 * <p> By default, this method attempts to move the file to the target
1231 * file, failing if the target file exists except if the source and
1232 * target are the {@link #isSameFile same} file, in which case this method
1233 * has no effect. If the file is a symbolic link then the symbolic link
1234 * itself, not the target of the link, is moved. This method may be
1235 * invoked to move an empty directory. In some implementations a directory
1236 * has entries for special files or links that are created when the
1237 * directory is created. In such implementations a directory is considered
1238 * empty when only the special entries exist. When invoked to move a
1239 * directory that is not empty then the directory is moved if it does not
1240 * require moving the entries in the directory. For example, renaming a
1241 * directory on the same {@link FileStore} will usually not require moving
1242 * the entries in the directory. When moving a directory requires that its
1243 * entries be moved then this method fails (by throwing an {@code
1244 * IOException}). To move a <i>file tree</i> may involve copying rather
1245 * than moving directories and this can be done using the {@link
1246 * #copy copy} method in conjunction with the {@link
1247 * #walkFileTree Files.walkFileTree} utility method.
1248 *
1249 * <p> The {@code options} parameter may include any of the following:
1250 *
1251 * <table border=1 cellpadding=5 summary="">
1252 * <tr> <th>Option</th> <th>Description</th> </tr>
1253 * <tr>
1254 * <td> {@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING} </td>
1255 * <td> If the target file exists, then the target file is replaced if it
1256 * is not a non-empty directory. If the target file exists and is a
1257 * symbolic link, then the symbolic link itself, not the target of
1258 * the link, is replaced. </td>
1259 * </tr>
1260 * <tr>
1261 * <td> {@link StandardCopyOption#ATOMIC_MOVE ATOMIC_MOVE} </td>
1262 * <td> The move is performed as an atomic file system operation and all
1263 * other options are ignored. If the target file exists then it is
1264 * implementation specific if the existing file is replaced or this method
1265 * fails by throwing an {@link IOException}. If the move cannot be
1266 * performed as an atomic file system operation then {@link
1267 * AtomicMoveNotSupportedException} is thrown. This can arise, for
1268 * example, when the target location is on a different {@code FileStore}
1269 * and would require that the file be copied, or target location is
1270 * associated with a different provider to this object. </td>
1271 * </table>
1272 *
1273 * <p> An implementation of this interface may support additional
1274 * implementation specific options.
1275 *
1276 * <p> Where the move requires that the file be copied then the {@link
1277 * BasicFileAttributes#lastModifiedTime last-modified-time} is copied to the
1278 * new file. An implementation may also attempt to copy other file
1279 * attributes but is not required to fail if the file attributes cannot be
1280 * copied. When the move is performed as a non-atomic operation, and a {@code
1281 * IOException} is thrown, then the state of the files is not defined. The
1282 * original file and the target file may both exist, the target file may be
1283 * incomplete or some of its file attributes may not been copied from the
1284 * original file.
1285 *
1286 * <p> <b>Usage Examples:</b>
1287 * Suppose we want to rename a file to "newname", keeping the file in the
1288 * same directory:
1289 * <pre>
1290 * Path source = ...
1291 * Files.move(source, source.resolveSibling("newname"));
1292 * </pre>
1293 * Alternatively, suppose we want to move a file to new directory, keeping
1294 * the same file name, and replacing any existing file of that name in the
1295 * directory:
1296 * <pre>
1297 * Path source = ...
1298 * Path newdir = ...
1299 * Files.move(source, newdir.resolve(source.getFileName()), REPLACE_EXISTING);
1300 * </pre>
1301 *
1302 * @param source
1303 * the path to the file to move
1304 * @param target
1305 * the path to the target file (may be associated with a different
1306 * provider to the source path)
1307 * @param options
1308 * options specifying how the move should be done
1309 *
1310 * @return the path to the target file
1311 *
1312 * @throws UnsupportedOperationException
1313 * if the array contains a copy option that is not supported
1314 * @throws FileAlreadyExistsException
1315 * if the target file exists but cannot be replaced because the
1316 * {@code REPLACE_EXISTING} option is not specified <i>(optional
1317 * specific exception)</i>
1318 * @throws DirectoryNotEmptyException
1319 * the {@code REPLACE_EXISTING} option is specified but the file
1320 * cannot be replaced because it is a non-empty directory
1321 * <i>(optional specific exception)</i>
1322 * @throws AtomicMoveNotSupportedException
1323 * if the options array contains the {@code ATOMIC_MOVE} option but
1324 * the file cannot be moved as an atomic file system operation.
1325 * @throws IOException
1326 * if an I/O error occurs
1327 * @throws SecurityException
1328 * In the case of the default provider, and a security manager is
1329 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
1330 * method is invoked to check write access to both the source and
1331 * target file.
1332 */
1333 public static Path move(Path source, Path target, CopyOption... options)
1334 throws IOException
1335 {
1336 FileSystemProvider provider = provider(source);
1337 if (provider(target) == provider) {
1338 // same provider
1339 provider.move(source, target, options);
1340 } else {
1341 // different providers
1342 CopyMoveHelper.moveToForeignTarget(source, target, options);
1343 }
1344 return target;
1345 }
1346
1347 // -- Miscellenous --
1348
1349 /**
1350 * Reads the target of a symbolic link <i>(optional operation)</i>.
1351 *
1352 * <p> If the file system supports <a href="package-summary.html#links">symbolic
1353 * links</a> then this method is used to read the target of the link, failing
1354 * if the file is not a symbolic link. The target of the link need not exist.
1355 * The returned {@code Path} object will be associated with the same file
1356 * system as {@code link}.
1357 *
1358 * @param link
1359 * the path to the symbolic link
1360 *
1361 * @return a {@code Path} object representing the target of the link
1362 *
1363 * @throws UnsupportedOperationException
1364 * if the implementation does not support symbolic links
1365 * @throws NotLinkException
1366 * if the target could otherwise not be read because the file
1367 * is not a symbolic link <i>(optional specific exception)</i>
1368 * @throws IOException
1369 * if an I/O error occurs
1370 * @throws SecurityException
1371 * In the case of the default provider, and a security manager
1372 * is installed, it checks that {@code FilePermission} has been
1373 * granted with the "{@code readlink}" action to read the link.
1374 */
1375 public static Path readSymbolicLink(Path link) throws IOException {
1376 return provider(link).readSymbolicLink(link);
1377 }
1378
1379 /**
1380 * Returns the {@link FileStore} representing the file store where a file
1381 * is located.
1382 *
1383 * <p> Once a reference to the {@code FileStore} is obtained it is
1384 * implementation specific if operations on the returned {@code FileStore},
1385 * or {@link FileStoreAttributeView} objects obtained from it, continue
1386 * to depend on the existence of the file. In particular the behavior is not
1387 * defined for the case that the file is deleted or moved to a different
1388 * file store.
1389 *
1390 * @param path
1391 * the path to the file
1392 *
1393 * @return the file store where the file is stored
1394 *
1395 * @throws IOException
1396 * if an I/O error occurs
1397 * @throws SecurityException
1398 * In the case of the default provider, and a security manager is
1399 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1400 * method is invoked to check read access to the file, and in
1401 * addition it checks {@link RuntimePermission}<tt>
1402 * ("getFileStoreAttributes")</tt>
1403 */
1404 public static FileStore getFileStore(Path path) throws IOException {
1405 return provider(path).getFileStore(path);
1406 }
1407
1408 /**
1409 * Tests if two paths locate the same file.
1410 *
1411 * <p> If both {@code Path} objects are {@link Path#equals(Object) equal}
1412 * then this method returns {@code true} without checking if the file exists.
1413 * If the two {@code Path} objects are associated with different providers
1414 * then this method returns {@code false}. Otherwise, this method checks if
1415 * both {@code Path} objects locate the same file, and depending on the
1416 * implementation, may require to open or access both files.
1417 *
1418 * <p> If the file system and files remain static, then this method implements
1419 * an equivalence relation for non-null {@code Paths}.
1420 * <ul>
1421 * <li>It is <i>reflexive</i>: for {@code Path} {@code f},
1422 * {@code isSameFile(f,f)} should return {@code true}.
1423 * <li>It is <i>symmetric</i>: for two {@code Paths} {@code f} and {@code g},
1424 * {@code isSameFile(f,g)} will equal {@code isSameFile(g,f)}.
1425 * <li>It is <i>transitive</i>: for three {@code Paths}
1426 * {@code f}, {@code g}, and {@code h}, if {@code isSameFile(f,g)} returns
1427 * {@code true} and {@code isSameFile(g,h)} returns {@code true}, then
1428 * {@code isSameFile(g,h)} will return return {@code true}.
1429 * </ul>
1430 *
1431 * @param path
1432 * one path to the file
1433 * @param path2
1434 * the other path
1435 *
1436 * @return {@code true} if, and only if, the two paths locate the same file
1437 *
1438 * @throws IOException
1439 * if an I/O error occurs
1440 * @throws SecurityException
1441 * In the case of the default provider, and a security manager is
1442 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1443 * method is invoked to check read access to both files.
1444 *
1445 * @see java.nio.file.attribute.BasicFileAttributes#fileKey
1446 */
1447 public static boolean isSameFile(Path path, Path path2) throws IOException {
1448 return provider(path).isSameFile(path, path2);
1449 }
1450
1451 /**
1452 * Tells whether or not a file is considered <em>hidden</em>. The exact
1453 * definition of hidden is platform or provider dependent. On UNIX for
1454 * example a file is considered to be hidden if its name begins with a
1455 * period character ('.'). On Windows a file is considered hidden if it
1456 * isn't a directory and the DOS {@link DosFileAttributes#isHidden hidden}
1457 * attribute is set.
1458 *
1459 * <p> Depending on the implementation this method may require to access
1460 * the file system to determine if the file is considered hidden.
1461 *
1462 * @param path
1463 * the path to the file to test
1464 *
1465 * @return {@code true} if the file is considered hidden
1466 *
1467 * @throws IOException
1468 * if an I/O error occurs
1469 * @throws SecurityException
1470 * In the case of the default provider, and a security manager is
1471 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1472 * method is invoked to check read access to the file.
1473 */
1474 public static boolean isHidden(Path path) throws IOException {
1475 return provider(path).isHidden(path);
1476 }
1477
1478 // lazy loading of default and installed file type detectors
1479 private static class FileTypeDetectors{
1480 static final FileTypeDetector defaultFileTypeDetector =
1481 sun.nio.fs.DefaultFileTypeDetector.create();
1482 static final List<FileTypeDetector> installeDetectors =
1483 loadInstalledDetectors();
1484
1485 // loads all installed file type detectors
1486 private static List<FileTypeDetector> loadInstalledDetectors() {
1487 return AccessController
1488 .doPrivileged(new PrivilegedAction<List<FileTypeDetector>>() {
1489 @Override public List<FileTypeDetector> run() {
1490 List<FileTypeDetector> list = new ArrayList<>();
1491 ServiceLoader<FileTypeDetector> loader = ServiceLoader
1492 .load(FileTypeDetector.class, ClassLoader.getSystemClassLoader());
1493 for (FileTypeDetector detector: loader) {
1494 list.add(detector);
1495 }
1496 return list;
1497 }});
1498 }
1499 }
1500
1501 /**
1502 * Probes the content type of a file.
1503 *
1504 * <p> This method uses the installed {@link FileTypeDetector} implementations
1505 * to probe the given file to determine its content type. Each file type
1506 * detector's {@link FileTypeDetector#probeContentType probeContentType} is
1507 * invoked, in turn, to probe the file type. If the file is recognized then
1508 * the content type is returned. If the file is not recognized by any of the
1509 * installed file type detectors then a system-default file type detector is
1510 * invoked to guess the content type.
1511 *
1512 * <p> A given invocation of the Java virtual machine maintains a system-wide
1513 * list of file type detectors. Installed file type detectors are loaded
1514 * using the service-provider loading facility defined by the {@link ServiceLoader}
1515 * class. Installed file type detectors are loaded using the system class
1516 * loader. If the system class loader cannot be found then the extension class
1517 * loader is used; If the extension class loader cannot be found then the
1518 * bootstrap class loader is used. File type detectors are typically installed
1519 * by placing them in a JAR file on the application class path or in the
1520 * extension directory, the JAR file contains a provider-configuration file
1521 * named {@code java.nio.file.spi.FileTypeDetector} in the resource directory
1522 * {@code META-INF/services}, and the file lists one or more fully-qualified
1523 * names of concrete subclass of {@code FileTypeDetector } that have a zero
1524 * argument constructor. If the process of locating or instantiating the
1525 * installed file type detectors fails then an unspecified error is thrown.
1526 * The ordering that installed providers are located is implementation
1527 * specific.
1528 *
1529 * <p> The return value of this method is the string form of the value of a
1530 * Multipurpose Internet Mail Extension (MIME) content type as
1531 * defined by <a href="http://www.ietf.org/rfc/rfc2045.txt"><i>RFC 2045:
1532 * Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet
1533 * Message Bodies</i></a>. The string is guaranteed to be parsable according
1534 * to the grammar in the RFC.
1535 *
1536 * @param path
1537 * the path to the file to probe
1538 *
1539 * @return The content type of the file, or {@code null} if the content
1540 * type cannot be determined
1541 *
1542 * @throws IOException
1543 * if an I/O error occurs
1544 * @throws SecurityException
1545 * If a security manager is installed and it denies an unspecified
1546 * permission required by a file type detector implementation.
1547 */
1548 public static String probeContentType(Path path)
1549 throws IOException
1550 {
1551 // try installed file type detectors
1552 for (FileTypeDetector detector: FileTypeDetectors.installeDetectors) {
1553 String result = detector.probeContentType(path);
1554 if (result != null)
1555 return result;
1556 }
1557
1558 // fallback to default
1559 return FileTypeDetectors.defaultFileTypeDetector.probeContentType(path);
1560 }
1561
1562 // -- File Attributes --
1563
1564 /**
1565 * Returns a file attribute view of a given type.
1566 *
1567 * <p> A file attribute view provides a read-only or updatable view of a
1568 * set of file attributes. This method is intended to be used where the file
1569 * attribute view defines type-safe methods to read or update the file
1570 * attributes. The {@code type} parameter is the type of the attribute view
1571 * required and the method returns an instance of that type if supported.
1572 * The {@link BasicFileAttributeView} type supports access to the basic
1573 * attributes of a file. Invoking this method to select a file attribute
1574 * view of that type will always return an instance of that class.
1575 *
1576 * <p> The {@code options} array may be used to indicate how symbolic links
1577 * are handled by the resulting file attribute view for the case that the
1578 * file is a symbolic link. By default, symbolic links are followed. If the
1579 * option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is present then
1580 * symbolic links are not followed. This option is ignored by implementations
1581 * that do not support symbolic links.
1582 *
1583 * <p> <b>Usage Example:</b>
1584 * Suppose we want read or set a file's ACL, if supported:
1585 * <pre>
1586 * Path path = ...
1587 * AclFileAttributeView view = Files.getFileAttributeView(path, AclFileAttributeView.class);
1588 * if (view != null) {
1589 * List<AclEntry> acl = view.getAcl();
1590 * :
1591 * }
1592 * </pre>
1593 *
1594 *
1595 * @param path
1596 * the path to the file
1597 * @param type
1598 * the {@code Class} object corresponding to the file attribute view
1599 * @param options
1600 * options indicating how symbolic links are handled
1601 *
1602 * @return a file attribute view of the specified type, or {@code null} if
1603 * the attribute view type is not available
1604 */
1605 public static <V extends FileAttributeView> V getFileAttributeView(Path path,
1606 Class<V> type,
1607 LinkOption... options)
1608 {
1609 return provider(path).getFileAttributeView(path, type, options);
1610 }
1611
1612 /**
1613 * Reads a file's attributes as a bulk operation.
1614 *
1615 * <p> The {@code type} parameter is the type of the attributes required
1616 * and this method returns an instance of that type if supported. All
1617 * implementations support a basic set of file attributes and so invoking
1618 * this method with a {@code type} parameter of {@code
1619 * BasicFileAttributes.class} will not throw {@code
1620 * UnsupportedOperationException}.
1621 *
1622 * <p> The {@code options} array may be used to indicate how symbolic links
1623 * are handled for the case that the file is a symbolic link. By default,
1624 * symbolic links are followed and the file attribute of the final target
1625 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1626 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1627 *
1628 * <p> It is implementation specific if all file attributes are read as an
1629 * atomic operation with respect to other file system operations.
1630 *
1631 * <p> <b>Usage Example:</b>
1632 * Suppose we want to read a file's attributes in bulk:
1633 * <pre>
1634 * Path path = ...
1635 * BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class);
1636 * </pre>
1637 * Alternatively, suppose we want to read file's POSIX attributes without
1638 * following symbolic links:
1639 * <pre>
1640 * PosixFileAttributes attrs = Files.readAttributes(path, PosixFileAttributes.class, NOFOLLOW_LINKS);
1641 * </pre>
1642 *
1643 * @param path
1644 * the path to the file
1645 * @param type
1646 * the {@code Class} of the file attributes required
1647 * to read
1648 * @param options
1649 * options indicating how symbolic links are handled
1650 *
1651 * @return the file attributes
1652 *
1653 * @throws UnsupportedOperationException
1654 * if an attributes of the given type are not supported
1655 * @throws IOException
1656 * if an I/O error occurs
1657 * @throws SecurityException
1658 * In the case of the default provider, a security manager is
1659 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1660 * method is invoked to check read access to the file. If this
1661 * method is invoked to read security sensitive attributes then the
1662 * security manager may be invoke to check for additional permissions.
1663 */
1664 public static <A extends BasicFileAttributes> A readAttributes(Path path,
1665 Class<A> type,
1666 LinkOption... options)
1667 throws IOException
1668 {
1669 return provider(path).readAttributes(path, type, options);
1670 }
1671
1672 /**
1673 * Sets the value of a file attribute.
1674 *
1675 * <p> The {@code attribute} parameter identifies the attribute to be set
1676 * and takes the form:
1677 * <blockquote>
1678 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
1679 * </blockquote>
1680 * where square brackets [...] delineate an optional component and the
1681 * character {@code ':'} stands for itself.
1682 *
1683 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1684 * FileAttributeView} that identifies a set of file attributes. If not
1685 * specified then it defaults to {@code "basic"}, the name of the file
1686 * attribute view that identifies the basic set of file attributes common to
1687 * many file systems. <i>attribute-name</i> is the name of the attribute
1688 * within the set.
1689 *
1690 * <p> The {@code options} array may be used to indicate how symbolic links
1691 * are handled for the case that the file is a symbolic link. By default,
1692 * symbolic links are followed and the file attribute of the final target
1693 * of the link is set. If the option {@link LinkOption#NOFOLLOW_LINKS
1694 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1695 *
1696 * <p> <b>Usage Example:</b>
1697 * Suppose we want to set the DOS "hidden" attribute:
1698 * <pre>
1699 * Path path = ...
1700 * Files.setAttribute(path, "dos:hidden", true);
1701 * </pre>
1702 *
1703 * @param path
1704 * the path to the file
1705 * @param attribute
1706 * the attribute to set
1707 * @param value
1708 * the attribute value
1709 * @param options
1710 * options indicating how symbolic links are handled
1711 *
1712 * @return the {@code path} parameter
1713 *
1714 * @throws UnsupportedOperationException
1715 * if the attribute view is not available or it does not support
1716 * updating the attribute
1717 * @throws IllegalArgumentException
1718 * if the attribute value is of the correct type but has an
1719 * inappropriate value
1720 * @throws ClassCastException
1721 * if the attribute value is not of the expected type or is a
1722 * collection containing elements that are not of the expected
1723 * type
1724 * @throws IOException
1725 * if an I/O error occurs
1726 * @throws SecurityException
1727 * In the case of the default provider, and a security manager is
1728 * installed, its {@link SecurityManager#checkWrite(String) checkWrite}
1729 * method denies write access to the file. If this method is invoked
1730 * to set security sensitive attributes then the security manager
1731 * may be invoked to check for additional permissions.
1732 */
1733 public static Path setAttribute(Path path, String attribute, Object value,
1734 LinkOption... options)
1735 throws IOException
1736 {
1737 provider(path).setAttribute(path, attribute, value, options);
1738 return path;
1739 }
1740
1741 /**
1742 * Reads the value of a file attribute.
1743 *
1744 * <p> The {@code attribute} parameter identifies the attribute to be read
1745 * and takes the form:
1746 * <blockquote>
1747 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
1748 * </blockquote>
1749 * where square brackets [...] delineate an optional component and the
1750 * character {@code ':'} stands for itself.
1751 *
1752 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1753 * FileAttributeView} that identifies a set of file attributes. If not
1754 * specified then it defaults to {@code "basic"}, the name of the file
1755 * attribute view that identifies the basic set of file attributes common to
1756 * many file systems. <i>attribute-name</i> is the name of the attribute.
1757 *
1758 * <p> The {@code options} array may be used to indicate how symbolic links
1759 * are handled for the case that the file is a symbolic link. By default,
1760 * symbolic links are followed and the file attribute of the final target
1761 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1762 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1763 *
1764 * <p> <b>Usage Example:</b>
1765 * Suppose we require the user ID of the file owner on a system that
1766 * supports a "{@code unix}" view:
1767 * <pre>
1768 * Path path = ...
1769 * int uid = (Integer)Files.getAttribute(path, "unix:uid");
1770 * </pre>
1771 *
1772 * @param path
1773 * the path to the file
1774 * @param attribute
1775 * the attribute to read
1776 * @param options
1777 * options indicating how symbolic links are handled
1778 *
1779 * @return the attribute value or {@code null} if the attribute view
1780 * is not available or it does not support reading the attribute
1781 *
1782 * @throws IOException
1783 * if an I/O error occurs
1784 * @throws SecurityException
1785 * In the case of the default provider, and a security manager is
1786 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1787 * method denies read access to the file. If this method is invoked
1788 * to read security sensitive attributes then the security manager
1789 * may be invoked to check for additional permissions.
1790 */
1791 public static Object getAttribute(Path path, String attribute,
1792 LinkOption... options)
1793 throws IOException
1794 {
1795 // only one attribute should be read
1796 if (attribute.indexOf('*') >= 0 || attribute.indexOf(',') >= 0)
1797 return null;
1798 Map<String,Object> map = readAttributes(path, attribute, options);
1799 String name;
1800 int pos = attribute.indexOf(':');
1801 if (pos == -1) {
1802 name = attribute;
1803 } else {
1804 name = (pos == attribute.length()) ? "" : attribute.substring(pos+1);
1805 }
1806 return map.get(name);
1807 }
1808
1809 /**
1810 * Reads a set of file attributes as a bulk operation.
1811 *
1812 * <p> The {@code attributes} parameter identifies the attributes to be read
1813 * and takes the form:
1814 * <blockquote>
1815 * [<i>view-name</i><b>:</b>]<i>attribute-list</i>
1816 * </blockquote>
1817 * where square brackets [...] delineate an optional component and the
1818 * character {@code ':'} stands for itself.
1819 *
1820 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1821 * FileAttributeView} that identifies a set of file attributes. If not
1822 * specified then it defaults to {@code "basic"}, the name of the file
1823 * attribute view that identifies the basic set of file attributes common to
1824 * many file systems.
1825 *
1826 * <p> The <i>attribute-list</i> component is a comma separated list of
1827 * zero or more names of attributes to read. If the list contains the value
1828 * {@code "*"} then all attributes are read. Attributes that are not supported
1829 * are ignored and will not be present in the returned map. It is
1830 * implementation specific if all attributes are read as an atomic operation
1831 * with respect to other file system operations.
1832 *
1833 * <p> The following examples demonstrate possible values for the {@code
1834 * attributes} parameter:
1835 *
1836 * <blockquote>
1837 * <table border="0">
1838 * <tr>
1839 * <td> {@code "*"} </td>
1840 * <td> Read all {@link BasicFileAttributes basic-file-attributes}. </td>
1841 * </tr>
1842 * <tr>
1843 * <td> {@code "size,lastModifiedTime,lastAccessTime"} </td>
1844 * <td> Reads the file size, last modified time, and last access time
1845 * attributes. </td>
1846 * </tr>
1847 * <tr>
1848 * <td> {@code "posix:*"} </td>
1849 * <td> Read all {@link PosixFileAttributes POSIX-file-attributes}. </td>
1850 * </tr>
1851 * <tr>
1852 * <td> {@code "posix:permissions,owner,size"} </td>
1853 * <td> Reads the POSX file permissions, owner, and file size. </td>
1854 * </tr>
1855 * </table>
1856 * </blockquote>
1857 *
1858 * <p> The {@code options} array may be used to indicate how symbolic links
1859 * are handled for the case that the file is a symbolic link. By default,
1860 * symbolic links are followed and the file attribute of the final target
1861 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1862 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1863 *
1864 * @param path
1865 * the path to the file
1866 * @param attributes
1867 * the attributes to read
1868 * @param options
1869 * options indicating how symbolic links are handled
1870 *
1871 * @return a map of the attributes returned; may be empty. The map's keys
1872 * are the attribute names, its values are the attribute values
1873 *
1874 * @throws IOException
1875 * if an I/O error occurs
1876 * @throws SecurityException
1877 * In the case of the default provider, and a security manager is
1878 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1879 * method denies read access to the file. If this method is invoked
1880 * to read security sensitive attributes then the security manager
1881 * may be invoke to check for additional permissions.
1882 */
1883 public static Map<String,Object> readAttributes(Path path, String attributes,
1884 LinkOption... options)
1885 throws IOException
1886 {
1887 return provider(path).readAttributes(path, attributes, options);
1888 }
1889
1890 /**
1891 * Returns a file's POSIX file permissions.
1892 *
1893 * <p> The {@code path} parameter is associated with a {@code FileSystem}
1894 * that supports the {@link PosixFileAttributeView}. This attribute view
1895 * provides access to file attributes commonly associated with files on file
1896 * systems used by operating systems that implement the Portable Operating
1897 * System Interface (POSIX) family of standards.
1898 *
1899 * <p> The {@code options} array may be used to indicate how symbolic links
1900 * are handled for the case that the file is a symbolic link. By default,
1901 * symbolic links are followed and the file attribute of the final target
1902 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1903 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1904 *
1905 * @param path
1906 * the path to the file
1907 * @param options
1908 * options indicating how symbolic links are handled
1909 *
1910 * @return the file permissions
1911 *
1912 * @throws UnsupportedOperationException
1913 * if the associated file system does not support the {@code
1914 * PosixFileAttributeView}
1915 * @throws IOException
1916 * if an I/O error occurs
1917 * @throws SecurityException
1918 * In the case of the default provider, a security manager is
1919 * installed, and it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
1920 * or its {@link SecurityManager#checkRead(String) checkRead} method
1921 * denies read access to the file.
1922 */
1923 public static Set<PosixFilePermission> getPosixFilePermissions(Path path,
1924 LinkOption... options)
1925 throws IOException
1926 {
1927 return readAttributes(path, PosixFileAttributes.class, options).permissions();
1928 }
1929
1930 /**
1931 * Sets a file's POSIX permissions.
1932 *
1933 * <p> The {@code path} parameter is associated with a {@code FileSystem}
1934 * that supports the {@link PosixFileAttributeView}. This attribute view
1935 * provides access to file attributes commonly associated with files on file
1936 * systems used by operating systems that implement the Portable Operating
1937 * System Interface (POSIX) family of standards.
1938 *
1939 * @param path
1940 * A file reference that locates the file
1941 * @param perms
1942 * The new set of permissions
1943 *
1944 * @throws UnsupportedOperationException
1945 * if the associated file system does not support the {@code
1946 * PosixFileAttributeView}
1947 * @throws ClassCastException
1948 * if the sets contains elements that are not of type {@code
1949 * PosixFilePermission}
1950 * @throws IOException
1951 * if an I/O error occurs
1952 * @throws SecurityException
1953 * In the case of the default provider, and a security manager is
1954 * installed, it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
1955 * or its {@link SecurityManager#checkWrite(String) checkWrite}
1956 * method denies write access to the file.
1957 */
1958 public static Path setPosixFilePermissions(Path path,
1959 Set<PosixFilePermission> perms)
1960 throws IOException
1961 {
1962 PosixFileAttributeView view =
1963 getFileAttributeView(path, PosixFileAttributeView.class);
1964 if (view == null)
1965 throw new UnsupportedOperationException();
1966 view.setPermissions(perms);
1967 return path;
1968 }
1969
1970 /**
1971 * Returns the owner of a file.
1972 *
1973 * <p> The {@code path} parameter is associated with a file system that
1974 * supports {@link FileOwnerAttributeView}. This file attribute view provides
1975 * access to a file attribute that is the owner of the file.
1976 *
1977 * @param path
1978 * A file reference that locates the file
1979 * @param options
1980 * options indicating how symbolic links are handled
1981 *
1982 * @return A user principal representing the owner of the file
1983 *
1984 * @throws UnsupportedOperationException
1985 * if the associated file system does not support the {@code
1986 * FileOwnerAttributeView}
1987 * @throws IOException
1988 * if an I/O error occurs
1989 * @throws SecurityException
1990 * In the case of the default provider, and a security manager is
1991 * installed, it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
1992 * or its {@link SecurityManager#checkRead(String) checkRead} method
1993 * denies read access to the file.
1994 */
1995 public static UserPrincipal getOwner(Path path, LinkOption... options) throws IOException {
1996 FileOwnerAttributeView view =
1997 getFileAttributeView(path, FileOwnerAttributeView.class, options);
1998 if (view == null)
1999 throw new UnsupportedOperationException();
2000 return view.getOwner();
2001 }
2002
2003 /**
2004 * Updates the file owner.
2005 *
2006 * <p> The {@code path} parameter is associated with a file system that
2007 * supports {@link FileOwnerAttributeView}. This file attribute view provides
2008 * access to a file attribute that is the owner of the file.
2009 *
2010 * <p> <b>Usage Example:</b>
2011 * Suppose we want to make "joe" the owner of a file:
2012 * <pre>
2013 * Path path = ...
2014 * UserPrincipalLookupService lookupService =
2015 * provider(path).getUserPrincipalLookupService();
2016 * UserPrincipal joe = lookupService.lookupPrincipalByName("joe");
2017 * Files.setOwner(path, joe);
2018 * </pre>
2019 *
2020 * @param path
2021 * A file reference that locates the file
2022 * @param owner
2023 * The new file owner
2024 *
2025 * @throws UnsupportedOperationException
2026 * if the associated file system does not support the {@code
2027 * FileOwnerAttributeView}
2028 * @throws IOException
2029 * if an I/O error occurs
2030 * @throws SecurityException
2031 * In the case of the default provider, and a security manager is
2032 * installed, it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
2033 * or its {@link SecurityManager#checkWrite(String) checkWrite}
2034 * method denies write access to the file.
2035 *
2036 * @see FileSystem#getUserPrincipalLookupService
2037 * @see java.nio.file.attribute.UserPrincipalLookupService
2038 */
2039 public static Path setOwner(Path path, UserPrincipal owner)
2040 throws IOException
2041 {
2042 FileOwnerAttributeView view =
2043 getFileAttributeView(path, FileOwnerAttributeView.class);
2044 if (view == null)
2045 throw new UnsupportedOperationException();
2046 view.setOwner(owner);
2047 return path;
2048 }
2049
2050 /**
2051 * Tests whether a file is a symbolic link.
2052 *
2053 * <p> Where is it required to distinguish an I/O exception from the case
2054 * that the file is not a symbolic link then the file attributes can be
2055 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2056 * readAttributes} method and the file type tested with the {@link
2057 * BasicFileAttributes#isSymbolicLink} method.
2058 *
2059 * @return {@code true} if the file is a symbolic link; {@code false} if
2060 * the file does not exist, is not a symbolic link, or it cannot
2061 * be determined if the file is symbolic link or not.
2062 *
2063 * @throws SecurityException
2064 * In the case of the default provider, and a security manager is
2065 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2066 * method denies read access to the file.
2067 */
2068 public static boolean isSymbolicLink(Path path) {
2069 try {
2070 return readAttributes(path,
2071 BasicFileAttributes.class,
2072 LinkOption.NOFOLLOW_LINKS).isSymbolicLink();
2073 } catch (IOException ioe) {
2074 return false;
2075 }
2076 }
2077
2078 /**
2079 * Tests whether a file is a directory.
2080 *
2081 * <p> The {@code options} array may be used to indicate how symbolic links
2082 * are handled for the case that the file is a symbolic link. By default,
2083 * symbolic links are followed and the file attribute of the final target
2084 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2085 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2086 *
2087 * <p> Where is it required to distinguish an I/O exception from the case
2088 * that the file is not a directory then the file attributes can be
2089 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2090 * readAttributes} method and the file type tested with the {@link
2091 * BasicFileAttributes#isDirectory} method.
2092 *
2093 * @param path
2094 * the path to the file to test
2095 * @param options
2096 * options indicating how symbolic links are handled
2097 *
2098 * @return {@code true} if the file is a directory; {@code false} if
2099 * the file does not exist, is not a directory, or it cannot
2100 * be determined if the file is directory or not.
2101 *
2102 * @throws SecurityException
2103 * In the case of the default provider, and a security manager is
2104 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2105 * method denies read access to the file.
2106 */
2107 public static boolean isDirectory(Path path, LinkOption... options) {
2108 try {
2109 return readAttributes(path, BasicFileAttributes.class, options).isDirectory();
2110 } catch (IOException ioe) {
2111 return false;
2112 }
2113 }
2114
2115 /**
2116 * Tests whether a file is a regular file with opaque content.
2117 *
2118 * <p> The {@code options} array may be used to indicate how symbolic links
2119 * are handled for the case that the file is a symbolic link. By default,
2120 * symbolic links are followed and the file attribute of the final target
2121 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2122 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2123 *
2124 * <p> Where is it required to distinguish an I/O exception from the case
2125 * that the file is not a regular file then the file attributes can be
2126 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2127 * readAttributes} method and the file type tested with the {@link
2128 * BasicFileAttributes#isRegularFile} method.
2129 *
2130 * @param path
2131 * the path to the file
2132 * @param options
2133 * options indicating how symbolic links are handled
2134 *
2135 * @return {@code true} if the file is a regular file; {@code false} if
2136 * the file does not exist, is not a direcregular filetory, or it
2137 * cannot be determined if the file is regular file or not.
2138 *
2139 * @throws SecurityException
2140 * In the case of the default provider, and a security manager is
2141 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2142 * method denies read access to the file.
2143 */
2144 public static boolean isRegularFile(Path path, LinkOption... options) {
2145 try {
2146 return readAttributes(path, BasicFileAttributes.class, options).isRegularFile();
2147 } catch (IOException ioe) {
2148 return false;
2149 }
2150 }
2151
2152 /**
2153 * Returns a file's last modified time.
2154 *
2155 * <p> The {@code options} array may be used to indicate how symbolic links
2156 * are handled for the case that the file is a symbolic link. By default,
2157 * symbolic links are followed and the file attribute of the final target
2158 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2159 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2160 *
2161 * @param path
2162 * the path to the file
2163 * @param options
2164 * options indicating how symbolic links are handled
2165 *
2166 * @return a {@code FileTime} representing the time the file was last
2167 * modified, or an implementation specific default when a time
2168 * stamp to indicate the time of last modification is not supported
2169 * by the file system
2170 *
2171 * @throws IOException
2172 * if an I/O error occurs
2173 * @throws SecurityException
2174 * In the case of the default provider, and a security manager is
2175 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2176 * method denies read access to the file.
2177 *
2178 * @see BasicFileAttributes#lastModifiedTime
2179 */
2180 public static FileTime getLastModifiedTime(Path path, LinkOption... options)
2181 throws IOException
2182 {
2183 return readAttributes(path, BasicFileAttributes.class, options).lastModifiedTime();
2184 }
2185
2186 /**
2187 * Updates a file's last modified time attribute. The file time is converted
2188 * to the epoch and precision supported by the file system. Converting from
2189 * finer to coarser granularities result in precision loss. The behavior of
2190 * this method when attempting to set the last modified time when it is not
2191 * supported by the file system or is outside the range supported by the
2192 * underlying file store is not defined. It may or not fail by throwing an
2193 * {@code IOException}.
2194 *
2195 * <p> <b>Usage Example:</b>
2196 * Suppose we want to set the last modified time to the current time:
2197 * <pre>
2198 * Path path = ...
2199 * FileTime now = FileTime.fromMillis(System.currentTimeMillis());
2200 * Files.setLastModifiedTime(path, now);
2201 * </pre>
2202 *
2203 * @param path
2204 * the path to the file
2205 * @param time
2206 * the new last modified time
2207 *
2208 * @return the file
2209 *
2210 * @throws IOException
2211 * if an I/O error occurs
2212 * @throws SecurityException
2213 * In the case of the default provider, the security manager's {@link
2214 * SecurityManager#checkWrite(String) checkWrite} method is invoked
2215 * to check write access to file
2216 *
2217 * @see BasicFileAttributeView#setTimes
2218 */
2219 public static Path setLastModifiedTime(Path path, FileTime time)
2220 throws IOException
2221 {
2222 getFileAttributeView(path, BasicFileAttributeView.class)
2223 .setTimes(time, null, null);
2224 return path;
2225 }
2226
2227 /**
2228 * Returns the size of a file (in bytes). The size may differ from the
2229 * actual size on the file system due to compression, support for sparse
2230 * files, or other reasons. The size of files that are not {@link
2231 * #isRegularFile regular} files is implementation specific and
2232 * therefore unspecified.
2233 *
2234 * @param path
2235 * the path to the file
2236 *
2237 * @return the file size, in bytes
2238 *
2239 * @throws IOException
2240 * if an I/O error occurs
2241 * @throws SecurityException
2242 * In the case of the default provider, and a security manager is
2243 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2244 * method denies read access to the file.
2245 *
2246 * @see BasicFileAttributes#size
2247 */
2248 public static long size(Path path) throws IOException {
2249 return readAttributes(path, BasicFileAttributes.class).size();
2250 }
2251
2252 // -- Accessibility --
2253
2254 /**
2255 * Returns {@code false} if NOFOLLOW_LINKS is present.
2256 */
2257 private static boolean followLinks(LinkOption... options) {
2258 boolean followLinks = true;
2259 for (LinkOption opt: options) {
2260 if (opt == LinkOption.NOFOLLOW_LINKS) {
2261 followLinks = false;
2262 continue;
2263 }
2264 if (opt == null)
2265 throw new NullPointerException();
2266 throw new AssertionError("Should not get here");
2267 }
2268 return followLinks;
2269 }
2270
2271 /**
2272 * Tests whether a file exists.
2273 *
2274 * <p> The {@code options} parameter may be used to indicate how symbolic links
2275 * are handled for the case that the file is a symbolic link. By default,
2276 * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
2277 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2278 *
2279 * <p> Note that the result of this method is immediately outdated. If this
2280 * method indicates the file exists then there is no guarantee that a
2281 * subsequence access will succeed. Care should be taken when using this
2282 * method in security sensitive applications.
2283 *
2284 * @param path
2285 * the path to the file to test
2286 * @param options
2287 * options indicating how symbolic links are handled
2288 * .
2289 * @return {@code true} if the file exists; {@code false} if the file does
2290 * not exist or its existence cannot be determined.
2291 *
2292 * @throws SecurityException
2293 * In the case of the default provider, the {@link
2294 * SecurityManager#checkRead(String)} is invoked to check
2295 * read access to the file.
2296 *
2297 * @see #notExists
2298 */
2299 public static boolean exists(Path path, LinkOption... options) {
2300 try {
2301 if (followLinks(options)) {
2302 provider(path).checkAccess(path);
2303 } else {
2304 // attempt to read attributes without following links
2305 readAttributes(path, BasicFileAttributes.class,
2306 LinkOption.NOFOLLOW_LINKS);
2307 }
2308 // file exists
2309 return true;
2310 } catch (IOException x) {
2311 // does not exist or unable to determine if file exists
2312 return false;
2313 }
2314
2315 }
2316
2317 /**
2318 * Tests whether the file located by this path does not exist. This method
2319 * is intended for cases where it is required to take action when it can be
2320 * confirmed that a file does not exist.
2321 *
2322 * <p> The {@code options} parameter may be used to indicate how symbolic links
2323 * are handled for the case that the file is a symbolic link. By default,
2324 * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
2325 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2326 *
2327 * <p> Note that this method is not the complement of the {@link #exists
2328 * exists} method. Where it is not possible to determine if a file exists
2329 * or not then both methods return {@code false}. As with the {@code exists}
2330 * method, the result of this method is immediately outdated. If this
2331 * method indicates the file does exist then there is no guarantee that a
2332 * subsequence attempt to create the file will succeed. Care should be taken
2333 * when using this method in security sensitive applications.
2334 *
2335 * @param path
2336 * the path to the file to test
2337 * @param options
2338 * options indicating how symbolic links are handled
2339 *
2340 * @return {@code true} if the file does not exist; {@code false} if the
2341 * file exists or its existence cannot be determined
2342 *
2343 * @throws SecurityException
2344 * In the case of the default provider, the {@link
2345 * SecurityManager#checkRead(String)} is invoked to check
2346 * read access to the file.
2347 */
2348 public static boolean notExists(Path path, LinkOption... options) {
2349 try {
2350 if (followLinks(options)) {
2351 provider(path).checkAccess(path);
2352 } else {
2353 // attempt to read attributes without following links
2354 readAttributes(path, BasicFileAttributes.class,
2355 LinkOption.NOFOLLOW_LINKS);
2356 }
2357 // file exists
2358 return false;
2359 } catch (NoSuchFileException x) {
2360 // file confirmed not to exist
2361 return true;
2362 } catch (IOException x) {
2363 return false;
2364 }
2365 }
2366
2367 /**
2368 * Used by isReadbale, isWritable, isExecutable to test access to a file.
2369 */
2370 private static boolean isAccessible(Path path, AccessMode... modes) {
2371 try {
2372 provider(path).checkAccess(path, modes);
2373 return true;
2374 } catch (IOException x) {
2375 return false;
2376 }
2377 }
2378
2379 /**
2380 * Tests whether a file is readable. This method checks that a file exists
2381 * and that this Java virtual machine has appropriate privileges that would
2382 * allow it open the file for reading. Depending on the implementation, this
2383 * method may require to read file permissions, access control lists, or
2384 * other file attributes in order to check the effective access to the file.
2385 * Consequently, this method may not be atomic with respect to other file
2386 * system operations.
2387 *
2388 * <p> Note that the result of this method is immediately outdated, there is
2389 * no guarantee that a subsequent attempt to open the file for reading will
2390 * succeed (or even that it will access the same file). Care should be taken
2391 * when using this method in security sensitive applications.
2392 *
2393 * @param path
2394 * the path to the file to check
2395 *
2396 * @return {@code true} if the file exists and is readable; {@code false}
2397 * if the file does not exist, read access would be denied because
2398 * the Java virtual machine has insufficient privileges, or access
2399 * cannot be determined
2400 *
2401 * @throws SecurityException
2402 * In the case of the default provider, and a security manager is
2403 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2404 * is invoked to check read access to the file.
2405 */
2406 public static boolean isReadable(Path path) {
2407 return isAccessible(path, AccessMode.READ);
2408 }
2409
2410 /**
2411 * Tests whether a file is writable. This method checks that a file exists
2412 * and that this Java virtual machine has appropriate privileges that would
2413 * allow it open the file for writing. Depending on the implementation, this
2414 * method may require to read file permissions, access control lists, or
2415 * other file attributes in order to check the effective access to the file.
2416 * Consequently, this method may not be atomic with respect to other file
2417 * system operations.
2418 *
2419 * <p> Note that result of this method is immediately outdated, there is no
2420 * guarantee that a subsequent attempt to open the file for writing will
2421 * succeed (or even that it will access the same file). Care should be taken
2422 * when using this method in security sensitive applications.
2423 *
2424 * @param path
2425 * the path to the file to check
2426 *
2427 * @return {@code true} if the file exists and is writable; {@code false}
2428 * if the file does not exist, write access would be denied because
2429 * the Java virtual machine has insufficient privileges, or access
2430 * cannot be determined
2431 *
2432 * @throws SecurityException
2433 * In the case of the default provider, and a security manager is
2434 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2435 * is invoked to check write access to the file.
2436 */
2437 public static boolean isWritable(Path path) {
2438 return isAccessible(path, AccessMode.WRITE);
2439 }
2440
2441 /**
2442 * Tests whether a file is executable. This method checks that a file exists
2443 * and that this Java virtual machine has appropriate privileges to {@link
2444 * Runtime#exec execute} the file. The semantics may differ when checking
2445 * access to a directory. For example, on UNIX systems, checking for
2446 * execute access checks that the Java virtual machine has permission to
2447 * search the directory in order to access file or subdirectories.
2448 *
2449 * <p> Depending on the implementation, this method may require to read file
2450 * permissions, access control lists, or other file attributes in order to
2451 * check the effective access to the file. Consequently, this method may not
2452 * be atomic with respect to other file system operations.
2453 *
2454 * <p> Note that the result of this method is immediately outdated, there is
2455 * no guarantee that a subsequent attempt to execute the file will succeed
2456 * (or even that it will access the same file). Care should be taken when
2457 * using this method in security sensitive applications.
2458 *
2459 * @param path
2460 * the path to the file to check
2461 *
2462 * @return {@code true} if the file exists and is executable; {@code false}
2463 * if the file does not exist, execute access would be denied because
2464 * the Java virtual machine has insufficient privileges, or access
2465 * cannot be determined
2466 *
2467 * @throws SecurityException
2468 * In the case of the default provider, and a security manager is
2469 * installed, the {@link SecurityManager#checkExec(String)
2470 * checkExec} is invoked to check execute access to the file.
2471 */
2472 public static boolean isExecutable(Path path) {
2473 return isAccessible(path, AccessMode.EXECUTE);
2474 }
2475
2476 // -- Recursive operations --
2477
2478 /**
2479 * Walks a file tree.
2480 *
2481 * <p> This method walks a file tree rooted at a given starting file. The
2482 * file tree traversal is <em>depth-first</em> with the given {@link
2483 * FileVisitor} invoked for each file encountered. File tree traversal
2484 * completes when all accessible files in the tree have been visited, or a
2485 * visit method returns a result of {@link FileVisitResult#TERMINATE
2486 * TERMINATE}. Where a visit method terminates due an {@code IOException},
2487 * an uncaught error, or runtime exception, then the traversal is terminated
2488 * and the error or exception is propagated to the caller of this method.
2489 *
2490 * <p> For each file encountered this method attempts to read its {@link
2491 * java.nio.file.attribute.BasicFileAttributes}. If the file is not a
2492 * directory then the {@link FileVisitor#visitFile visitFile} method is
2493 * invoked with the file attributes. If the file attributes cannot be read,
2494 * due to an I/O exception, then the {@link FileVisitor#visitFileFailed
2495 * visitFileFailed} method is invoked with the I/O exception.
2496 *
2497 * <p> Where the file is a directory, and the directory could not be opened,
2498 * then the {@code visitFileFailed} method is invoked with the I/O exception,
2499 * after which, the file tree walk continues, by default, at the next
2500 * <em>sibling</em> of the directory.
2501 *
2502 * <p> Where the directory is opened successfully, then the entries in the
2503 * directory, and their <em>descendants</em> are visited. When all entries
2504 * have been visited, or an I/O error occurs during iteration of the
2505 * directory, then the directory is closed and the visitor's {@link
2506 * FileVisitor#postVisitDirectory postVisitDirectory} method is invoked.
2507 * The file tree walk then continues, by default, at the next <em>sibling</em>
2508 * of the directory.
2509 *
2510 * <p> By default, symbolic links are not automatically followed by this
2511 * method. If the {@code options} parameter contains the {@link
2512 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then symbolic links are
2513 * followed. When following links, and the attributes of the target cannot
2514 * be read, then this method attempts to get the {@code BasicFileAttributes}
2515 * of the link. If they can be read then the {@code visitFile} method is
2516 * invoked with the attributes of the link (otherwise the {@code visitFileFailed}
2517 * method is invoked as specified above).
2518 *
2519 * <p> If the {@code options} parameter contains the {@link
2520 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then this method keeps
2521 * track of directories visited so that cycles can be detected. A cycle
2522 * arises when there is an entry in a directory that is an ancestor of the
2523 * directory. Cycle detection is done by recording the {@link
2524 * java.nio.file.attribute.BasicFileAttributes#fileKey file-key} of directories,
2525 * or if file keys are not available, by invoking the {@link #isSameFile
2526 * isSameFile} method to test if a directory is the same file as an
2527 * ancestor. When a cycle is detected it is treated as an I/O error, and the
2528 * {@link FileVisitor#visitFileFailed visitFileFailed} method is invoked with
2529 * an instance of {@link FileSystemLoopException}.
2530 *
2531 * <p> The {@code maxDepth} parameter is the maximum number of levels of
2532 * directories to visit. A value of {@code 0} means that only the starting
2533 * file is visited, unless denied by the security manager. A value of
2534 * {@link Integer#MAX_VALUE MAX_VALUE} may be used to indicate that all
2535 * levels should be visited. The {@code visitFile} method is invoked for all
2536 * files, including directories, encountered at {@code maxDepth}, unless the
2537 * basic file attributes cannot be read, in which case the {@code
2538 * visitFileFailed} method is invoked.
2539 *
2540 * <p> If a visitor returns a result of {@code null} then {@code
2541 * NullPointerException} is thrown.
2542 *
2543 * <p> When a security manager is installed and it denies access to a file
2544 * (or directory), then it is ignored and the visitor is not invoked for
2545 * that file (or directory).
2546 *
2547 * @param start
2548 * the starting file
2549 * @param options
2550 * options to configure the traversal
2551 * @param maxDepth
2552 * the maximum number of directory levels to visit
2553 * @param visitor
2554 * the file visitor to invoke for each file
2555 *
2556 * @return the starting file
2557 *
2558 * @throws IllegalArgumentException
2559 * if the {@code maxDepth} parameter is negative
2560 * @throws SecurityException
2561 * If the security manager denies access to the starting file.
2562 * In the case of the default provider, the {@link
2563 * SecurityManager#checkRead(String) checkRead} method is invoked
2564 * to check read access to the directory.
2565 * @throws IOException
2566 * if an I/O error is thrown by a visitor method
2567 */
2568 public static Path walkFileTree(Path start,
2569 Set<FileVisitOption> options,
2570 int maxDepth,
2571 FileVisitor<? super Path> visitor)
2572 throws IOException
2573 {
2574 if (maxDepth < 0)
2575 throw new IllegalArgumentException("'maxDepth' is negative");
2576 new FileTreeWalker(options, visitor, maxDepth).walk(start);
2577 return start;
2578 }
2579
2580 /**
2581 * Walks a file tree.
2582 *
2583 * <p> This method works as if invoking it were equivalent to evaluating the
2584 * expression:
2585 * <blockquote><pre>
2586 * walkFileTree(start, EnumSet.noneOf(FileVisitOption.class), Integer.MAX_VALUE, visitor)
2587 * </pre></blockquote>
2588 * In other words, it does not follow symbolic links, and visits all levels
2589 * of the file tree.
2590 *
2591 * @param start
2592 * the starting file
2593 * @param visitor
2594 * the file visitor to invoke for each file
2595 *
2596 * @return the starting file
2597 *
2598 * @throws SecurityException
2599 * If the security manager denies access to the starting file.
2600 * In the case of the default provider, the {@link
2601 * SecurityManager#checkRead(String) checkRead} method is invoked
2602 * to check read access to the directory.
2603 * @throws IOException
2604 * if an I/O error is thrown by a visitor method
2605 */
2606 public static Path walkFileTree(Path start, FileVisitor<? super Path> visitor)
2607 throws IOException
2608 {
2609 return walkFileTree(start,
2610 EnumSet.noneOf(FileVisitOption.class),
2611 Integer.MAX_VALUE,
2612 visitor);
2613 }
2614
2615
2616 // -- Utility methods for simple usages --
2617
2618 // buffer size used for reading and writing
2619 private static final int BUFFER_SIZE = 8192;
2620
2621 /**
2622 * Opens a file for reading, returning a {@code BufferedReader} that may be
2623 * used to read text from the file in an efficient manner. Bytes from the
2624 * file are decoded into characters using the specified charset. Reading
2625 * commences at the beginning of the file.
2626 *
2627 * <p> The {@code Reader} methods that read from the file throw {@code
2628 * IOException} if a malformed or unmappable byte sequence is read.
2629 *
2630 * @param path
2631 * the path to the file
2632 * @param cs
2633 * the charset to use for decoding
2634 *
2635 * @return a new buffered reader, with default buffer size, to read text
2636 * from the file
2637 *
2638 * @throws IOException
2639 * if an I/O error occurs opening the file
2640 * @throws SecurityException
2641 * In the case of the default provider, and a security manager is
2642 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2643 * method is invoked to check read access to the file.
2644 *
2645 * @see #readAllLines
2646 */
2647 public static BufferedReader newBufferedReader(Path path, Charset cs)
2648 throws IOException
2649 {
2650 CharsetDecoder decoder = cs.newDecoder();
2651 Reader reader = new InputStreamReader(newInputStream(path), decoder);
2652 return new BufferedReader(reader);
2653 }
2654
2655 /**
2656 * Opens or creates a file for writing, returning a {@code BufferedWriter}
2657 * that may be used to write text to the file in an efficient manner.
2658 * The {@code options} parameter specifies how the the file is created or
2659 * opened. If no options are present then this method works as if the {@link
2660 * StandardOpenOption#CREATE CREATE}, {@link
2661 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
2662 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
2663 * opens the file for writing, creating the file if it doesn't exist, or
2664 * initially truncating an existing {@link #isRegularFile regular-file} to
2665 * a size of {@code 0} if it exists.
2666 *
2667 * <p> The {@code Writer} methods to write text throw {@code IOException}
2668 * if the text cannot be encoded using the specified charset.
2669 *
2670 * @param path
2671 * the path to the file
2672 * @param cs
2673 * the charset to use for encoding
2674 * @param options
2675 * options specifying how the file is opened
2676 *
2677 * @return a new buffered writer, with default buffer size, to write text
2678 * to the file
2679 *
2680 * @throws IOException
2681 * if an I/O error occurs opening or creating the file
2682 * @throws UnsupportedOperationException
2683 * if an unsupported option is specified
2684 * @throws SecurityException
2685 * In the case of the default provider, and a security manager is
2686 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2687 * method is invoked to check write access to the file.
2688 *
2689 * @see #write(Path,Iterable,Charset,OpenOption[])
2690 */
2691 public static BufferedWriter newBufferedWriter(Path path, Charset cs,
2692 OpenOption... options)
2693 throws IOException
2694 {
2695 CharsetEncoder encoder = cs.newEncoder();
2696 Writer writer = new OutputStreamWriter(newOutputStream(path, options), encoder);
2697 return new BufferedWriter(writer);
2698 }
2699
2700 /**
2701 * Reads all bytes from an input stream and writes them to an output stream.
2702 */
2703 private static long copy(InputStream source, OutputStream sink)
2704 throws IOException
2705 {
2706 long nread = 0L;
2707 byte[] buf = new byte[BUFFER_SIZE];
2708 int n;
2709 while ((n = source.read(buf)) > 0) {
2710 sink.write(buf, 0, n);
2711 nread += n;
2712 }
2713 return nread;
2714 }
2715
2716 /**
2717 * Copies all bytes from an input stream to a file. On return, the input
2718 * stream will be at end of stream.
2719 *
2720 * <p> By default, the copy fails if the target file already exists or is a
2721 * symbolic link. If the {@link StandardCopyOption#REPLACE_EXISTING
2722 * REPLACE_EXISTING} option is specified, and the target file already exists,
2723 * then it is replaced if it is not a non-empty directory. If the target
2724 * file exists and is a symbolic link, then the symbolic link is replaced.
2725 * In this release, the {@code REPLACE_EXISTING} option is the only option
2726 * required to be supported by this method. Additional options may be
2727 * supported in future releases.
2728 *
2729 * <p> If an I/O error occurs reading from the input stream or writing to
2730 * the file, then it may do so after the target file has been created and
2731 * after some bytes have been read or written. Consequently the input
2732 * stream may not be at end of stream and may be in an inconsistent state.
2733 * It is strongly recommended that the input stream be promptly closed if an
2734 * I/O error occurs.
2735 *
2736 * <p> This method may block indefinitely reading from the input stream (or
2737 * writing to the file). The behavior for the case that the input stream is
2738 * <i>asynchronously closed</i> or the thread interrupted during the copy is
2739 * highly input stream and file system provider specific and therefore not
2740 * specified.
2741 *
2742 * <p> <b>Usage example</b>: Suppose we want to capture a web page and save
2743 * it to a file:
2744 * <pre>
2745 * Path path = ...
2746 * URI u = URI.create("http://java.sun.com/");
2747 * try (InputStream in = u.toURL().openStream()) {
2748 * Files.copy(in, path);
2749 * }
2750 * </pre>
2751 *
2752 * @param in
2753 * the input stream to read from
2754 * @param target
2755 * the path to the file
2756 * @param options
2757 * options specifying how the copy should be done
2758 *
2759 * @return the number of bytes read or written
2760 *
2761 * @throws IOException
2762 * if an I/O error occurs when reading or writing
2763 * @throws FileAlreadyExistsException
2764 * if the target file exists but cannot be replaced because the
2765 * {@code REPLACE_EXISTING} option is not specified <i>(optional
2766 * specific exception)</i>
2767 * @throws DirectoryNotEmptyException
2768 * the {@code REPLACE_EXISTING} option is specified but the file
2769 * cannot be replaced because it is a non-empty directory
2770 * <i>(optional specific exception)</i> *
2771 * @throws UnsupportedOperationException
2772 * if {@code options} contains a copy option that is not supported
2773 * @throws SecurityException
2774 * In the case of the default provider, and a security manager is
2775 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2776 * method is invoked to check write access to the file. Where the
2777 * {@code REPLACE_EXISTING} option is specified, the security
2778 * manager's {@link SecurityManager#checkDelete(String) checkDelete}
2779 * method is invoked to check that an existing file can be deleted.
2780 */
2781 public static long copy(InputStream in, Path target, CopyOption... options)
2782 throws IOException
2783 {
2784 // ensure not null before opening file
2785 Objects.requireNonNull(in);
2786
2787 // check for REPLACE_EXISTING
2788 boolean replaceExisting = false;
2789 for (CopyOption opt: options) {
2790 if (opt == StandardCopyOption.REPLACE_EXISTING) {
2791 replaceExisting = true;
2792 } else {
2793 if (opt == null) {
2794 throw new NullPointerException("options contains 'null'");
2795 } else {
2796 throw new UnsupportedOperationException(opt + " not supported");
2797 }
2798 }
2799 }
2800
2801 // attempt to delete an existing file
2802 SecurityException se = null;
2803 if (replaceExisting) {
2804 try {
2805 deleteIfExists(target);
2806 } catch (SecurityException x) {
2807 se = x;
2808 }
2809 }
2810
2811 // attempt to create target file. If it fails with
2812 // FileAlreadyExistsException then it may be because the security
2813 // manager prevented us from deleting the file, in which case we just
2814 // throw the SecurityException.
2815 OutputStream ostream;
2816 try {
2817 ostream = newOutputStream(target, StandardOpenOption.CREATE_NEW,
2818 StandardOpenOption.WRITE);
2819 } catch (FileAlreadyExistsException x) {
2820 if (se != null)
2821 throw se;
2822 // someone else won the race and created the file
2823 throw x;
2824 }
2825
2826 // do the copy
2827 try (OutputStream out = ostream) {
2828 return copy(in, out);
2829 }
2830 }
2831
2832 /**
2833 * Copies all bytes from a file to an output stream.
2834 *
2835 * <p> If an I/O error occurs reading from the file or writing to the output
2836 * stream, then it may do so after some bytes have been read or written.
2837 * Consequently the output stream may be in an inconsistent state. It is
2838 * strongly recommended that the output stream be promptly closed if an I/O
2839 * error occurs.
2840 *
2841 * <p> This method may block indefinitely writing to the output stream (or
2842 * reading from the file). The behavior for the case that the output stream
2843 * is <i>asynchronously closed</i> or the thread interrupted during the copy
2844 * is highly output stream and file system provider specific and therefore
2845 * not specified.
2846 *
2847 * <p> Note that if the given output stream is {@link java.io.Flushable}
2848 * then its {@link java.io.Flushable#flush flush} method may need to invoked
2849 * after this method completes so as to flush any buffered output.
2850 *
2851 * @param source
2852 * the path to the file
2853 * @param out
2854 * the output stream to write to
2855 *
2856 * @return the number of bytes read or written
2857 *
2858 * @throws IOException
2859 * if an I/O error occurs when reading or writing
2860 * @throws SecurityException
2861 * In the case of the default provider, and a security manager is
2862 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2863 * method is invoked to check read access to the file.
2864 */
2865 public static long copy(Path source, OutputStream out) throws IOException {
2866 // ensure not null before opening file
2867 Objects.requireNonNull(out);
2868
2869 try (InputStream in = newInputStream(source)) {
2870 return copy(in, out);
2871 }
2872 }
2873
2874 /**
2875 * Read all the bytes from an input stream. The {@code initialSize}
2876 * parameter indicates the initial size of the byte[] to allocate.
2877 */
2878 private static byte[] read(InputStream source, int initialSize)
2879 throws IOException
2880 {
2881 int capacity = initialSize;
2882 byte[] buf = new byte[capacity];
2883 int nread = 0;
2884 int rem = buf.length;
2885 int n;
2886 // read to EOF which may read more or less than initialSize (eg: file
2887 // is truncated while we are reading)
2888 while ((n = source.read(buf, nread, rem)) > 0) {
2889 nread += n;
2890 rem -= n;
2891 assert rem >= 0;
2892 if (rem == 0) {
2893 // need larger buffer
2894 int newCapacity = capacity << 1;
2895 if (newCapacity < 0) {
2896 if (capacity == Integer.MAX_VALUE)
2897 throw new OutOfMemoryError("Required array size too large");
2898 newCapacity = Integer.MAX_VALUE;
2899 }
2900 rem = newCapacity - capacity;
2901 buf = Arrays.copyOf(buf, newCapacity);
2902 capacity = newCapacity;
2903 }
2904 }
2905 return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
2906 }
2907
2908 /**
2909 * Read all the bytes from a file. The method ensures that the file is
2910 * closed when all bytes have been read or an I/O error, or other runtime
2911 * exception, is thrown.
2912 *
2913 * <p> Note that this method is intended for simple cases where it is
2914 * convenient to read all bytes into a byte array. It is not intended for
2915 * reading in large files.
2916 *
2917 * @param path
2918 * the path to the file
2919 *
2920 * @return a byte array containing the bytes read from the file
2921 *
2922 * @throws IOException
2923 * if an I/O error occurs reading from the stream
2924 * @throws OutOfMemoryError
2925 * if an array of the required size cannot be allocated, for
2926 * example the file is larger that {@code 2GB}
2927 * @throws SecurityException
2928 * In the case of the default provider, and a security manager is
2929 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2930 * method is invoked to check read access to the file.
2931 */
2932 public static byte[] readAllBytes(Path path) throws IOException {
2933 long size = size(path);
2934 if (size > (long)Integer.MAX_VALUE)
2935 throw new OutOfMemoryError("Required array size too large");
2936
2937 try (InputStream in = newInputStream(path)) {
2938 return read(in, (int)size);
2939 }
2940 }
2941
2942 /**
2943 * Read all lines from a file. This method ensures that the file is
2944 * closed when all bytes have been read or an I/O error, or other runtime
2945 * exception, is thrown. Bytes from the file are decoded into characters
2946 * using the specified charset.
2947 *
2948 * <p> This method recognizes the following as line terminators:
2949 * <ul>
2950 * <li> <code>\u000D</code> followed by <code>\u000A</code>,
2951 * CARRIAGE RETURN followed by LINE FEED </li>
2952 * <li> <code>\u000A</code>, LINE FEED </li>
2953 * <li> <code>\u000D</code>, CARRIAGE RETURN </li>
2954 * </ul>
2955 * <p> Additional Unicode line terminators may be recognized in future
2956 * releases.
2957 *
2958 * <p> Note that this method is intended for simple cases where it is
2959 * convenient to read all lines in a single operation. It is not intended
2960 * for reading in large files.
2961 *
2962 * @param path
2963 * the path to the file
2964 * @param cs
2965 * the charset to use for decoding
2966 *
2967 * @return the lines from the file as a {@code List}; whether the {@code
2968 * List} is modifiable or not is implementation dependent and
2969 * therefore not specified
2970 *
2971 * @throws IOException
2972 * if an I/O error occurs reading from the file or a malformed or
2973 * unmappable byte sequence is read
2974 * @throws SecurityException
2975 * In the case of the default provider, and a security manager is
2976 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2977 * method is invoked to check read access to the file.
2978 *
2979 * @see #newBufferedReader
2980 */
2981 public static List<String> readAllLines(Path path, Charset cs)
2982 throws IOException
2983 {
2984 try (BufferedReader reader = newBufferedReader(path, cs)) {
2985 List<String> result = new ArrayList<>();
2986 for (;;) {
2987 String line = reader.readLine();
2988 if (line == null)
2989 break;
2990 result.add(line);
2991 }
2992 return result;
2993 }
2994 }
2995
2996 /**
2997 * Writes bytes to a file. The {@code options} parameter specifies how the
2998 * the file is created or opened. If no options are present then this method
2999 * works as if the {@link StandardOpenOption#CREATE CREATE}, {@link
3000 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3001 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3002 * opens the file for writing, creating the file if it doesn't exist, or
3003 * initially truncating an existing {@link #isRegularFile regular-file} to
3004 * a size of {@code 0}. All bytes in the byte array are written to the file.
3005 * The method ensures that the file is closed when all bytes have been
3006 * written (or an I/O error or other runtime exception is thrown). If an I/O
3007 * error occurs then it may do so after the file has created or truncated,
3008 * or after some bytes have been written to the file.
3009 *
3010 * <p> <b>Usage example</b>: By default the method creates a new file or
3011 * overwrites an existing file. Suppose you instead want to append bytes
3012 * to an existing file:
3013 * <pre>
3014 * Path path = ...
3015 * byte[] bytes = ...
3016 * Files.write(path, bytes, StandardOpenOption.APPEND);
3017 * </pre>
3018 *
3019 * @param path
3020 * the path to the file
3021 * @param bytes
3022 * the byte array with the bytes to write
3023 * @param options
3024 * options specifying how the file is opened
3025 *
3026 * @return the path
3027 *
3028 * @throws IOException
3029 * if an I/O error occurs writing to or creating the file
3030 * @throws UnsupportedOperationException
3031 * if an unsupported option is specified
3032 * @throws SecurityException
3033 * In the case of the default provider, and a security manager is
3034 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3035 * method is invoked to check write access to the file.
3036 */
3037 public static Path write(Path path, byte[] bytes, OpenOption... options)
3038 throws IOException
3039 {
3040 // ensure bytes is not null before opening file
3041 Objects.requireNonNull(bytes);
3042
3043 try (OutputStream out = Files.newOutputStream(path, options)) {
3044 int len = bytes.length;
3045 int rem = len;
3046 while (rem > 0) {
3047 int n = Math.min(rem, BUFFER_SIZE);
3048 out.write(bytes, (len-rem), n);
3049 rem -= n;
3050 }
3051 }
3052 return path;
3053 }
3054
3055 /**
3056 * Write lines of text to a file. Each line is a char sequence and is
3057 * written to the file in sequence with each line terminated by the
3058 * platform's line separator, as defined by the system property {@code
3059 * line.separator}. Characters are encoded into bytes using the specified
3060 * charset.
3061 *
3062 * <p> The {@code options} parameter specifies how the the file is created
3063 * or opened. If no options are present then this method works as if the
3064 * {@link StandardOpenOption#CREATE CREATE}, {@link
3065 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3066 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3067 * opens the file for writing, creating the file if it doesn't exist, or
3068 * initially truncating an existing {@link #isRegularFile regular-file} to
3069 * a size of {@code 0}. The method ensures that the file is closed when all
3070 * lines have been written (or an I/O error or other runtime exception is
3071 * thrown). If an I/O error occurs then it may do so after the file has
3072 * created or truncated, or after some bytes have been written to the file.
3073 *
3074 * @param path
3075 * the path to the file
3076 * @param lines
3077 * an object to iterate over the char sequences
3078 * @param cs
3079 * the charset to use for encoding
3080 * @param options
3081 * options specifying how the file is opened
3082 *
3083 * @return the path
3084 *
3085 * @throws IOException
3086 * if an I/O error occurs writing to or creating the file, or the
3087 * text cannot be encoded using the specified charset
3088 * @throws UnsupportedOperationException
3089 * if an unsupported option is specified
3090 * @throws SecurityException
3091 * In the case of the default provider, and a security manager is
3092 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3093 * method is invoked to check write access to the file.
3094 */
3095 public static Path write(Path path, Iterable<? extends CharSequence> lines,
3096 Charset cs, OpenOption... options)
3097 throws IOException
3098 {
3099 // ensure lines is not null before opening file
3100 Objects.requireNonNull(lines);
3101 CharsetEncoder encoder = cs.newEncoder();
3102 OutputStream out = newOutputStream(path, options);
3103 try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, encoder))) {
3104 for (CharSequence line: lines) {
3105 writer.append(line);
3106 writer.newLine();
3107 }
3108 }
3109 return path;
3110 }
3111 }