1 /*
2 * Copyright (c) 2007, 2019, 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.io.BufferedReader;
29 import java.io.BufferedWriter;
30 import java.io.Closeable;
31 import java.io.File;
32 import java.io.IOException;
33 import java.io.InputStream;
34 import java.io.InputStreamReader;
35 import java.io.OutputStream;
36 import java.io.OutputStreamWriter;
37 import java.io.Reader;
38 import java.io.UncheckedIOException;
39 import java.io.Writer;
40 import java.nio.channels.Channels;
41 import java.nio.channels.FileChannel;
42 import java.nio.channels.SeekableByteChannel;
43 import java.nio.charset.Charset;
44 import java.nio.charset.CharsetDecoder;
45 import java.nio.charset.CharsetEncoder;
46 import java.nio.charset.StandardCharsets;
47 import java.nio.file.attribute.BasicFileAttributeView;
48 import java.nio.file.attribute.BasicFileAttributes;
49 import java.nio.file.attribute.DosFileAttributes; // javadoc
50 import java.nio.file.attribute.FileAttribute;
51 import java.nio.file.attribute.FileAttributeView;
52 import java.nio.file.attribute.FileOwnerAttributeView;
53 import java.nio.file.attribute.FileStoreAttributeView;
54 import java.nio.file.attribute.FileTime;
55 import java.nio.file.attribute.PosixFileAttributeView;
56 import java.nio.file.attribute.PosixFileAttributes;
57 import java.nio.file.attribute.PosixFilePermission;
58 import java.nio.file.attribute.UserPrincipal;
59 import java.nio.file.spi.FileSystemProvider;
60 import java.nio.file.spi.FileTypeDetector;
61 import java.security.AccessController;
62 import java.security.PrivilegedAction;
63 import java.util.ArrayList;
64 import java.util.Arrays;
65 import java.util.Collections;
66 import java.util.EnumSet;
67 import java.util.HashSet;
68 import java.util.Iterator;
69 import java.util.List;
70 import java.util.Map;
71 import java.util.Objects;
72 import java.util.ServiceLoader;
73 import java.util.Set;
74 import java.util.Spliterator;
75 import java.util.Spliterators;
76 import java.util.function.BiPredicate;
77 import java.util.stream.Stream;
78 import java.util.stream.StreamSupport;
79
80 import sun.nio.ch.FileChannelImpl;
81 import sun.nio.fs.AbstractFileSystemProvider;
82
83 /**
84 * This class consists exclusively of static methods that operate on files,
85 * directories, or other types of files.
86 *
87 * <p> In most cases, the methods defined here will delegate to the associated
88 * file system provider to perform the file operations.
89 *
90 * @since 1.7
91 */
92
93 public final class Files {
94 // buffer size used for reading and writing
95 private static final int BUFFER_SIZE = 8192;
96
97 private Files() { }
98
99 /**
100 * Returns the {@code FileSystemProvider} to delegate to.
101 */
102 private static FileSystemProvider provider(Path path) {
103 return path.getFileSystem().provider();
104 }
105
106 /**
107 * Convert a Closeable to a Runnable by converting checked IOException
108 * to UncheckedIOException
109 */
110 private static Runnable asUncheckedRunnable(Closeable c) {
111 return () -> {
112 try {
113 c.close();
114 } catch (IOException e) {
115 throw new UncheckedIOException(e);
116 }
117 };
118 }
119
120 // -- File contents --
121
122 /**
123 * Opens a file, returning an input stream to read from the file. The stream
124 * will not be buffered, and is not required to support the {@link
125 * InputStream#mark mark} or {@link InputStream#reset reset} methods. The
126 * stream will be safe for access by multiple concurrent threads. Reading
127 * commences at the beginning of the file. Whether the returned stream is
128 * <i>asynchronously closeable</i> and/or <i>interruptible</i> is highly
129 * file system provider specific and therefore not specified.
130 *
131 * <p> The {@code options} parameter determines how the file is opened.
132 * If no options are present then it is equivalent to opening the file with
133 * the {@link StandardOpenOption#READ READ} option. In addition to the {@code
134 * READ} option, an implementation may also support additional implementation
135 * specific options.
136 *
137 * @param path
138 * the path to the file to open
139 * @param options
140 * options specifying how the file is opened
141 *
142 * @return a new input stream
143 *
144 * @throws IllegalArgumentException
145 * if an invalid combination of options is specified
146 * @throws UnsupportedOperationException
147 * if an unsupported option is specified
148 * @throws IOException
149 * if an I/O error occurs
150 * @throws SecurityException
151 * In the case of the default provider, and a security manager is
152 * installed, the {@link SecurityManager#checkRead(String) checkRead}
153 * method is invoked to check read access to the file.
154 */
155 public static InputStream newInputStream(Path path, OpenOption... options)
156 throws IOException
157 {
158 return provider(path).newInputStream(path, options);
159 }
160
161 /**
162 * Opens or creates a file, returning an output stream that may be used to
163 * write bytes to the file. The resulting stream will not be buffered. The
164 * stream will be safe for access by multiple concurrent threads. Whether
165 * the returned stream is <i>asynchronously closeable</i> and/or
166 * <i>interruptible</i> is highly file system provider specific and
167 * therefore not specified.
168 *
169 * <p> This method opens or creates a file in exactly the manner specified
170 * by the {@link #newByteChannel(Path,Set,FileAttribute[]) newByteChannel}
171 * method with the exception that the {@link StandardOpenOption#READ READ}
172 * option may not be present in the array of options. If no options are
173 * present then this method works as if the {@link StandardOpenOption#CREATE
174 * CREATE}, {@link StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING},
175 * and {@link StandardOpenOption#WRITE WRITE} options are present. In other
176 * words, it opens the file for writing, creating the file if it doesn't
177 * exist, or initially truncating an existing {@link #isRegularFile
178 * regular-file} to a size of {@code 0} if it exists.
179 *
180 * <p> <b>Usage Examples:</b>
181 * <pre>
182 * Path path = ...
183 *
184 * // truncate and overwrite an existing file, or create the file if
185 * // it doesn't initially exist
186 * OutputStream out = Files.newOutputStream(path);
187 *
188 * // append to an existing file, fail if the file does not exist
189 * out = Files.newOutputStream(path, APPEND);
190 *
191 * // append to an existing file, create file if it doesn't initially exist
192 * out = Files.newOutputStream(path, CREATE, APPEND);
193 *
194 * // always create new file, failing if it already exists
195 * out = Files.newOutputStream(path, CREATE_NEW);
196 * </pre>
197 *
198 * @param path
199 * the path to the file to open or create
200 * @param options
201 * options specifying how the file is opened
202 *
203 * @return a new output stream
204 *
205 * @throws IllegalArgumentException
206 * if {@code options} contains an invalid combination of options
207 * @throws UnsupportedOperationException
208 * if an unsupported option is specified
209 * @throws IOException
210 * if an I/O error occurs
211 * @throws SecurityException
212 * In the case of the default provider, and a security manager is
213 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
214 * method is invoked to check write access to the file. The {@link
215 * SecurityManager#checkDelete(String) checkDelete} method is
216 * invoked to check delete access if the file is opened with the
217 * {@code DELETE_ON_CLOSE} option.
218 */
219 public static OutputStream newOutputStream(Path path, OpenOption... options)
220 throws IOException
221 {
222 return provider(path).newOutputStream(path, options);
223 }
224
225 /**
226 * Opens or creates a file, returning a seekable byte channel to access the
227 * file.
228 *
229 * <p> The {@code options} parameter determines how the file is opened.
230 * The {@link StandardOpenOption#READ READ} and {@link
231 * StandardOpenOption#WRITE WRITE} options determine if the file should be
232 * opened for reading and/or writing. If neither option (or the {@link
233 * StandardOpenOption#APPEND APPEND} option) is present then the file is
234 * opened for reading. By default reading or writing commence at the
235 * beginning of the file.
236 *
237 * <p> In the addition to {@code READ} and {@code WRITE}, the following
238 * options may be present:
239 *
240 * <table class="striped">
241 * <caption style="display:none">Options</caption>
242 * <thead>
243 * <tr> <th scope="col">Option</th> <th scope="col">Description</th> </tr>
244 * </thead>
245 * <tbody>
246 * <tr>
247 * <th scope="row"> {@link StandardOpenOption#APPEND APPEND} </th>
248 * <td> If this option is present then the file is opened for writing and
249 * each invocation of the channel's {@code write} method first advances
250 * the position to the end of the file and then writes the requested
251 * data. Whether the advancement of the position and the writing of the
252 * data are done in a single atomic operation is system-dependent and
253 * therefore unspecified. This option may not be used in conjunction
254 * with the {@code READ} or {@code TRUNCATE_EXISTING} options. </td>
255 * </tr>
256 * <tr>
257 * <th scope="row"> {@link StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING} </th>
258 * <td> If this option is present then the existing file is truncated to
259 * a size of 0 bytes. This option is ignored when the file is opened only
260 * for reading. </td>
261 * </tr>
262 * <tr>
263 * <th scope="row"> {@link StandardOpenOption#CREATE_NEW CREATE_NEW} </th>
264 * <td> If this option is present then a new file is created, failing if
265 * the file already exists or is a symbolic link. When creating a file the
266 * check for the existence of the file and the creation of the file if it
267 * does not exist is atomic with respect to other file system operations.
268 * This option is ignored when the file is opened only for reading. </td>
269 * </tr>
270 * <tr>
271 * <th scope="row" > {@link StandardOpenOption#CREATE CREATE} </th>
272 * <td> If this option is present then an existing file is opened if it
273 * exists, otherwise a new file is created. This option is ignored if the
274 * {@code CREATE_NEW} option is also present or the file is opened only
275 * for reading. </td>
276 * </tr>
277 * <tr>
278 * <th scope="row" > {@link StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE} </th>
279 * <td> When this option is present then the implementation makes a
280 * <em>best effort</em> attempt to delete the file when closed by the
281 * {@link SeekableByteChannel#close close} method. If the {@code close}
282 * method is not invoked then a <em>best effort</em> attempt is made to
283 * delete the file when the Java virtual machine terminates. </td>
284 * </tr>
285 * <tr>
286 * <th scope="row">{@link StandardOpenOption#SPARSE SPARSE} </th>
287 * <td> When creating a new file this option is a <em>hint</em> that the
288 * new file will be sparse. This option is ignored when not creating
289 * a new file. </td>
290 * </tr>
291 * <tr>
292 * <th scope="row"> {@link StandardOpenOption#SYNC SYNC} </th>
293 * <td> Requires that every update to the file's content or metadata be
294 * written synchronously to the underlying storage device. (see <a
295 * href="package-summary.html#integrity"> Synchronized I/O file
296 * integrity</a>). </td>
297 * </tr>
298 * <tr>
299 * <th scope="row"> {@link StandardOpenOption#DSYNC DSYNC} </th>
300 * <td> Requires that every update to the file's content be written
301 * synchronously to the underlying storage device. (see <a
302 * href="package-summary.html#integrity"> Synchronized I/O file
303 * integrity</a>). </td>
304 * </tr>
305 * </tbody>
306 * </table>
307 *
308 * <p> An implementation may also support additional implementation specific
309 * options.
310 *
311 * <p> The {@code attrs} parameter is optional {@link FileAttribute
312 * file-attributes} to set atomically when a new file is created.
313 *
314 * <p> In the case of the default provider, the returned seekable byte channel
315 * is a {@link java.nio.channels.FileChannel}.
316 *
317 * <p> <b>Usage Examples:</b>
318 * <pre>{@code
319 * Path path = ...
320 *
321 * // open file for reading
322 * ReadableByteChannel rbc = Files.newByteChannel(path, EnumSet.of(READ)));
323 *
324 * // open file for writing to the end of an existing file, creating
325 * // the file if it doesn't already exist
326 * WritableByteChannel wbc = Files.newByteChannel(path, EnumSet.of(CREATE,APPEND));
327 *
328 * // create file with initial permissions, opening it for both reading and writing
329 * FileAttribute<Set<PosixFilePermission>> perms = ...
330 * SeekableByteChannel sbc =
331 * Files.newByteChannel(path, EnumSet.of(CREATE_NEW,READ,WRITE), perms);
332 * }</pre>
333 *
334 * @param path
335 * the path to the file to open or create
336 * @param options
337 * options specifying how the file is opened
338 * @param attrs
339 * an optional list of file attributes to set atomically when
340 * creating the file
341 *
342 * @return a new seekable byte channel
343 *
344 * @throws IllegalArgumentException
345 * if the set contains an invalid combination of options
346 * @throws UnsupportedOperationException
347 * if an unsupported open option is specified or the array contains
348 * attributes that cannot be set atomically when creating the file
349 * @throws FileAlreadyExistsException
350 * if a file of that name already exists and the {@link
351 * StandardOpenOption#CREATE_NEW CREATE_NEW} option is specified
352 * <i>(optional specific exception)</i>
353 * @throws IOException
354 * if an I/O error occurs
355 * @throws SecurityException
356 * In the case of the default provider, and a security manager is
357 * installed, the {@link SecurityManager#checkRead(String) checkRead}
358 * method is invoked to check read access to the path if the file is
359 * opened for reading. The {@link SecurityManager#checkWrite(String)
360 * checkWrite} method is invoked to check write access to the path
361 * if the file is opened for writing. The {@link
362 * SecurityManager#checkDelete(String) checkDelete} method is
363 * invoked to check delete access if the file is opened with the
364 * {@code DELETE_ON_CLOSE} option.
365 *
366 * @see java.nio.channels.FileChannel#open(Path,Set,FileAttribute[])
367 */
368 public static SeekableByteChannel newByteChannel(Path path,
369 Set<? extends OpenOption> options,
370 FileAttribute<?>... attrs)
371 throws IOException
372 {
373 return provider(path).newByteChannel(path, options, attrs);
374 }
375
376 /**
377 * Opens or creates a file, returning a seekable byte channel to access the
378 * file.
379 *
380 * <p> This method opens or creates a file in exactly the manner specified
381 * by the {@link #newByteChannel(Path,Set,FileAttribute[]) newByteChannel}
382 * method.
383 *
384 * @param path
385 * the path to the file to open or create
386 * @param options
387 * options specifying how the file is opened
388 *
389 * @return a new seekable byte channel
390 *
391 * @throws IllegalArgumentException
392 * if the set contains an invalid combination of options
393 * @throws UnsupportedOperationException
394 * if an unsupported open option is specified
395 * @throws FileAlreadyExistsException
396 * if a file of that name already exists and the {@link
397 * StandardOpenOption#CREATE_NEW CREATE_NEW} option is specified
398 * <i>(optional specific exception)</i>
399 * @throws IOException
400 * if an I/O error occurs
401 * @throws SecurityException
402 * In the case of the default provider, and a security manager is
403 * installed, the {@link SecurityManager#checkRead(String) checkRead}
404 * method is invoked to check read access to the path if the file is
405 * opened for reading. The {@link SecurityManager#checkWrite(String)
406 * checkWrite} method is invoked to check write access to the path
407 * if the file is opened for writing. The {@link
408 * SecurityManager#checkDelete(String) checkDelete} method is
409 * invoked to check delete access if the file is opened with the
410 * {@code DELETE_ON_CLOSE} option.
411 *
412 * @see java.nio.channels.FileChannel#open(Path,OpenOption[])
413 */
414 public static SeekableByteChannel newByteChannel(Path path, OpenOption... options)
415 throws IOException
416 {
417 Set<OpenOption> set;
418 if (options.length == 0) {
419 set = Collections.emptySet();
420 } else {
421 set = new HashSet<>();
422 Collections.addAll(set, options);
423 }
424 return newByteChannel(path, set);
425 }
426
427 // -- Directories --
428
429 private static class AcceptAllFilter
430 implements DirectoryStream.Filter<Path>
431 {
432 private AcceptAllFilter() { }
433
434 @Override
435 public boolean accept(Path entry) { return true; }
436
437 static final AcceptAllFilter FILTER = new AcceptAllFilter();
438 }
439
440 /**
441 * Opens a directory, returning a {@link DirectoryStream} to iterate over
442 * all entries in the directory. The elements returned by the directory
443 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
444 * Path}, each one representing an entry in the directory. The {@code Path}
445 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
446 * name of the directory entry against {@code dir}.
447 *
448 * <p> When not using the try-with-resources construct, then directory
449 * stream's {@code close} method should be invoked after iteration is
450 * completed so as to free any resources held for the open directory.
451 *
452 * <p> When an implementation supports operations on entries in the
453 * directory that execute in a race-free manner then the returned directory
454 * stream is a {@link SecureDirectoryStream}.
455 *
456 * @param dir
457 * the path to the directory
458 *
459 * @return a new and open {@code DirectoryStream} object
460 *
461 * @throws NotDirectoryException
462 * if the file could not otherwise be opened because it is not
463 * a directory <i>(optional specific exception)</i>
464 * @throws IOException
465 * if an I/O error occurs
466 * @throws SecurityException
467 * In the case of the default provider, and a security manager is
468 * installed, the {@link SecurityManager#checkRead(String) checkRead}
469 * method is invoked to check read access to the directory.
470 */
471 public static DirectoryStream<Path> newDirectoryStream(Path dir)
472 throws IOException
473 {
474 return provider(dir).newDirectoryStream(dir, AcceptAllFilter.FILTER);
475 }
476
477 /**
478 * Opens a directory, returning a {@link DirectoryStream} to iterate over
479 * the entries in the directory. The elements returned by the directory
480 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
481 * Path}, each one representing an entry in the directory. The {@code Path}
482 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
483 * name of the directory entry against {@code dir}. The entries returned by
484 * the iterator are filtered by matching the {@code String} representation
485 * of their file names against the given <em>globbing</em> pattern.
486 *
487 * <p> For example, suppose we want to iterate over the files ending with
488 * ".java" in a directory:
489 * <pre>
490 * Path dir = ...
491 * try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, "*.java")) {
492 * :
493 * }
494 * </pre>
495 *
496 * <p> The globbing pattern is specified by the {@link
497 * FileSystem#getPathMatcher getPathMatcher} method.
498 *
499 * <p> When not using the try-with-resources construct, then directory
500 * stream's {@code close} method should be invoked after iteration is
501 * completed so as to free any resources held for the open directory.
502 *
503 * <p> When an implementation supports operations on entries in the
504 * directory that execute in a race-free manner then the returned directory
505 * stream is a {@link SecureDirectoryStream}.
506 *
507 * @param dir
508 * the path to the directory
509 * @param glob
510 * the glob pattern
511 *
512 * @return a new and open {@code DirectoryStream} object
513 *
514 * @throws java.util.regex.PatternSyntaxException
515 * if the pattern is invalid
516 * @throws NotDirectoryException
517 * if the file could not otherwise be opened because it is not
518 * a directory <i>(optional specific exception)</i>
519 * @throws IOException
520 * if an I/O error occurs
521 * @throws SecurityException
522 * In the case of the default provider, and a security manager is
523 * installed, the {@link SecurityManager#checkRead(String) checkRead}
524 * method is invoked to check read access to the directory.
525 */
526 public static DirectoryStream<Path> newDirectoryStream(Path dir, String glob)
527 throws IOException
528 {
529 // avoid creating a matcher if all entries are required.
530 if (glob.equals("*"))
531 return newDirectoryStream(dir);
532
533 // create a matcher and return a filter that uses it.
534 FileSystem fs = dir.getFileSystem();
535 final PathMatcher matcher = fs.getPathMatcher("glob:" + glob);
536 DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<>() {
537 @Override
538 public boolean accept(Path entry) {
539 return matcher.matches(entry.getFileName());
540 }
541 };
542 return fs.provider().newDirectoryStream(dir, filter);
543 }
544
545 /**
546 * Opens a directory, returning a {@link DirectoryStream} to iterate over
547 * the entries in the directory. The elements returned by the directory
548 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
549 * Path}, each one representing an entry in the directory. The {@code Path}
550 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
551 * name of the directory entry against {@code dir}. The entries returned by
552 * the iterator are filtered by the given {@link DirectoryStream.Filter
553 * filter}.
554 *
555 * <p> When not using the try-with-resources construct, then directory
556 * stream's {@code close} method should be invoked after iteration is
557 * completed so as to free any resources held for the open directory.
558 *
559 * <p> Where the filter terminates due to an uncaught error or runtime
560 * exception then it is propagated to the {@link Iterator#hasNext()
561 * hasNext} or {@link Iterator#next() next} method. Where an {@code
562 * IOException} is thrown, it results in the {@code hasNext} or {@code
563 * next} method throwing a {@link DirectoryIteratorException} with the
564 * {@code IOException} as the cause.
565 *
566 * <p> When an implementation supports operations on entries in the
567 * directory that execute in a race-free manner then the returned directory
568 * stream is a {@link SecureDirectoryStream}.
569 *
570 * <p> <b>Usage Example:</b>
571 * Suppose we want to iterate over the files in a directory that are
572 * larger than 8K.
573 * <pre>
574 * DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
575 * public boolean accept(Path file) throws IOException {
576 * return (Files.size(file) > 8192L);
577 * }
578 * };
579 * Path dir = ...
580 * try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, filter)) {
581 * :
582 * }
583 * </pre>
584 *
585 * @param dir
586 * the path to the directory
587 * @param filter
588 * the directory stream filter
589 *
590 * @return a new and open {@code DirectoryStream} object
591 *
592 * @throws NotDirectoryException
593 * if the file could not otherwise be opened because it is not
594 * a directory <i>(optional specific exception)</i>
595 * @throws IOException
596 * if an I/O error occurs
597 * @throws SecurityException
598 * In the case of the default provider, and a security manager is
599 * installed, the {@link SecurityManager#checkRead(String) checkRead}
600 * method is invoked to check read access to the directory.
601 */
602 public static DirectoryStream<Path> newDirectoryStream(Path dir,
603 DirectoryStream.Filter<? super Path> filter)
604 throws IOException
605 {
606 return provider(dir).newDirectoryStream(dir, filter);
607 }
608
609 // -- Creation and deletion --
610
611 private static final Set<OpenOption> DEFAULT_CREATE_OPTIONS =
612 Set.of(StandardOpenOption.CREATE_NEW, StandardOpenOption.WRITE);
613
614 /**
615 * Creates a new and empty file, failing if the file already exists. The
616 * check for the existence of the file and the creation of the new file if
617 * it does not exist are a single operation that is atomic with respect to
618 * all other filesystem activities that might affect the directory.
619 *
620 * <p> The {@code attrs} parameter is optional {@link FileAttribute
621 * file-attributes} to set atomically when creating the file. Each attribute
622 * is identified by its {@link FileAttribute#name name}. If more than one
623 * attribute of the same name is included in the array then all but the last
624 * occurrence is ignored.
625 *
626 * @param path
627 * the path to the file to create
628 * @param attrs
629 * an optional list of file attributes to set atomically when
630 * creating the file
631 *
632 * @return the file
633 *
634 * @throws UnsupportedOperationException
635 * if the array contains an attribute that cannot be set atomically
636 * when creating the file
637 * @throws FileAlreadyExistsException
638 * if a file of that name already exists
639 * <i>(optional specific exception)</i>
640 * @throws IOException
641 * if an I/O error occurs or the parent directory does not exist
642 * @throws SecurityException
643 * In the case of the default provider, and a security manager is
644 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
645 * method is invoked to check write access to the new file.
646 */
647 public static Path createFile(Path path, FileAttribute<?>... attrs)
648 throws IOException
649 {
650 newByteChannel(path, DEFAULT_CREATE_OPTIONS, attrs).close();
651 return path;
652 }
653
654 /**
655 * Creates a new directory. The check for the existence of the file and the
656 * creation of the directory if it does not exist are a single operation
657 * that is atomic with respect to all other filesystem activities that might
658 * affect the directory. The {@link #createDirectories createDirectories}
659 * method should be used where it is required to create all nonexistent
660 * parent directories first.
661 *
662 * <p> The {@code attrs} parameter is optional {@link FileAttribute
663 * file-attributes} to set atomically when creating the directory. Each
664 * attribute is identified by its {@link FileAttribute#name name}. If more
665 * than one attribute of the same name is included in the array then all but
666 * the last occurrence is ignored.
667 *
668 * @param dir
669 * the directory to create
670 * @param attrs
671 * an optional list of file attributes to set atomically when
672 * creating the directory
673 *
674 * @return the directory
675 *
676 * @throws UnsupportedOperationException
677 * if the array contains an attribute that cannot be set atomically
678 * when creating the directory
679 * @throws FileAlreadyExistsException
680 * if a directory could not otherwise be created because a file of
681 * that name already exists <i>(optional specific exception)</i>
682 * @throws IOException
683 * if an I/O error occurs or the parent directory does not exist
684 * @throws SecurityException
685 * In the case of the default provider, and a security manager is
686 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
687 * method is invoked to check write access to the new directory.
688 */
689 public static Path createDirectory(Path dir, FileAttribute<?>... attrs)
690 throws IOException
691 {
692 provider(dir).createDirectory(dir, attrs);
693 return dir;
694 }
695
696 /**
697 * Creates a directory by creating all nonexistent parent directories first.
698 * Unlike the {@link #createDirectory createDirectory} method, an exception
699 * is not thrown if the directory could not be created because it already
700 * exists.
701 *
702 * <p> The {@code attrs} parameter is optional {@link FileAttribute
703 * file-attributes} to set atomically when creating the nonexistent
704 * directories. Each file attribute is identified by its {@link
705 * FileAttribute#name name}. If more than one attribute of the same name is
706 * included in the array then all but the last occurrence is ignored.
707 *
708 * <p> If this method fails, then it may do so after creating some, but not
709 * all, of the parent directories.
710 *
711 * @param dir
712 * the directory to create
713 *
714 * @param attrs
715 * an optional list of file attributes to set atomically when
716 * creating the directory
717 *
718 * @return the directory
719 *
720 * @throws UnsupportedOperationException
721 * if the array contains an attribute that cannot be set atomically
722 * when creating the directory
723 * @throws FileAlreadyExistsException
724 * if {@code dir} exists but is not a directory <i>(optional specific
725 * exception)</i>
726 * @throws IOException
727 * if an I/O error occurs
728 * @throws SecurityException
729 * in the case of the default provider, and a security manager is
730 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
731 * method is invoked prior to attempting to create a directory and
732 * its {@link SecurityManager#checkRead(String) checkRead} is
733 * invoked for each parent directory that is checked. If {@code
734 * dir} is not an absolute path then its {@link Path#toAbsolutePath
735 * toAbsolutePath} may need to be invoked to get its absolute path.
736 * This may invoke the security manager's {@link
737 * SecurityManager#checkPropertyAccess(String) checkPropertyAccess}
738 * method to check access to the system property {@code user.dir}
739 */
740 public static Path createDirectories(Path dir, FileAttribute<?>... attrs)
741 throws IOException
742 {
743 // attempt to create the directory
744 try {
745 createAndCheckIsDirectory(dir, attrs);
746 return dir;
747 } catch (FileAlreadyExistsException x) {
748 // file exists and is not a directory
749 throw x;
750 } catch (IOException x) {
751 // parent may not exist or other reason
752 }
753 SecurityException se = null;
754 try {
755 dir = dir.toAbsolutePath();
756 } catch (SecurityException x) {
757 // don't have permission to get absolute path
758 se = x;
759 }
760 // find a descendant that exists
761 Path parent = dir.getParent();
762 while (parent != null) {
763 try {
764 provider(parent).checkAccess(parent);
765 break;
766 } catch (NoSuchFileException x) {
767 // does not exist
768 }
769 parent = parent.getParent();
770 }
771 if (parent == null) {
772 // unable to find existing parent
773 if (se == null) {
774 throw new FileSystemException(dir.toString(), null,
775 "Unable to determine if root directory exists");
776 } else {
777 throw se;
778 }
779 }
780
781 // create directories
782 Path child = parent;
783 for (Path name: parent.relativize(dir)) {
784 child = child.resolve(name);
785 createAndCheckIsDirectory(child, attrs);
786 }
787 return dir;
788 }
789
790 /**
791 * Used by createDirectories to attempt to create a directory. A no-op
792 * if the directory already exists.
793 */
794 private static void createAndCheckIsDirectory(Path dir,
795 FileAttribute<?>... attrs)
796 throws IOException
797 {
798 try {
799 createDirectory(dir, attrs);
800 } catch (FileAlreadyExistsException x) {
801 if (!isDirectory(dir, LinkOption.NOFOLLOW_LINKS))
802 throw x;
803 }
804 }
805
806 /**
807 * Creates a new empty file in the specified directory, using the given
808 * prefix and suffix strings to generate its name. The resulting
809 * {@code Path} is associated with the same {@code FileSystem} as the given
810 * directory.
811 *
812 * <p> The details as to how the name of the file is constructed is
813 * implementation dependent and therefore not specified. Where possible
814 * the {@code prefix} and {@code suffix} are used to construct candidate
815 * names in the same manner as the {@link
816 * java.io.File#createTempFile(String,String,File)} method.
817 *
818 * <p> As with the {@code File.createTempFile} methods, this method is only
819 * part of a temporary-file facility. Where used as a <em>work files</em>,
820 * the resulting file may be opened using the {@link
821 * StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE} option so that the
822 * file is deleted when the appropriate {@code close} method is invoked.
823 * Alternatively, a {@link Runtime#addShutdownHook shutdown-hook}, or the
824 * {@link java.io.File#deleteOnExit} mechanism may be used to delete the
825 * file automatically.
826 *
827 * <p> The {@code attrs} parameter is optional {@link FileAttribute
828 * file-attributes} to set atomically when creating the file. Each attribute
829 * is identified by its {@link FileAttribute#name name}. If more than one
830 * attribute of the same name is included in the array then all but the last
831 * occurrence is ignored. When no file attributes are specified, then the
832 * resulting file may have more restrictive access permissions to files
833 * created by the {@link java.io.File#createTempFile(String,String,File)}
834 * method.
835 *
836 * @param dir
837 * the path to directory in which to create the file
838 * @param prefix
839 * the prefix string to be used in generating the file's name;
840 * may be {@code null}
841 * @param suffix
842 * the suffix string to be used in generating the file's name;
843 * may be {@code null}, in which case "{@code .tmp}" is used
844 * @param attrs
845 * an optional list of file attributes to set atomically when
846 * creating the file
847 *
848 * @return the path to the newly created file that did not exist before
849 * this method was invoked
850 *
851 * @throws IllegalArgumentException
852 * if the prefix or suffix parameters cannot be used to generate
853 * a candidate file name
854 * @throws UnsupportedOperationException
855 * if the array contains an attribute that cannot be set atomically
856 * when creating the directory
857 * @throws IOException
858 * if an I/O error occurs or {@code dir} does not exist
859 * @throws SecurityException
860 * In the case of the default provider, and a security manager is
861 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
862 * method is invoked to check write access to the file.
863 */
864 public static Path createTempFile(Path dir,
865 String prefix,
866 String suffix,
867 FileAttribute<?>... attrs)
868 throws IOException
869 {
870 return TempFileHelper.createTempFile(Objects.requireNonNull(dir),
871 prefix, suffix, attrs);
872 }
873
874 /**
875 * Creates an empty file in the default temporary-file directory, using
876 * the given prefix and suffix to generate its name. The resulting {@code
877 * Path} is associated with the default {@code FileSystem}.
878 *
879 * <p> This method works in exactly the manner specified by the
880 * {@link #createTempFile(Path,String,String,FileAttribute[])} method for
881 * the case that the {@code dir} parameter is the temporary-file directory.
882 *
883 * @param prefix
884 * the prefix string to be used in generating the file's name;
885 * may be {@code null}
886 * @param suffix
887 * the suffix string to be used in generating the file's name;
888 * may be {@code null}, in which case "{@code .tmp}" is used
889 * @param attrs
890 * an optional list of file attributes to set atomically when
891 * creating the file
892 *
893 * @return the path to the newly created file that did not exist before
894 * this method was invoked
895 *
896 * @throws IllegalArgumentException
897 * if the prefix or suffix parameters cannot be used to generate
898 * a candidate file name
899 * @throws UnsupportedOperationException
900 * if the array contains an attribute that cannot be set atomically
901 * when creating the directory
902 * @throws IOException
903 * if an I/O error occurs or the temporary-file directory does not
904 * exist
905 * @throws SecurityException
906 * In the case of the default provider, and a security manager is
907 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
908 * method is invoked to check write access to the file.
909 */
910 public static Path createTempFile(String prefix,
911 String suffix,
912 FileAttribute<?>... attrs)
913 throws IOException
914 {
915 return TempFileHelper.createTempFile(null, prefix, suffix, attrs);
916 }
917
918 /**
919 * Creates a new directory in the specified directory, using the given
920 * prefix to generate its name. The resulting {@code Path} is associated
921 * with the same {@code FileSystem} as the given directory.
922 *
923 * <p> The details as to how the name of the directory is constructed is
924 * implementation dependent and therefore not specified. Where possible
925 * the {@code prefix} is used to construct candidate names.
926 *
927 * <p> As with the {@code createTempFile} methods, this method is only
928 * part of a temporary-file facility. A {@link Runtime#addShutdownHook
929 * shutdown-hook}, or the {@link java.io.File#deleteOnExit} mechanism may be
930 * used to delete the directory automatically.
931 *
932 * <p> The {@code attrs} parameter is optional {@link FileAttribute
933 * file-attributes} to set atomically when creating the directory. Each
934 * attribute is identified by its {@link FileAttribute#name name}. If more
935 * than one attribute of the same name is included in the array then all but
936 * the last occurrence is ignored.
937 *
938 * @param dir
939 * the path to directory in which to create the directory
940 * @param prefix
941 * the prefix string to be used in generating the directory's name;
942 * may be {@code null}
943 * @param attrs
944 * an optional list of file attributes to set atomically when
945 * creating the directory
946 *
947 * @return the path to the newly created directory that did not exist before
948 * this method was invoked
949 *
950 * @throws IllegalArgumentException
951 * if the prefix cannot be used to generate a candidate directory name
952 * @throws UnsupportedOperationException
953 * if the array contains an attribute that cannot be set atomically
954 * when creating the directory
955 * @throws IOException
956 * if an I/O error occurs or {@code dir} does not exist
957 * @throws SecurityException
958 * In the case of the default provider, and a security manager is
959 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
960 * method is invoked to check write access when creating the
961 * directory.
962 */
963 public static Path createTempDirectory(Path dir,
964 String prefix,
965 FileAttribute<?>... attrs)
966 throws IOException
967 {
968 return TempFileHelper.createTempDirectory(Objects.requireNonNull(dir),
969 prefix, attrs);
970 }
971
972 /**
973 * Creates a new directory in the default temporary-file directory, using
974 * the given prefix to generate its name. The resulting {@code Path} is
975 * associated with the default {@code FileSystem}.
976 *
977 * <p> This method works in exactly the manner specified by {@link
978 * #createTempDirectory(Path,String,FileAttribute[])} method for the case
979 * that the {@code dir} parameter is the temporary-file directory.
980 *
981 * @param prefix
982 * the prefix string to be used in generating the directory's name;
983 * may be {@code null}
984 * @param attrs
985 * an optional list of file attributes to set atomically when
986 * creating the directory
987 *
988 * @return the path to the newly created directory that did not exist before
989 * this method was invoked
990 *
991 * @throws IllegalArgumentException
992 * if the prefix cannot be used to generate a candidate directory name
993 * @throws UnsupportedOperationException
994 * if the array contains an attribute that cannot be set atomically
995 * when creating the directory
996 * @throws IOException
997 * if an I/O error occurs or the temporary-file directory does not
998 * exist
999 * @throws SecurityException
1000 * In the case of the default provider, and a security manager is
1001 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
1002 * method is invoked to check write access when creating the
1003 * directory.
1004 */
1005 public static Path createTempDirectory(String prefix,
1006 FileAttribute<?>... attrs)
1007 throws IOException
1008 {
1009 return TempFileHelper.createTempDirectory(null, prefix, attrs);
1010 }
1011
1012 /**
1013 * Creates a symbolic link to a target <i>(optional operation)</i>.
1014 *
1015 * <p> The {@code target} parameter is the target of the link. It may be an
1016 * {@link Path#isAbsolute absolute} or relative path and may not exist. When
1017 * the target is a relative path then file system operations on the resulting
1018 * link are relative to the path of the link.
1019 *
1020 * <p> The {@code attrs} parameter is optional {@link FileAttribute
1021 * attributes} to set atomically when creating the link. Each attribute is
1022 * identified by its {@link FileAttribute#name name}. If more than one attribute
1023 * of the same name is included in the array then all but the last occurrence
1024 * is ignored.
1025 *
1026 * <p> Where symbolic links are supported, but the underlying {@link FileStore}
1027 * does not support symbolic links, then this may fail with an {@link
1028 * IOException}. Additionally, some operating systems may require that the
1029 * Java virtual machine be started with implementation specific privileges to
1030 * create symbolic links, in which case this method may throw {@code IOException}.
1031 *
1032 * @param link
1033 * the path of the symbolic link to create
1034 * @param target
1035 * the target of the symbolic link
1036 * @param attrs
1037 * the array of attributes to set atomically when creating the
1038 * symbolic link
1039 *
1040 * @return the path to the symbolic link
1041 *
1042 * @throws UnsupportedOperationException
1043 * if the implementation does not support symbolic links or the
1044 * array contains an attribute that cannot be set atomically when
1045 * creating the symbolic link
1046 * @throws FileAlreadyExistsException
1047 * if a file with the name already exists <i>(optional specific
1048 * exception)</i>
1049 * @throws IOException
1050 * if an I/O error occurs
1051 * @throws SecurityException
1052 * In the case of the default provider, and a security manager
1053 * is installed, it denies {@link LinkPermission}{@code ("symbolic")}
1054 * or its {@link SecurityManager#checkWrite(String) checkWrite}
1055 * method denies write access to the path of the symbolic link.
1056 */
1057 public static Path createSymbolicLink(Path link, Path target,
1058 FileAttribute<?>... attrs)
1059 throws IOException
1060 {
1061 provider(link).createSymbolicLink(link, target, attrs);
1062 return link;
1063 }
1064
1065 /**
1066 * Creates a new link (directory entry) for an existing file <i>(optional
1067 * operation)</i>.
1068 *
1069 * <p> The {@code link} parameter locates the directory entry to create.
1070 * The {@code existing} parameter is the path to an existing file. This
1071 * method creates a new directory entry for the file so that it can be
1072 * accessed using {@code link} as the path. On some file systems this is
1073 * known as creating a "hard link". Whether the file attributes are
1074 * maintained for the file or for each directory entry is file system
1075 * specific and therefore not specified. Typically, a file system requires
1076 * that all links (directory entries) for a file be on the same file system.
1077 * Furthermore, on some platforms, the Java virtual machine may require to
1078 * be started with implementation specific privileges to create hard links
1079 * or to create links to directories.
1080 *
1081 * @param link
1082 * the link (directory entry) to create
1083 * @param existing
1084 * a path to an existing file
1085 *
1086 * @return the path to the link (directory entry)
1087 *
1088 * @throws UnsupportedOperationException
1089 * if the implementation does not support adding an existing file
1090 * to a directory
1091 * @throws FileAlreadyExistsException
1092 * if the entry could not otherwise be created because a file of
1093 * that name already exists <i>(optional specific exception)</i>
1094 * @throws IOException
1095 * if an I/O error occurs
1096 * @throws SecurityException
1097 * In the case of the default provider, and a security manager
1098 * is installed, it denies {@link LinkPermission}{@code ("hard")}
1099 * or its {@link SecurityManager#checkWrite(String) checkWrite}
1100 * method denies write access to either the link or the
1101 * existing file.
1102 */
1103 public static Path createLink(Path link, Path existing) throws IOException {
1104 provider(link).createLink(link, existing);
1105 return link;
1106 }
1107
1108 /**
1109 * Deletes a file.
1110 *
1111 * <p> An implementation may require to examine the file to determine if the
1112 * file is a directory. Consequently this method may not be atomic with respect
1113 * to other file system operations. If the file is a symbolic link then the
1114 * symbolic link itself, not the final target of the link, is deleted.
1115 *
1116 * <p> If the file is a directory then the directory must be empty. In some
1117 * implementations a directory has entries for special files or links that
1118 * are created when the directory is created. In such implementations a
1119 * directory is considered empty when only the special entries exist.
1120 * This method can be used with the {@link #walkFileTree walkFileTree}
1121 * method to delete a directory and all entries in the directory, or an
1122 * entire <i>file-tree</i> where required.
1123 *
1124 * <p> On some operating systems it may not be possible to remove a file when
1125 * it is open and in use by this Java virtual machine or other programs.
1126 *
1127 * @param path
1128 * the path to the file to delete
1129 *
1130 * @throws NoSuchFileException
1131 * if the file does not exist <i>(optional specific exception)</i>
1132 * @throws DirectoryNotEmptyException
1133 * if the file is a directory and could not otherwise be deleted
1134 * because the directory is not empty <i>(optional specific
1135 * exception)</i>
1136 * @throws IOException
1137 * if an I/O error occurs
1138 * @throws SecurityException
1139 * In the case of the default provider, and a security manager is
1140 * installed, the {@link SecurityManager#checkDelete(String)} method
1141 * is invoked to check delete access to the file
1142 */
1143 public static void delete(Path path) throws IOException {
1144 provider(path).delete(path);
1145 }
1146
1147 /**
1148 * Deletes a file if it exists.
1149 *
1150 * <p> As with the {@link #delete(Path) delete(Path)} method, an
1151 * implementation may need to examine the file to determine if the file is a
1152 * directory. Consequently this method may not be atomic with respect to
1153 * other file system operations. If the file is a symbolic link, then the
1154 * symbolic link itself, not the final target of the link, is deleted.
1155 *
1156 * <p> If the file is a directory then the directory must be empty. In some
1157 * implementations a directory has entries for special files or links that
1158 * are created when the directory is created. In such implementations a
1159 * directory is considered empty when only the special entries exist.
1160 *
1161 * <p> On some operating systems it may not be possible to remove a file when
1162 * it is open and in use by this Java virtual machine or other programs.
1163 *
1164 * @param path
1165 * the path to the file to delete
1166 *
1167 * @return {@code true} if the file was deleted by this method; {@code
1168 * false} if the file could not be deleted because it did not
1169 * exist
1170 *
1171 * @throws DirectoryNotEmptyException
1172 * if the file is a directory and could not otherwise be deleted
1173 * because the directory is not empty <i>(optional specific
1174 * exception)</i>
1175 * @throws IOException
1176 * if an I/O error occurs
1177 * @throws SecurityException
1178 * In the case of the default provider, and a security manager is
1179 * installed, the {@link SecurityManager#checkDelete(String)} method
1180 * is invoked to check delete access to the file.
1181 */
1182 public static boolean deleteIfExists(Path path) throws IOException {
1183 return provider(path).deleteIfExists(path);
1184 }
1185
1186 // -- Copying and moving files --
1187
1188 /**
1189 * Copy a file to a target file.
1190 *
1191 * <p> This method copies a file to the target file with the {@code
1192 * options} parameter specifying how the copy is performed. By default, the
1193 * copy fails if the target file already exists or is a symbolic link,
1194 * except if the source and target are the {@link #isSameFile same} file, in
1195 * which case the method completes without copying the file. File attributes
1196 * are not required to be copied to the target file. If symbolic links are
1197 * supported, and the file is a symbolic link, then the final target of the
1198 * link is copied. If the file is a directory then it creates an empty
1199 * directory in the target location (entries in the directory are not
1200 * copied). This method can be used with the {@link #walkFileTree
1201 * walkFileTree} method to copy a directory and all entries in the directory,
1202 * or an entire <i>file-tree</i> where required.
1203 *
1204 * <p> The {@code options} parameter may include any of the following:
1205 *
1206 * <table class="striped">
1207 * <caption style="display:none">Options</caption>
1208 * <thead>
1209 * <tr> <th scope="col">Option</th> <th scope="col">Description</th> </tr>
1210 * </thead>
1211 * <tbody>
1212 * <tr>
1213 * <th scope="row"> {@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING} </th>
1214 * <td> If the target file exists, then the target file is replaced if it
1215 * is not a non-empty directory. If the target file exists and is a
1216 * symbolic link, then the symbolic link itself, not the target of
1217 * the link, is replaced. </td>
1218 * </tr>
1219 * <tr>
1220 * <th scope="row"> {@link StandardCopyOption#COPY_ATTRIBUTES COPY_ATTRIBUTES} </th>
1221 * <td> Attempts to copy the file attributes associated with this file to
1222 * the target file. The exact file attributes that are copied is platform
1223 * and file system dependent and therefore unspecified. Minimally, the
1224 * {@link BasicFileAttributes#lastModifiedTime last-modified-time} is
1225 * copied to the target file if supported by both the source and target
1226 * file stores. Copying of file timestamps may result in precision
1227 * loss. </td>
1228 * </tr>
1229 * <tr>
1230 * <th scope="row"> {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} </th>
1231 * <td> Symbolic links are not followed. If the file is a symbolic link,
1232 * then the symbolic link itself, not the target of the link, is copied.
1233 * It is implementation specific if file attributes can be copied to the
1234 * new link. In other words, the {@code COPY_ATTRIBUTES} option may be
1235 * ignored when copying a symbolic link. </td>
1236 * </tr>
1237 * </tbody>
1238 * </table>
1239 *
1240 * <p> An implementation of this interface may support additional
1241 * implementation specific options.
1242 *
1243 * <p> Copying a file is not an atomic operation. If an {@link IOException}
1244 * is thrown, then it is possible that the target file is incomplete or some
1245 * of its file attributes have not been copied from the source file. When
1246 * the {@code REPLACE_EXISTING} option is specified and the target file
1247 * exists, then the target file is replaced. The check for the existence of
1248 * the file and the creation of the new file may not be atomic with respect
1249 * to other file system activities.
1250 *
1251 * <p> <b>Usage Example:</b>
1252 * Suppose we want to copy a file into a directory, giving it the same file
1253 * name as the source file:
1254 * <pre>
1255 * Path source = ...
1256 * Path newdir = ...
1257 * Files.copy(source, newdir.resolve(source.getFileName());
1258 * </pre>
1259 *
1260 * @param source
1261 * the path to the file to copy
1262 * @param target
1263 * the path to the target file (may be associated with a different
1264 * provider to the source path)
1265 * @param options
1266 * options specifying how the copy should be done
1267 *
1268 * @return the path to the target file
1269 *
1270 * @throws UnsupportedOperationException
1271 * if the array contains a copy option that is not supported
1272 * @throws FileAlreadyExistsException
1273 * if the target file exists but cannot be replaced because the
1274 * {@code REPLACE_EXISTING} option is not specified <i>(optional
1275 * specific exception)</i>
1276 * @throws DirectoryNotEmptyException
1277 * the {@code REPLACE_EXISTING} option is specified but the file
1278 * cannot be replaced because it is a non-empty directory
1279 * <i>(optional specific exception)</i>
1280 * @throws IOException
1281 * if an I/O error occurs
1282 * @throws SecurityException
1283 * In the case of the default provider, and a security manager is
1284 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1285 * method is invoked to check read access to the source file, the
1286 * {@link SecurityManager#checkWrite(String) checkWrite} is invoked
1287 * to check write access to the target file. If a symbolic link is
1288 * copied the security manager is invoked to check {@link
1289 * LinkPermission}{@code ("symbolic")}.
1290 */
1291 public static Path copy(Path source, Path target, CopyOption... options)
1292 throws IOException
1293 {
1294 FileSystemProvider provider = provider(source);
1295 if (provider(target) == provider) {
1296 // same provider
1297 provider.copy(source, target, options);
1298 } else {
1299 // different providers
1300 CopyMoveHelper.copyToForeignTarget(source, target, options);
1301 }
1302 return target;
1303 }
1304
1305 /**
1306 * Move or rename a file to a target file.
1307 *
1308 * <p> By default, this method attempts to move the file to the target
1309 * file, failing if the target file exists except if the source and
1310 * target are the {@link #isSameFile same} file, in which case this method
1311 * has no effect. If the file is a symbolic link then the symbolic link
1312 * itself, not the target of the link, is moved. This method may be
1313 * invoked to move an empty directory. In some implementations a directory
1314 * has entries for special files or links that are created when the
1315 * directory is created. In such implementations a directory is considered
1316 * empty when only the special entries exist. When invoked to move a
1317 * directory that is not empty then the directory is moved if it does not
1318 * require moving the entries in the directory. For example, renaming a
1319 * directory on the same {@link FileStore} will usually not require moving
1320 * the entries in the directory. When moving a directory requires that its
1321 * entries be moved then this method fails (by throwing an {@code
1322 * IOException}). To move a <i>file tree</i> may involve copying rather
1323 * than moving directories and this can be done using the {@link
1324 * #copy copy} method in conjunction with the {@link
1325 * #walkFileTree Files.walkFileTree} utility method.
1326 *
1327 * <p> The {@code options} parameter may include any of the following:
1328 *
1329 * <table class="striped">
1330 * <caption style="display:none">Options</caption>
1331 * <thead>
1332 * <tr> <th scope="col">Option</th> <th scope="col">Description</th> </tr>
1333 * </thead>
1334 * <tbody>
1335 * <tr>
1336 * <th scope="row"> {@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING} </th>
1337 * <td> If the target file exists, then the target file is replaced if it
1338 * is not a non-empty directory. If the target file exists and is a
1339 * symbolic link, then the symbolic link itself, not the target of
1340 * the link, is replaced. </td>
1341 * </tr>
1342 * <tr>
1343 * <th scope="row"> {@link StandardCopyOption#ATOMIC_MOVE ATOMIC_MOVE} </th>
1344 * <td> The move is performed as an atomic file system operation and all
1345 * other options are ignored. If the target file exists then it is
1346 * implementation specific if the existing file is replaced or this method
1347 * fails by throwing an {@link IOException}. If the move cannot be
1348 * performed as an atomic file system operation then {@link
1349 * AtomicMoveNotSupportedException} is thrown. This can arise, for
1350 * example, when the target location is on a different {@code FileStore}
1351 * and would require that the file be copied, or target location is
1352 * associated with a different provider to this object. </td>
1353 * </tbody>
1354 * </table>
1355 *
1356 * <p> An implementation of this interface may support additional
1357 * implementation specific options.
1358 *
1359 * <p> Moving a file will copy the {@link
1360 * BasicFileAttributes#lastModifiedTime last-modified-time} to the target
1361 * file if supported by both source and target file stores. Copying of file
1362 * timestamps may result in precision loss. An implementation may also
1363 * attempt to copy other file attributes but is not required to fail if the
1364 * file attributes cannot be copied. When the move is performed as
1365 * a non-atomic operation, and an {@code IOException} is thrown, then the
1366 * state of the files is not defined. The original file and the target file
1367 * may both exist, the target file may be incomplete or some of its file
1368 * attributes may not been copied from the original file.
1369 *
1370 * <p> <b>Usage Examples:</b>
1371 * Suppose we want to rename a file to "newname", keeping the file in the
1372 * same directory:
1373 * <pre>
1374 * Path source = ...
1375 * Files.move(source, source.resolveSibling("newname"));
1376 * </pre>
1377 * Alternatively, suppose we want to move a file to new directory, keeping
1378 * the same file name, and replacing any existing file of that name in the
1379 * directory:
1380 * <pre>
1381 * Path source = ...
1382 * Path newdir = ...
1383 * Files.move(source, newdir.resolve(source.getFileName()), REPLACE_EXISTING);
1384 * </pre>
1385 *
1386 * @param source
1387 * the path to the file to move
1388 * @param target
1389 * the path to the target file (may be associated with a different
1390 * provider to the source path)
1391 * @param options
1392 * options specifying how the move should be done
1393 *
1394 * @return the path to the target file
1395 *
1396 * @throws UnsupportedOperationException
1397 * if the array contains a copy option that is not supported
1398 * @throws FileAlreadyExistsException
1399 * if the target file exists but cannot be replaced because the
1400 * {@code REPLACE_EXISTING} option is not specified <i>(optional
1401 * specific exception)</i>
1402 * @throws DirectoryNotEmptyException
1403 * the {@code REPLACE_EXISTING} option is specified but the file
1404 * cannot be replaced because it is a non-empty directory, or the
1405 * source is a non-empty directory containing entries that would
1406 * be required to be moved <i>(optional specific exceptions)</i>
1407 * @throws AtomicMoveNotSupportedException
1408 * if the options array contains the {@code ATOMIC_MOVE} option but
1409 * the file cannot be moved as an atomic file system operation.
1410 * @throws IOException
1411 * if an I/O error occurs
1412 * @throws SecurityException
1413 * In the case of the default provider, and a security manager is
1414 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
1415 * method is invoked to check write access to both the source and
1416 * target file.
1417 */
1418 public static Path move(Path source, Path target, CopyOption... options)
1419 throws IOException
1420 {
1421 FileSystemProvider provider = provider(source);
1422 if (provider(target) == provider) {
1423 // same provider
1424 provider.move(source, target, options);
1425 } else {
1426 // different providers
1427 CopyMoveHelper.moveToForeignTarget(source, target, options);
1428 }
1429 return target;
1430 }
1431
1432 // -- Miscellaneous --
1433
1434 /**
1435 * Reads the target of a symbolic link <i>(optional operation)</i>.
1436 *
1437 * <p> If the file system supports <a href="package-summary.html#links">symbolic
1438 * links</a> then this method is used to read the target of the link, failing
1439 * if the file is not a symbolic link. The target of the link need not exist.
1440 * The returned {@code Path} object will be associated with the same file
1441 * system as {@code link}.
1442 *
1443 * @param link
1444 * the path to the symbolic link
1445 *
1446 * @return a {@code Path} object representing the target of the link
1447 *
1448 * @throws UnsupportedOperationException
1449 * if the implementation does not support symbolic links
1450 * @throws NotLinkException
1451 * if the target could otherwise not be read because the file
1452 * is not a symbolic link <i>(optional specific exception)</i>
1453 * @throws IOException
1454 * if an I/O error occurs
1455 * @throws SecurityException
1456 * In the case of the default provider, and a security manager
1457 * is installed, it checks that {@code FilePermission} has been
1458 * granted with the "{@code readlink}" action to read the link.
1459 */
1460 public static Path readSymbolicLink(Path link) throws IOException {
1461 return provider(link).readSymbolicLink(link);
1462 }
1463
1464 /**
1465 * Returns the {@link FileStore} representing the file store where a file
1466 * is located.
1467 *
1468 * <p> Once a reference to the {@code FileStore} is obtained it is
1469 * implementation specific if operations on the returned {@code FileStore},
1470 * or {@link FileStoreAttributeView} objects obtained from it, continue
1471 * to depend on the existence of the file. In particular the behavior is not
1472 * defined for the case that the file is deleted or moved to a different
1473 * file store.
1474 *
1475 * @param path
1476 * the path to the file
1477 *
1478 * @return the file store where the file is stored
1479 *
1480 * @throws IOException
1481 * if an I/O error occurs
1482 * @throws SecurityException
1483 * In the case of the default provider, and a security manager is
1484 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1485 * method is invoked to check read access to the file, and in
1486 * addition it checks
1487 * {@link RuntimePermission}{@code ("getFileStoreAttributes")}
1488 */
1489 public static FileStore getFileStore(Path path) throws IOException {
1490 return provider(path).getFileStore(path);
1491 }
1492
1493 /**
1494 * Tests if two paths locate the same file.
1495 *
1496 * <p> If both {@code Path} objects are {@link Path#equals(Object) equal}
1497 * then this method returns {@code true} without checking if the file exists.
1498 * If the two {@code Path} objects are associated with different providers
1499 * then this method returns {@code false}. Otherwise, this method checks if
1500 * both {@code Path} objects locate the same file, and depending on the
1501 * implementation, may require to open or access both files.
1502 *
1503 * <p> If the file system and files remain static, then this method implements
1504 * an equivalence relation for non-null {@code Paths}.
1505 * <ul>
1506 * <li>It is <i>reflexive</i>: for {@code Path} {@code f},
1507 * {@code isSameFile(f,f)} should return {@code true}.
1508 * <li>It is <i>symmetric</i>: for two {@code Paths} {@code f} and {@code g},
1509 * {@code isSameFile(f,g)} will equal {@code isSameFile(g,f)}.
1510 * <li>It is <i>transitive</i>: for three {@code Paths}
1511 * {@code f}, {@code g}, and {@code h}, if {@code isSameFile(f,g)} returns
1512 * {@code true} and {@code isSameFile(g,h)} returns {@code true}, then
1513 * {@code isSameFile(f,h)} will return {@code true}.
1514 * </ul>
1515 *
1516 * @param path
1517 * one path to the file
1518 * @param path2
1519 * the other path
1520 *
1521 * @return {@code true} if, and only if, the two paths locate the same file
1522 *
1523 * @throws IOException
1524 * if an I/O error occurs
1525 * @throws SecurityException
1526 * In the case of the default provider, and a security manager is
1527 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1528 * method is invoked to check read access to both files.
1529 *
1530 * @see java.nio.file.attribute.BasicFileAttributes#fileKey
1531 */
1532 public static boolean isSameFile(Path path, Path path2) throws IOException {
1533 return provider(path).isSameFile(path, path2);
1534 }
1535
1536 /**
1537 * Finds and returns the position of the first mismatched byte in the content
1538 * of two files, or {@code -1L} if there is no mismatch. The position will be
1539 * in the inclusive range of {@code 0L} up to the size (in bytes) of the
1540 * smaller file.
1541 *
1542 * <p> Two files are considered to match if they satisfy one of the following
1543 * conditions:
1544 * <ul>
1545 * <li> The two paths locate the {@linkplain #isSameFile(Path, Path) same file},
1546 * even if two {@linkplain Path#equals(Object) equal} paths locate a file
1547 * does not exist, or </li>
1548 * <li> The two files are the same size, and every byte in the first file
1549 * is identical to the corresponding byte in the second file. </li>
1550 * </ul>
1551 *
1552 * <p> Otherwise there is a mismatch between the two files and the value
1553 * returned by this method is:
1554 * <ul>
1555 * <li> The position of the first mismatched byte, or </li>
1556 * <li> The size of the smaller file (in bytes) when the files are different
1557 * sizes and every byte of the smaller file is identical to the
1558 * corresponding byte of the larger file. </li>
1559 * </ul>
1560 *
1561 * <p> This method may not be atomic with respect to other file system
1562 * operations. This method is always <i>reflexive</i> (for {@code Path f},
1563 * {@code mismatch(f,f)} returns {@code -1L}). If the file system and files
1564 * remain static, then this method is <i>symmetric</i> (for two {@code Paths f}
1565 * and {@code g}, {@code mismatch(f,g)} will return the same value as
1566 * {@code mismatch(g,f)}).
1567 *
1568 * @param path
1569 * the path to the first file
1570 * @param path2
1571 * the path to the second file
1572 *
1573 * @return the position of the first mismatch or {@code -1L} if no mismatch
1574 *
1575 * @throws IOException
1576 * if an I/O error occurs
1577 * @throws SecurityException
1578 * In the case of the default provider, and a security manager is
1579 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1580 * method is invoked to check read access to both files.
1581 *
1582 * @since 12
1583 */
1584 public static long mismatch(Path path, Path path2) throws IOException {
1585 if (isSameFile(path, path2)) {
1586 return -1;
1587 }
1588 byte[] buffer1 = new byte[BUFFER_SIZE];
1589 byte[] buffer2 = new byte[BUFFER_SIZE];
1590 try (InputStream in1 = Files.newInputStream(path);
1591 InputStream in2 = Files.newInputStream(path2);) {
1592 long totalRead = 0;
1593 while (true) {
1594 int nRead1 = in1.readNBytes(buffer1, 0, BUFFER_SIZE);
1595 int nRead2 = in2.readNBytes(buffer2, 0, BUFFER_SIZE);
1596
1597 int i = Arrays.mismatch(buffer1, 0, nRead1, buffer2, 0, nRead2);
1598 if (i > -1) {
1599 return totalRead + i;
1600 }
1601 if (nRead1 < BUFFER_SIZE) {
1602 // we've reached the end of the files, but found no mismatch
1603 return -1;
1604 }
1605 totalRead += nRead1;
1606 }
1607 }
1608 }
1609
1610 /**
1611 * Tells whether or not a file is considered <em>hidden</em>.
1612 *
1613 * @apiNote
1614 * The exact definition of hidden is platform or provider dependent. On UNIX
1615 * for example a file is considered to be hidden if its name begins with a
1616 * period character ('.'). On Windows a file is considered hidden if the DOS
1617 * {@link DosFileAttributes#isHidden hidden} attribute is set.
1618 *
1619 * <p> Depending on the implementation this method may require to access
1620 * the file system to determine if the file is considered hidden.
1621 *
1622 * @param path
1623 * the path to the file to test
1624 *
1625 * @return {@code true} if the file is considered hidden
1626 *
1627 * @throws IOException
1628 * if an I/O error occurs
1629 * @throws SecurityException
1630 * In the case of the default provider, and a security manager is
1631 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1632 * method is invoked to check read access to the file.
1633 */
1634 public static boolean isHidden(Path path) throws IOException {
1635 return provider(path).isHidden(path);
1636 }
1637
1638 // lazy loading of default and installed file type detectors
1639 private static class FileTypeDetectors{
1640 static final FileTypeDetector defaultFileTypeDetector =
1641 createDefaultFileTypeDetector();
1642 static final List<FileTypeDetector> installedDetectors =
1643 loadInstalledDetectors();
1644
1645 // creates the default file type detector
1646 private static FileTypeDetector createDefaultFileTypeDetector() {
1647 return AccessController
1648 .doPrivileged(new PrivilegedAction<>() {
1649 @Override public FileTypeDetector run() {
1650 return sun.nio.fs.DefaultFileTypeDetector.create();
1651 }});
1652 }
1653
1654 // loads all installed file type detectors
1655 private static List<FileTypeDetector> loadInstalledDetectors() {
1656 return AccessController
1657 .doPrivileged(new PrivilegedAction<>() {
1658 @Override public List<FileTypeDetector> run() {
1659 List<FileTypeDetector> list = new ArrayList<>();
1660 ServiceLoader<FileTypeDetector> loader = ServiceLoader
1661 .load(FileTypeDetector.class, ClassLoader.getSystemClassLoader());
1662 for (FileTypeDetector detector: loader) {
1663 list.add(detector);
1664 }
1665 return list;
1666 }});
1667 }
1668 }
1669
1670 /**
1671 * Probes the content type of a file.
1672 *
1673 * <p> This method uses the installed {@link FileTypeDetector} implementations
1674 * to probe the given file to determine its content type. Each file type
1675 * detector's {@link FileTypeDetector#probeContentType probeContentType} is
1676 * invoked, in turn, to probe the file type. If the file is recognized then
1677 * the content type is returned. If the file is not recognized by any of the
1678 * installed file type detectors then a system-default file type detector is
1679 * invoked to guess the content type.
1680 *
1681 * <p> A given invocation of the Java virtual machine maintains a system-wide
1682 * list of file type detectors. Installed file type detectors are loaded
1683 * using the service-provider loading facility defined by the {@link ServiceLoader}
1684 * class. Installed file type detectors are loaded using the system class
1685 * loader. If the system class loader cannot be found then the platform class
1686 * loader is used. File type detectors are typically installed
1687 * by placing them in a JAR file on the application class path,
1688 * the JAR file contains a provider-configuration file
1689 * named {@code java.nio.file.spi.FileTypeDetector} in the resource directory
1690 * {@code META-INF/services}, and the file lists one or more fully-qualified
1691 * names of concrete subclass of {@code FileTypeDetector } that have a zero
1692 * argument constructor. If the process of locating or instantiating the
1693 * installed file type detectors fails then an unspecified error is thrown.
1694 * The ordering that installed providers are located is implementation
1695 * specific.
1696 *
1697 * <p> The return value of this method is the string form of the value of a
1698 * Multipurpose Internet Mail Extension (MIME) content type as
1699 * defined by <a href="http://www.ietf.org/rfc/rfc2045.txt"><i>RFC 2045:
1700 * Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet
1701 * Message Bodies</i></a>. The string is guaranteed to be parsable according
1702 * to the grammar in the RFC.
1703 *
1704 * @param path
1705 * the path to the file to probe
1706 *
1707 * @return The content type of the file, or {@code null} if the content
1708 * type cannot be determined
1709 *
1710 * @throws IOException
1711 * if an I/O error occurs
1712 * @throws SecurityException
1713 * If a security manager is installed and it denies an unspecified
1714 * permission required by a file type detector implementation.
1715 */
1716 public static String probeContentType(Path path)
1717 throws IOException
1718 {
1719 // try installed file type detectors
1720 for (FileTypeDetector detector: FileTypeDetectors.installedDetectors) {
1721 String result = detector.probeContentType(path);
1722 if (result != null)
1723 return result;
1724 }
1725
1726 // fallback to default
1727 return FileTypeDetectors.defaultFileTypeDetector.probeContentType(path);
1728 }
1729
1730 // -- File Attributes --
1731
1732 /**
1733 * Returns a file attribute view of a given type.
1734 *
1735 * <p> A file attribute view provides a read-only or updatable view of a
1736 * set of file attributes. This method is intended to be used where the file
1737 * attribute view defines type-safe methods to read or update the file
1738 * attributes. The {@code type} parameter is the type of the attribute view
1739 * required and the method returns an instance of that type if supported.
1740 * The {@link BasicFileAttributeView} type supports access to the basic
1741 * attributes of a file. Invoking this method to select a file attribute
1742 * view of that type will always return an instance of that class.
1743 *
1744 * <p> The {@code options} array may be used to indicate how symbolic links
1745 * are handled by the resulting file attribute view for the case that the
1746 * file is a symbolic link. By default, symbolic links are followed. If the
1747 * option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is present then
1748 * symbolic links are not followed. This option is ignored by implementations
1749 * that do not support symbolic links.
1750 *
1751 * <p> <b>Usage Example:</b>
1752 * Suppose we want read or set a file's ACL, if supported:
1753 * <pre>
1754 * Path path = ...
1755 * AclFileAttributeView view = Files.getFileAttributeView(path, AclFileAttributeView.class);
1756 * if (view != null) {
1757 * List<AclEntry> acl = view.getAcl();
1758 * :
1759 * }
1760 * </pre>
1761 *
1762 * @param <V>
1763 * The {@code FileAttributeView} type
1764 * @param path
1765 * the path to the file
1766 * @param type
1767 * the {@code Class} object corresponding to the file attribute view
1768 * @param options
1769 * options indicating how symbolic links are handled
1770 *
1771 * @return a file attribute view of the specified type, or {@code null} if
1772 * the attribute view type is not available
1773 */
1774 public static <V extends FileAttributeView> V getFileAttributeView(Path path,
1775 Class<V> type,
1776 LinkOption... options)
1777 {
1778 return provider(path).getFileAttributeView(path, type, options);
1779 }
1780
1781 /**
1782 * Reads a file's attributes as a bulk operation.
1783 *
1784 * <p> The {@code type} parameter is the type of the attributes required
1785 * and this method returns an instance of that type if supported. All
1786 * implementations support a basic set of file attributes and so invoking
1787 * this method with a {@code type} parameter of {@code
1788 * BasicFileAttributes.class} will not throw {@code
1789 * UnsupportedOperationException}.
1790 *
1791 * <p> The {@code options} array may be used to indicate how symbolic links
1792 * are handled for the case that the file is a symbolic link. By default,
1793 * symbolic links are followed and the file attribute of the final target
1794 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1795 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1796 *
1797 * <p> It is implementation specific if all file attributes are read as an
1798 * atomic operation with respect to other file system operations.
1799 *
1800 * <p> <b>Usage Example:</b>
1801 * Suppose we want to read a file's attributes in bulk:
1802 * <pre>
1803 * Path path = ...
1804 * BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class);
1805 * </pre>
1806 * Alternatively, suppose we want to read file's POSIX attributes without
1807 * following symbolic links:
1808 * <pre>
1809 * PosixFileAttributes attrs =
1810 * Files.readAttributes(path, PosixFileAttributes.class, NOFOLLOW_LINKS);
1811 * </pre>
1812 *
1813 * @param <A>
1814 * The {@code BasicFileAttributes} type
1815 * @param path
1816 * the path to the file
1817 * @param type
1818 * the {@code Class} of the file attributes required
1819 * to read
1820 * @param options
1821 * options indicating how symbolic links are handled
1822 *
1823 * @return the file attributes
1824 *
1825 * @throws UnsupportedOperationException
1826 * if an attributes of the given type are not supported
1827 * @throws IOException
1828 * if an I/O error occurs
1829 * @throws SecurityException
1830 * In the case of the default provider, a security manager is
1831 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1832 * method is invoked to check read access to the file. If this
1833 * method is invoked to read security sensitive attributes then the
1834 * security manager may be invoke to check for additional permissions.
1835 */
1836 public static <A extends BasicFileAttributes> A readAttributes(Path path,
1837 Class<A> type,
1838 LinkOption... options)
1839 throws IOException
1840 {
1841 return provider(path).readAttributes(path, type, options);
1842 }
1843
1844 /**
1845 * Sets the value of a file attribute.
1846 *
1847 * <p> The {@code attribute} parameter identifies the attribute to be set
1848 * and takes the form:
1849 * <blockquote>
1850 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
1851 * </blockquote>
1852 * where square brackets [...] delineate an optional component and the
1853 * character {@code ':'} stands for itself.
1854 *
1855 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1856 * FileAttributeView} that identifies a set of file attributes. If not
1857 * specified then it defaults to {@code "basic"}, the name of the file
1858 * attribute view that identifies the basic set of file attributes common to
1859 * many file systems. <i>attribute-name</i> is the name of the attribute
1860 * within the set.
1861 *
1862 * <p> The {@code options} array may be used to indicate how symbolic links
1863 * are handled for the case that the file is a symbolic link. By default,
1864 * symbolic links are followed and the file attribute of the final target
1865 * of the link is set. If the option {@link LinkOption#NOFOLLOW_LINKS
1866 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1867 *
1868 * <p> <b>Usage Example:</b>
1869 * Suppose we want to set the DOS "hidden" attribute:
1870 * <pre>
1871 * Path path = ...
1872 * Files.setAttribute(path, "dos:hidden", true);
1873 * </pre>
1874 *
1875 * @param path
1876 * the path to the file
1877 * @param attribute
1878 * the attribute to set
1879 * @param value
1880 * the attribute value
1881 * @param options
1882 * options indicating how symbolic links are handled
1883 *
1884 * @return the given path
1885 *
1886 * @throws UnsupportedOperationException
1887 * if the attribute view is not available
1888 * @throws IllegalArgumentException
1889 * if the attribute name is not specified, or is not recognized, or
1890 * the attribute value is of the correct type but has an
1891 * inappropriate value
1892 * @throws ClassCastException
1893 * if the attribute value is not of the expected type or is a
1894 * collection containing elements that are not of the expected
1895 * type
1896 * @throws IOException
1897 * if an I/O error occurs
1898 * @throws SecurityException
1899 * In the case of the default provider, and a security manager is
1900 * installed, its {@link SecurityManager#checkWrite(String) checkWrite}
1901 * method denies write access to the file. If this method is invoked
1902 * to set security sensitive attributes then the security manager
1903 * may be invoked to check for additional permissions.
1904 */
1905 public static Path setAttribute(Path path, String attribute, Object value,
1906 LinkOption... options)
1907 throws IOException
1908 {
1909 provider(path).setAttribute(path, attribute, value, options);
1910 return path;
1911 }
1912
1913 /**
1914 * Reads the value of a file attribute.
1915 *
1916 * <p> The {@code attribute} parameter identifies the attribute to be read
1917 * and takes the form:
1918 * <blockquote>
1919 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
1920 * </blockquote>
1921 * where square brackets [...] delineate an optional component and the
1922 * character {@code ':'} stands for itself.
1923 *
1924 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1925 * FileAttributeView} that identifies a set of file attributes. If not
1926 * specified then it defaults to {@code "basic"}, the name of the file
1927 * attribute view that identifies the basic set of file attributes common to
1928 * many file systems. <i>attribute-name</i> is the name of the attribute.
1929 *
1930 * <p> The {@code options} array may be used to indicate how symbolic links
1931 * are handled for the case that the file is a symbolic link. By default,
1932 * symbolic links are followed and the file attribute of the final target
1933 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1934 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1935 *
1936 * <p> <b>Usage Example:</b>
1937 * Suppose we require the user ID of the file owner on a system that
1938 * supports a "{@code unix}" view:
1939 * <pre>
1940 * Path path = ...
1941 * int uid = (Integer)Files.getAttribute(path, "unix:uid");
1942 * </pre>
1943 *
1944 * @param path
1945 * the path to the file
1946 * @param attribute
1947 * the attribute to read
1948 * @param options
1949 * options indicating how symbolic links are handled
1950 *
1951 * @return the attribute value
1952 *
1953 * @throws UnsupportedOperationException
1954 * if the attribute view is not available
1955 * @throws IllegalArgumentException
1956 * if the attribute name is not specified or is not recognized
1957 * @throws IOException
1958 * if an I/O error occurs
1959 * @throws SecurityException
1960 * In the case of the default provider, and a security manager is
1961 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1962 * method denies read access to the file. If this method is invoked
1963 * to read security sensitive attributes then the security manager
1964 * may be invoked to check for additional permissions.
1965 */
1966 public static Object getAttribute(Path path, String attribute,
1967 LinkOption... options)
1968 throws IOException
1969 {
1970 // only one attribute should be read
1971 if (attribute.indexOf('*') >= 0 || attribute.indexOf(',') >= 0)
1972 throw new IllegalArgumentException(attribute);
1973 Map<String,Object> map = readAttributes(path, attribute, options);
1974 assert map.size() == 1;
1975 String name;
1976 int pos = attribute.indexOf(':');
1977 if (pos == -1) {
1978 name = attribute;
1979 } else {
1980 name = (pos == attribute.length()) ? "" : attribute.substring(pos+1);
1981 }
1982 return map.get(name);
1983 }
1984
1985 /**
1986 * Reads a set of file attributes as a bulk operation.
1987 *
1988 * <p> The {@code attributes} parameter identifies the attributes to be read
1989 * and takes the form:
1990 * <blockquote>
1991 * [<i>view-name</i><b>:</b>]<i>attribute-list</i>
1992 * </blockquote>
1993 * where square brackets [...] delineate an optional component and the
1994 * character {@code ':'} stands for itself.
1995 *
1996 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1997 * FileAttributeView} that identifies a set of file attributes. If not
1998 * specified then it defaults to {@code "basic"}, the name of the file
1999 * attribute view that identifies the basic set of file attributes common to
2000 * many file systems.
2001 *
2002 * <p> The <i>attribute-list</i> component is a comma separated list of
2003 * one or more names of attributes to read. If the list contains the value
2004 * {@code "*"} then all attributes are read. Attributes that are not supported
2005 * are ignored and will not be present in the returned map. It is
2006 * implementation specific if all attributes are read as an atomic operation
2007 * with respect to other file system operations.
2008 *
2009 * <p> The following examples demonstrate possible values for the {@code
2010 * attributes} parameter:
2011 *
2012 * <table class="striped" style="text-align: left; margin-left:2em">
2013 * <caption style="display:none">Possible values</caption>
2014 * <thead>
2015 * <tr>
2016 * <th scope="col">Example
2017 * <th scope="col">Description
2018 * </thead>
2019 * <tbody>
2020 * <tr>
2021 * <th scope="row"> {@code "*"} </th>
2022 * <td> Read all {@link BasicFileAttributes basic-file-attributes}. </td>
2023 * </tr>
2024 * <tr>
2025 * <th scope="row"> {@code "size,lastModifiedTime,lastAccessTime"} </th>
2026 * <td> Reads the file size, last modified time, and last access time
2027 * attributes. </td>
2028 * </tr>
2029 * <tr>
2030 * <th scope="row"> {@code "posix:*"} </th>
2031 * <td> Read all {@link PosixFileAttributes POSIX-file-attributes}. </td>
2032 * </tr>
2033 * <tr>
2034 * <th scope="row"> {@code "posix:permissions,owner,size"} </th>
2035 * <td> Reads the POSIX file permissions, owner, and file size. </td>
2036 * </tr>
2037 * </tbody>
2038 * </table>
2039 *
2040 * <p> The {@code options} array may be used to indicate how symbolic links
2041 * are handled for the case that the file is a symbolic link. By default,
2042 * symbolic links are followed and the file attribute of the final target
2043 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2044 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2045 *
2046 * @param path
2047 * the path to the file
2048 * @param attributes
2049 * the attributes to read
2050 * @param options
2051 * options indicating how symbolic links are handled
2052 *
2053 * @return a map of the attributes returned; The map's keys are the
2054 * attribute names, its values are the attribute values
2055 *
2056 * @throws UnsupportedOperationException
2057 * if the attribute view is not available
2058 * @throws IllegalArgumentException
2059 * if no attributes are specified or an unrecognized attribute is
2060 * specified
2061 * @throws IOException
2062 * if an I/O error occurs
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. If this method is invoked
2067 * to read security sensitive attributes then the security manager
2068 * may be invoke to check for additional permissions.
2069 */
2070 public static Map<String,Object> readAttributes(Path path, String attributes,
2071 LinkOption... options)
2072 throws IOException
2073 {
2074 return provider(path).readAttributes(path, attributes, options);
2075 }
2076
2077 /**
2078 * Returns a file's POSIX file permissions.
2079 *
2080 * <p> The {@code path} parameter is associated with a {@code FileSystem}
2081 * that supports the {@link PosixFileAttributeView}. This attribute view
2082 * provides access to file attributes commonly associated with files on file
2083 * systems used by operating systems that implement the Portable Operating
2084 * System Interface (POSIX) family of standards.
2085 *
2086 * <p> The {@code options} array may be used to indicate how symbolic links
2087 * are handled for the case that the file is a symbolic link. By default,
2088 * symbolic links are followed and the file attribute of the final target
2089 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2090 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2091 *
2092 * @param path
2093 * the path to the file
2094 * @param options
2095 * options indicating how symbolic links are handled
2096 *
2097 * @return the file permissions
2098 *
2099 * @throws UnsupportedOperationException
2100 * if the associated file system does not support the {@code
2101 * PosixFileAttributeView}
2102 * @throws IOException
2103 * if an I/O error occurs
2104 * @throws SecurityException
2105 * In the case of the default provider, a security manager is
2106 * installed, and it denies
2107 * {@link RuntimePermission}{@code ("accessUserInformation")}
2108 * or its {@link SecurityManager#checkRead(String) checkRead} method
2109 * denies read access to the file.
2110 */
2111 public static Set<PosixFilePermission> getPosixFilePermissions(Path path,
2112 LinkOption... options)
2113 throws IOException
2114 {
2115 return readAttributes(path, PosixFileAttributes.class, options).permissions();
2116 }
2117
2118 /**
2119 * Sets a file's POSIX permissions.
2120 *
2121 * <p> The {@code path} parameter is associated with a {@code FileSystem}
2122 * that supports the {@link PosixFileAttributeView}. This attribute view
2123 * provides access to file attributes commonly associated with files on file
2124 * systems used by operating systems that implement the Portable Operating
2125 * System Interface (POSIX) family of standards.
2126 *
2127 * @param path
2128 * The path to the file
2129 * @param perms
2130 * The new set of permissions
2131 *
2132 * @return The given path
2133 *
2134 * @throws UnsupportedOperationException
2135 * if the associated file system does not support the {@code
2136 * PosixFileAttributeView}
2137 * @throws ClassCastException
2138 * if the sets contains elements that are not of type {@code
2139 * PosixFilePermission}
2140 * @throws IOException
2141 * if an I/O error occurs
2142 * @throws SecurityException
2143 * In the case of the default provider, and a security manager is
2144 * installed, it denies
2145 * {@link RuntimePermission}{@code ("accessUserInformation")}
2146 * or its {@link SecurityManager#checkWrite(String) checkWrite}
2147 * method denies write access to the file.
2148 */
2149 public static Path setPosixFilePermissions(Path path,
2150 Set<PosixFilePermission> perms)
2151 throws IOException
2152 {
2153 PosixFileAttributeView view =
2154 getFileAttributeView(path, PosixFileAttributeView.class);
2155 if (view == null)
2156 throw new UnsupportedOperationException();
2157 view.setPermissions(perms);
2158 return path;
2159 }
2160
2161 /**
2162 * Returns the owner of a file.
2163 *
2164 * <p> The {@code path} parameter is associated with a file system that
2165 * supports {@link FileOwnerAttributeView}. This file attribute view provides
2166 * access to a file attribute that is the owner of the file.
2167 *
2168 * @param path
2169 * The path to the file
2170 * @param options
2171 * options indicating how symbolic links are handled
2172 *
2173 * @return A user principal representing the owner of the file
2174 *
2175 * @throws UnsupportedOperationException
2176 * if the associated file system does not support the {@code
2177 * FileOwnerAttributeView}
2178 * @throws IOException
2179 * if an I/O error occurs
2180 * @throws SecurityException
2181 * In the case of the default provider, and a security manager is
2182 * installed, it denies
2183 * {@link RuntimePermission}{@code ("accessUserInformation")}
2184 * or its {@link SecurityManager#checkRead(String) checkRead} method
2185 * denies read access to the file.
2186 */
2187 public static UserPrincipal getOwner(Path path, LinkOption... options) throws IOException {
2188 FileOwnerAttributeView view =
2189 getFileAttributeView(path, FileOwnerAttributeView.class, options);
2190 if (view == null)
2191 throw new UnsupportedOperationException();
2192 return view.getOwner();
2193 }
2194
2195 /**
2196 * Updates the file owner.
2197 *
2198 * <p> The {@code path} parameter is associated with a file system that
2199 * supports {@link FileOwnerAttributeView}. This file attribute view provides
2200 * access to a file attribute that is the owner of the file.
2201 *
2202 * <p> <b>Usage Example:</b>
2203 * Suppose we want to make "joe" the owner of a file:
2204 * <pre>
2205 * Path path = ...
2206 * UserPrincipalLookupService lookupService =
2207 * provider(path).getUserPrincipalLookupService();
2208 * UserPrincipal joe = lookupService.lookupPrincipalByName("joe");
2209 * Files.setOwner(path, joe);
2210 * </pre>
2211 *
2212 * @param path
2213 * The path to the file
2214 * @param owner
2215 * The new file owner
2216 *
2217 * @return The given path
2218 *
2219 * @throws UnsupportedOperationException
2220 * if the associated file system does not support the {@code
2221 * FileOwnerAttributeView}
2222 * @throws IOException
2223 * if an I/O error occurs
2224 * @throws SecurityException
2225 * In the case of the default provider, and a security manager is
2226 * installed, it denies
2227 * {@link RuntimePermission}{@code ("accessUserInformation")}
2228 * or its {@link SecurityManager#checkWrite(String) checkWrite}
2229 * method denies write access to the file.
2230 *
2231 * @see FileSystem#getUserPrincipalLookupService
2232 * @see java.nio.file.attribute.UserPrincipalLookupService
2233 */
2234 public static Path setOwner(Path path, UserPrincipal owner)
2235 throws IOException
2236 {
2237 FileOwnerAttributeView view =
2238 getFileAttributeView(path, FileOwnerAttributeView.class);
2239 if (view == null)
2240 throw new UnsupportedOperationException();
2241 view.setOwner(owner);
2242 return path;
2243 }
2244
2245 /**
2246 * Tests whether a file is a symbolic link.
2247 *
2248 * <p> Where it is required to distinguish an I/O exception from the case
2249 * that the file is not a symbolic link then the file attributes can be
2250 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2251 * readAttributes} method and the file type tested with the {@link
2252 * BasicFileAttributes#isSymbolicLink} method.
2253 *
2254 * @param path The path to the file
2255 *
2256 * @return {@code true} if the file is a symbolic link; {@code false} if
2257 * the file does not exist, is not a symbolic link, or it cannot
2258 * be determined if the file is a symbolic link or not.
2259 *
2260 * @throws SecurityException
2261 * In the case of the default provider, and a security manager is
2262 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2263 * method denies read access to the file.
2264 */
2265 public static boolean isSymbolicLink(Path path) {
2266 try {
2267 return readAttributes(path,
2268 BasicFileAttributes.class,
2269 LinkOption.NOFOLLOW_LINKS).isSymbolicLink();
2270 } catch (IOException ioe) {
2271 return false;
2272 }
2273 }
2274
2275 /**
2276 * Tests whether a file is a directory.
2277 *
2278 * <p> The {@code options} array may be used to indicate how symbolic links
2279 * are handled for the case that the file is a symbolic link. By default,
2280 * symbolic links are followed and the file attribute of the final target
2281 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2282 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2283 *
2284 * <p> Where it is required to distinguish an I/O exception from the case
2285 * that the file is not a directory then the file attributes can be
2286 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2287 * readAttributes} method and the file type tested with the {@link
2288 * BasicFileAttributes#isDirectory} method.
2289 *
2290 * @param path
2291 * the path to the file to test
2292 * @param options
2293 * options indicating how symbolic links are handled
2294 *
2295 * @return {@code true} if the file is a directory; {@code false} if
2296 * the file does not exist, is not a directory, or it cannot
2297 * be determined if the file is a directory or not.
2298 *
2299 * @throws SecurityException
2300 * In the case of the default provider, and a security manager is
2301 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2302 * method denies read access to the file.
2303 */
2304 public static boolean isDirectory(Path path, LinkOption... options) {
2305 if (options.length == 0) {
2306 FileSystemProvider provider = provider(path);
2307 if (provider instanceof AbstractFileSystemProvider)
2308 return ((AbstractFileSystemProvider)provider).isDirectory(path);
2309 }
2310
2311 try {
2312 return readAttributes(path, BasicFileAttributes.class, options).isDirectory();
2313 } catch (IOException ioe) {
2314 return false;
2315 }
2316 }
2317
2318 /**
2319 * Tests whether a file is a regular file with opaque content.
2320 *
2321 * <p> The {@code options} array may be used to indicate how symbolic links
2322 * are handled for the case that the file is a symbolic link. By default,
2323 * symbolic links are followed and the file attribute of the final target
2324 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2325 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2326 *
2327 * <p> Where it is required to distinguish an I/O exception from the case
2328 * that the file is not a regular file then the file attributes can be
2329 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2330 * readAttributes} method and the file type tested with the {@link
2331 * BasicFileAttributes#isRegularFile} method.
2332 *
2333 * @param path
2334 * the path to the file
2335 * @param options
2336 * options indicating how symbolic links are handled
2337 *
2338 * @return {@code true} if the file is a regular file; {@code false} if
2339 * the file does not exist, is not a regular file, or it
2340 * cannot be determined if the file is a regular file or not.
2341 *
2342 * @throws SecurityException
2343 * In the case of the default provider, and a security manager is
2344 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2345 * method denies read access to the file.
2346 */
2347 public static boolean isRegularFile(Path path, LinkOption... options) {
2348 if (options.length == 0) {
2349 FileSystemProvider provider = provider(path);
2350 if (provider instanceof AbstractFileSystemProvider)
2351 return ((AbstractFileSystemProvider)provider).isRegularFile(path);
2352 }
2353
2354 try {
2355 return readAttributes(path, BasicFileAttributes.class, options).isRegularFile();
2356 } catch (IOException ioe) {
2357 return false;
2358 }
2359 }
2360
2361 /**
2362 * Returns a file's last modified time.
2363 *
2364 * <p> The {@code options} array may be used to indicate how symbolic links
2365 * are handled for the case that the file is a symbolic link. By default,
2366 * symbolic links are followed and the file attribute of the final target
2367 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2368 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2369 *
2370 * @param path
2371 * the path to the file
2372 * @param options
2373 * options indicating how symbolic links are handled
2374 *
2375 * @return a {@code FileTime} representing the time the file was last
2376 * modified, or an implementation specific default when a time
2377 * stamp to indicate the time of last modification is not supported
2378 * by the file system
2379 *
2380 * @throws IOException
2381 * if an I/O error occurs
2382 * @throws SecurityException
2383 * In the case of the default provider, and a security manager is
2384 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2385 * method denies read access to the file.
2386 *
2387 * @see BasicFileAttributes#lastModifiedTime
2388 */
2389 public static FileTime getLastModifiedTime(Path path, LinkOption... options)
2390 throws IOException
2391 {
2392 return readAttributes(path, BasicFileAttributes.class, options).lastModifiedTime();
2393 }
2394
2395 /**
2396 * Updates a file's last modified time attribute. The file time is converted
2397 * to the epoch and precision supported by the file system. Converting from
2398 * finer to coarser granularities result in precision loss. The behavior of
2399 * this method when attempting to set the last modified time when it is not
2400 * supported by the file system or is outside the range supported by the
2401 * underlying file store is not defined. It may or not fail by throwing an
2402 * {@code IOException}.
2403 *
2404 * <p> <b>Usage Example:</b>
2405 * Suppose we want to set the last modified time to the current time:
2406 * <pre>
2407 * Path path = ...
2408 * FileTime now = FileTime.fromMillis(System.currentTimeMillis());
2409 * Files.setLastModifiedTime(path, now);
2410 * </pre>
2411 *
2412 * @param path
2413 * the path to the file
2414 * @param time
2415 * the new last modified time
2416 *
2417 * @return the given path
2418 *
2419 * @throws IOException
2420 * if an I/O error occurs
2421 * @throws SecurityException
2422 * In the case of the default provider, and a security manager is
2423 * installed, its {@link SecurityManager#checkWrite(String)
2424 * checkWrite} method denies write access to the file.
2425 *
2426 * @see BasicFileAttributeView#setTimes
2427 */
2428 public static Path setLastModifiedTime(Path path, FileTime time)
2429 throws IOException
2430 {
2431 getFileAttributeView(path, BasicFileAttributeView.class)
2432 .setTimes(Objects.requireNonNull(time), null, null);
2433 return path;
2434 }
2435
2436 /**
2437 * Returns the size of a file (in bytes). The size may differ from the
2438 * actual size on the file system due to compression, support for sparse
2439 * files, or other reasons. The size of files that are not {@link
2440 * #isRegularFile regular} files is implementation specific and
2441 * therefore unspecified.
2442 *
2443 * @param path
2444 * the path to the file
2445 *
2446 * @return the file size, in bytes
2447 *
2448 * @throws IOException
2449 * if an I/O error occurs
2450 * @throws SecurityException
2451 * In the case of the default provider, and a security manager is
2452 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2453 * method denies read access to the file.
2454 *
2455 * @see BasicFileAttributes#size
2456 */
2457 public static long size(Path path) throws IOException {
2458 return readAttributes(path, BasicFileAttributes.class).size();
2459 }
2460
2461 // -- Accessibility --
2462
2463 /**
2464 * Returns {@code false} if NOFOLLOW_LINKS is present.
2465 */
2466 private static boolean followLinks(LinkOption... options) {
2467 boolean followLinks = true;
2468 for (LinkOption opt: options) {
2469 if (opt == LinkOption.NOFOLLOW_LINKS) {
2470 followLinks = false;
2471 continue;
2472 }
2473 if (opt == null)
2474 throw new NullPointerException();
2475 throw new AssertionError("Should not get here");
2476 }
2477 return followLinks;
2478 }
2479
2480 /**
2481 * Tests whether a file exists.
2482 *
2483 * <p> The {@code options} parameter may be used to indicate how symbolic links
2484 * are handled for the case that the file is a symbolic link. By default,
2485 * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
2486 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2487 *
2488 * <p> Note that the result of this method is immediately outdated. If this
2489 * method indicates the file exists then there is no guarantee that a
2490 * subsequent access will succeed. Care should be taken when using this
2491 * method in security sensitive applications.
2492 *
2493 * @param path
2494 * the path to the file to test
2495 * @param options
2496 * options indicating how symbolic links are handled
2497 * .
2498 * @return {@code true} if the file exists; {@code false} if the file does
2499 * not exist or its existence cannot be determined.
2500 *
2501 * @throws SecurityException
2502 * In the case of the default provider, the {@link
2503 * SecurityManager#checkRead(String)} is invoked to check
2504 * read access to the file.
2505 *
2506 * @see #notExists
2507 */
2508 public static boolean exists(Path path, LinkOption... options) {
2509 if (options.length == 0) {
2510 FileSystemProvider provider = provider(path);
2511 if (provider instanceof AbstractFileSystemProvider)
2512 return ((AbstractFileSystemProvider)provider).exists(path);
2513 }
2514
2515 try {
2516 if (followLinks(options)) {
2517 provider(path).checkAccess(path);
2518 } else {
2519 // attempt to read attributes without following links
2520 readAttributes(path, BasicFileAttributes.class,
2521 LinkOption.NOFOLLOW_LINKS);
2522 }
2523 // file exists
2524 return true;
2525 } catch (IOException x) {
2526 // does not exist or unable to determine if file exists
2527 return false;
2528 }
2529
2530 }
2531
2532 /**
2533 * Tests whether the file located by this path does not exist. This method
2534 * is intended for cases where it is required to take action when it can be
2535 * confirmed that a file does not exist.
2536 *
2537 * <p> The {@code options} parameter may be used to indicate how symbolic links
2538 * are handled for the case that the file is a symbolic link. By default,
2539 * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
2540 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2541 *
2542 * <p> Note that this method is not the complement of the {@link #exists
2543 * exists} method. Where it is not possible to determine if a file exists
2544 * or not then both methods return {@code false}. As with the {@code exists}
2545 * method, the result of this method is immediately outdated. If this
2546 * method indicates the file does exist then there is no guarantee that a
2547 * subsequent attempt to create the file will succeed. Care should be taken
2548 * when using this method in security sensitive applications.
2549 *
2550 * @param path
2551 * the path to the file to test
2552 * @param options
2553 * options indicating how symbolic links are handled
2554 *
2555 * @return {@code true} if the file does not exist; {@code false} if the
2556 * file exists or its existence cannot be determined
2557 *
2558 * @throws SecurityException
2559 * In the case of the default provider, the {@link
2560 * SecurityManager#checkRead(String)} is invoked to check
2561 * read access to the file.
2562 */
2563 public static boolean notExists(Path path, LinkOption... options) {
2564 try {
2565 if (followLinks(options)) {
2566 provider(path).checkAccess(path);
2567 } else {
2568 // attempt to read attributes without following links
2569 readAttributes(path, BasicFileAttributes.class,
2570 LinkOption.NOFOLLOW_LINKS);
2571 }
2572 // file exists
2573 return false;
2574 } catch (NoSuchFileException x) {
2575 // file confirmed not to exist
2576 return true;
2577 } catch (IOException x) {
2578 return false;
2579 }
2580 }
2581
2582 /**
2583 * Used by isReadable, isWritable, isExecutable to test access to a file.
2584 */
2585 private static boolean isAccessible(Path path, AccessMode... modes) {
2586 try {
2587 provider(path).checkAccess(path, modes);
2588 return true;
2589 } catch (IOException x) {
2590 return false;
2591 }
2592 }
2593
2594 /**
2595 * Tests whether a file is readable. This method checks that a file exists
2596 * and that this Java virtual machine has appropriate privileges that would
2597 * allow it open the file for reading. Depending on the implementation, this
2598 * method may require to read file permissions, access control lists, or
2599 * other file attributes in order to check the effective access to the file.
2600 * Consequently, this method may not be atomic with respect to other file
2601 * system operations.
2602 *
2603 * <p> Note that the result of this method is immediately outdated, there is
2604 * no guarantee that a subsequent attempt to open the file for reading will
2605 * succeed (or even that it will access the same file). Care should be taken
2606 * when using this method in security sensitive applications.
2607 *
2608 * @param path
2609 * the path to the file to check
2610 *
2611 * @return {@code true} if the file exists and is readable; {@code false}
2612 * if the file does not exist, read access would be denied because
2613 * the Java virtual machine has insufficient privileges, or access
2614 * cannot be determined
2615 *
2616 * @throws SecurityException
2617 * In the case of the default provider, and a security manager is
2618 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2619 * is invoked to check read access to the file.
2620 */
2621 public static boolean isReadable(Path path) {
2622 return isAccessible(path, AccessMode.READ);
2623 }
2624
2625 /**
2626 * Tests whether a file is writable. This method checks that a file exists
2627 * and that this Java virtual machine has appropriate privileges that would
2628 * allow it open the file for writing. Depending on the implementation, this
2629 * method may require to read file permissions, access control lists, or
2630 * other file attributes in order to check the effective access to the file.
2631 * Consequently, this method may not be atomic with respect to other file
2632 * system operations.
2633 *
2634 * <p> Note that result of this method is immediately outdated, there is no
2635 * guarantee that a subsequent attempt to open the file for writing will
2636 * succeed (or even that it will access the same file). Care should be taken
2637 * when using this method in security sensitive applications.
2638 *
2639 * @param path
2640 * the path to the file to check
2641 *
2642 * @return {@code true} if the file exists and is writable; {@code false}
2643 * if the file does not exist, write access would be denied because
2644 * the Java virtual machine has insufficient privileges, or access
2645 * cannot be determined
2646 *
2647 * @throws SecurityException
2648 * In the case of the default provider, and a security manager is
2649 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2650 * is invoked to check write access to the file.
2651 */
2652 public static boolean isWritable(Path path) {
2653 return isAccessible(path, AccessMode.WRITE);
2654 }
2655
2656 /**
2657 * Tests whether a file is executable. This method checks that a file exists
2658 * and that this Java virtual machine has appropriate privileges to {@link
2659 * Runtime#exec execute} the file. The semantics may differ when checking
2660 * access to a directory. For example, on UNIX systems, checking for
2661 * execute access checks that the Java virtual machine has permission to
2662 * search the directory in order to access file or subdirectories.
2663 *
2664 * <p> Depending on the implementation, this method may require to read file
2665 * permissions, access control lists, or other file attributes in order to
2666 * check the effective access to the file. Consequently, this method may not
2667 * be atomic with respect to other file system operations.
2668 *
2669 * <p> Note that the result of this method is immediately outdated, there is
2670 * no guarantee that a subsequent attempt to execute the file will succeed
2671 * (or even that it will access the same file). Care should be taken when
2672 * using this method in security sensitive applications.
2673 *
2674 * @param path
2675 * the path to the file to check
2676 *
2677 * @return {@code true} if the file exists and is executable; {@code false}
2678 * if the file does not exist, execute access would be denied because
2679 * the Java virtual machine has insufficient privileges, or access
2680 * cannot be determined
2681 *
2682 * @throws SecurityException
2683 * In the case of the default provider, and a security manager is
2684 * installed, the {@link SecurityManager#checkExec(String)
2685 * checkExec} is invoked to check execute access to the file.
2686 */
2687 public static boolean isExecutable(Path path) {
2688 return isAccessible(path, AccessMode.EXECUTE);
2689 }
2690
2691 // -- Recursive operations --
2692
2693 /**
2694 * Walks a file tree.
2695 *
2696 * <p> This method walks a file tree rooted at a given starting file. The
2697 * file tree traversal is <em>depth-first</em> with the given {@link
2698 * FileVisitor} invoked for each file encountered. File tree traversal
2699 * completes when all accessible files in the tree have been visited, or a
2700 * visit method returns a result of {@link FileVisitResult#TERMINATE
2701 * TERMINATE}. Where a visit method terminates due an {@code IOException},
2702 * an uncaught error, or runtime exception, then the traversal is terminated
2703 * and the error or exception is propagated to the caller of this method.
2704 *
2705 * <p> For each file encountered this method attempts to read its {@link
2706 * java.nio.file.attribute.BasicFileAttributes}. If the file is not a
2707 * directory then the {@link FileVisitor#visitFile visitFile} method is
2708 * invoked with the file attributes. If the file attributes cannot be read,
2709 * due to an I/O exception, then the {@link FileVisitor#visitFileFailed
2710 * visitFileFailed} method is invoked with the I/O exception.
2711 *
2712 * <p> Where the file is a directory, and the directory could not be opened,
2713 * then the {@code visitFileFailed} method is invoked with the I/O exception,
2714 * after which, the file tree walk continues, by default, at the next
2715 * <em>sibling</em> of the directory.
2716 *
2717 * <p> Where the directory is opened successfully, then the entries in the
2718 * directory, and their <em>descendants</em> are visited. When all entries
2719 * have been visited, or an I/O error occurs during iteration of the
2720 * directory, then the directory is closed and the visitor's {@link
2721 * FileVisitor#postVisitDirectory postVisitDirectory} method is invoked.
2722 * The file tree walk then continues, by default, at the next <em>sibling</em>
2723 * of the directory.
2724 *
2725 * <p> By default, symbolic links are not automatically followed by this
2726 * method. If the {@code options} parameter contains the {@link
2727 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then symbolic links are
2728 * followed. When following links, and the attributes of the target cannot
2729 * be read, then this method attempts to get the {@code BasicFileAttributes}
2730 * of the link. If they can be read then the {@code visitFile} method is
2731 * invoked with the attributes of the link (otherwise the {@code visitFileFailed}
2732 * method is invoked as specified above).
2733 *
2734 * <p> If the {@code options} parameter contains the {@link
2735 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then this method keeps
2736 * track of directories visited so that cycles can be detected. A cycle
2737 * arises when there is an entry in a directory that is an ancestor of the
2738 * directory. Cycle detection is done by recording the {@link
2739 * java.nio.file.attribute.BasicFileAttributes#fileKey file-key} of directories,
2740 * or if file keys are not available, by invoking the {@link #isSameFile
2741 * isSameFile} method to test if a directory is the same file as an
2742 * ancestor. When a cycle is detected it is treated as an I/O error, and the
2743 * {@link FileVisitor#visitFileFailed visitFileFailed} method is invoked with
2744 * an instance of {@link FileSystemLoopException}.
2745 *
2746 * <p> The {@code maxDepth} parameter is the maximum number of levels of
2747 * directories to visit. A value of {@code 0} means that only the starting
2748 * file is visited, unless denied by the security manager. A value of
2749 * {@link Integer#MAX_VALUE MAX_VALUE} may be used to indicate that all
2750 * levels should be visited. The {@code visitFile} method is invoked for all
2751 * files, including directories, encountered at {@code maxDepth}, unless the
2752 * basic file attributes cannot be read, in which case the {@code
2753 * visitFileFailed} method is invoked.
2754 *
2755 * <p> If a visitor returns a result of {@code null} then {@code
2756 * NullPointerException} is thrown.
2757 *
2758 * <p> When a security manager is installed and it denies access to a file
2759 * (or directory), then it is ignored and the visitor is not invoked for
2760 * that file (or directory).
2761 *
2762 * @param start
2763 * the starting file
2764 * @param options
2765 * options to configure the traversal
2766 * @param maxDepth
2767 * the maximum number of directory levels to visit
2768 * @param visitor
2769 * the file visitor to invoke for each file
2770 *
2771 * @return the starting file
2772 *
2773 * @throws IllegalArgumentException
2774 * if the {@code maxDepth} parameter is negative
2775 * @throws SecurityException
2776 * If the security manager denies access to the starting file.
2777 * In the case of the default provider, the {@link
2778 * SecurityManager#checkRead(String) checkRead} method is invoked
2779 * to check read access to the directory.
2780 * @throws IOException
2781 * if an I/O error is thrown by a visitor method
2782 */
2783 public static Path walkFileTree(Path start,
2784 Set<FileVisitOption> options,
2785 int maxDepth,
2786 FileVisitor<? super Path> visitor)
2787 throws IOException
2788 {
2789 /**
2790 * Create a FileTreeWalker to walk the file tree, invoking the visitor
2791 * for each event.
2792 */
2793 try (FileTreeWalker walker = new FileTreeWalker(options, maxDepth)) {
2794 FileTreeWalker.Event ev = walker.walk(start);
2795 do {
2796 FileVisitResult result;
2797 switch (ev.type()) {
2798 case ENTRY :
2799 IOException ioe = ev.ioeException();
2800 if (ioe == null) {
2801 assert ev.attributes() != null;
2802 result = visitor.visitFile(ev.file(), ev.attributes());
2803 } else {
2804 result = visitor.visitFileFailed(ev.file(), ioe);
2805 }
2806 break;
2807
2808 case START_DIRECTORY :
2809 result = visitor.preVisitDirectory(ev.file(), ev.attributes());
2810
2811 // if SKIP_SIBLINGS and SKIP_SUBTREE is returned then
2812 // there shouldn't be any more events for the current
2813 // directory.
2814 if (result == FileVisitResult.SKIP_SUBTREE ||
2815 result == FileVisitResult.SKIP_SIBLINGS)
2816 walker.pop();
2817 break;
2818
2819 case END_DIRECTORY :
2820 result = visitor.postVisitDirectory(ev.file(), ev.ioeException());
2821
2822 // SKIP_SIBLINGS is a no-op for postVisitDirectory
2823 if (result == FileVisitResult.SKIP_SIBLINGS)
2824 result = FileVisitResult.CONTINUE;
2825 break;
2826
2827 default :
2828 throw new AssertionError("Should not get here");
2829 }
2830
2831 if (Objects.requireNonNull(result) != FileVisitResult.CONTINUE) {
2832 if (result == FileVisitResult.TERMINATE) {
2833 break;
2834 } else if (result == FileVisitResult.SKIP_SIBLINGS) {
2835 walker.skipRemainingSiblings();
2836 }
2837 }
2838 ev = walker.next();
2839 } while (ev != null);
2840 }
2841
2842 return start;
2843 }
2844
2845 /**
2846 * Walks a file tree.
2847 *
2848 * <p> This method works as if invoking it were equivalent to evaluating the
2849 * expression:
2850 * <blockquote><pre>
2851 * walkFileTree(start, EnumSet.noneOf(FileVisitOption.class), Integer.MAX_VALUE, visitor)
2852 * </pre></blockquote>
2853 * In other words, it does not follow symbolic links, and visits all levels
2854 * of the file tree.
2855 *
2856 * @param start
2857 * the starting file
2858 * @param visitor
2859 * the file visitor to invoke for each file
2860 *
2861 * @return the starting file
2862 *
2863 * @throws SecurityException
2864 * If the security manager denies access to the starting file.
2865 * In the case of the default provider, the {@link
2866 * SecurityManager#checkRead(String) checkRead} method is invoked
2867 * to check read access to the directory.
2868 * @throws IOException
2869 * if an I/O error is thrown by a visitor method
2870 */
2871 public static Path walkFileTree(Path start, FileVisitor<? super Path> visitor)
2872 throws IOException
2873 {
2874 return walkFileTree(start,
2875 EnumSet.noneOf(FileVisitOption.class),
2876 Integer.MAX_VALUE,
2877 visitor);
2878 }
2879
2880
2881 // -- Utility methods for simple usages --
2882
2883
2884 /**
2885 * Opens a file for reading, returning a {@code BufferedReader} that may be
2886 * used to read text from the file in an efficient manner. Bytes from the
2887 * file are decoded into characters using the specified charset. Reading
2888 * commences at the beginning of the file.
2889 *
2890 * <p> The {@code Reader} methods that read from the file throw {@code
2891 * IOException} if a malformed or unmappable byte sequence is read.
2892 *
2893 * @param path
2894 * the path to the file
2895 * @param cs
2896 * the charset to use for decoding
2897 *
2898 * @return a new buffered reader, with default buffer size, to read text
2899 * from the file
2900 *
2901 * @throws IOException
2902 * if an I/O error occurs opening the file
2903 * @throws SecurityException
2904 * In the case of the default provider, and a security manager is
2905 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2906 * method is invoked to check read access to the file.
2907 *
2908 * @see #readAllLines
2909 */
2910 public static BufferedReader newBufferedReader(Path path, Charset cs)
2911 throws IOException
2912 {
2913 CharsetDecoder decoder = cs.newDecoder();
2914 Reader reader = new InputStreamReader(newInputStream(path), decoder);
2915 return new BufferedReader(reader);
2916 }
2917
2918 /**
2919 * Opens a file for reading, returning a {@code BufferedReader} to read text
2920 * from the file in an efficient manner. Bytes from the file are decoded into
2921 * characters using the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset
2922 * charset}.
2923 *
2924 * <p> This method works as if invoking it were equivalent to evaluating the
2925 * expression:
2926 * <pre>{@code
2927 * Files.newBufferedReader(path, StandardCharsets.UTF_8)
2928 * }</pre>
2929 *
2930 * @param path
2931 * the path to the file
2932 *
2933 * @return a new buffered reader, with default buffer size, to read text
2934 * from the file
2935 *
2936 * @throws IOException
2937 * if an I/O error occurs opening the file
2938 * @throws SecurityException
2939 * In the case of the default provider, and a security manager is
2940 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2941 * method is invoked to check read access to the file.
2942 *
2943 * @since 1.8
2944 */
2945 public static BufferedReader newBufferedReader(Path path) throws IOException {
2946 return newBufferedReader(path, StandardCharsets.UTF_8);
2947 }
2948
2949 /**
2950 * Opens or creates a file for writing, returning a {@code BufferedWriter}
2951 * that may be used to write text to the file in an efficient manner.
2952 * The {@code options} parameter specifies how the file is created or
2953 * opened. If no options are present then this method works as if the {@link
2954 * StandardOpenOption#CREATE CREATE}, {@link
2955 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
2956 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
2957 * opens the file for writing, creating the file if it doesn't exist, or
2958 * initially truncating an existing {@link #isRegularFile regular-file} to
2959 * a size of {@code 0} if it exists.
2960 *
2961 * <p> The {@code Writer} methods to write text throw {@code IOException}
2962 * if the text cannot be encoded using the specified charset.
2963 *
2964 * @param path
2965 * the path to the file
2966 * @param cs
2967 * the charset to use for encoding
2968 * @param options
2969 * options specifying how the file is opened
2970 *
2971 * @return a new buffered writer, with default buffer size, to write text
2972 * to the file
2973 *
2974 * @throws IllegalArgumentException
2975 * if {@code options} contains an invalid combination of options
2976 * @throws IOException
2977 * if an I/O error occurs opening or creating the file
2978 * @throws UnsupportedOperationException
2979 * if an unsupported option is specified
2980 * @throws SecurityException
2981 * In the case of the default provider, and a security manager is
2982 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2983 * method is invoked to check write access to the file. The {@link
2984 * SecurityManager#checkDelete(String) checkDelete} method is
2985 * invoked to check delete access if the file is opened with the
2986 * {@code DELETE_ON_CLOSE} option.
2987 *
2988 * @see #write(Path,Iterable,Charset,OpenOption[])
2989 */
2990 public static BufferedWriter newBufferedWriter(Path path, Charset cs,
2991 OpenOption... options)
2992 throws IOException
2993 {
2994 CharsetEncoder encoder = cs.newEncoder();
2995 Writer writer = new OutputStreamWriter(newOutputStream(path, options), encoder);
2996 return new BufferedWriter(writer);
2997 }
2998
2999 /**
3000 * Opens or creates a file for writing, returning a {@code BufferedWriter}
3001 * to write text to the file in an efficient manner. The text is encoded
3002 * into bytes for writing using the {@link StandardCharsets#UTF_8 UTF-8}
3003 * {@link Charset charset}.
3004 *
3005 * <p> This method works as if invoking it were equivalent to evaluating the
3006 * expression:
3007 * <pre>{@code
3008 * Files.newBufferedWriter(path, StandardCharsets.UTF_8, options)
3009 * }</pre>
3010 *
3011 * @param path
3012 * the path to the file
3013 * @param options
3014 * options specifying how the file is opened
3015 *
3016 * @return a new buffered writer, with default buffer size, to write text
3017 * to the file
3018 *
3019 * @throws IllegalArgumentException
3020 * if {@code options} contains an invalid combination of options
3021 * @throws IOException
3022 * if an I/O error occurs opening or creating the file
3023 * @throws UnsupportedOperationException
3024 * if an unsupported option is specified
3025 * @throws SecurityException
3026 * In the case of the default provider, and a security manager is
3027 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3028 * method is invoked to check write access to the file. The {@link
3029 * SecurityManager#checkDelete(String) checkDelete} method is
3030 * invoked to check delete access if the file is opened with the
3031 * {@code DELETE_ON_CLOSE} option.
3032 *
3033 * @since 1.8
3034 */
3035 public static BufferedWriter newBufferedWriter(Path path, OpenOption... options)
3036 throws IOException
3037 {
3038 return newBufferedWriter(path, StandardCharsets.UTF_8, options);
3039 }
3040
3041 /**
3042 * Copies all bytes from an input stream to a file. On return, the input
3043 * stream will be at end of stream.
3044 *
3045 * <p> By default, the copy fails if the target file already exists or is a
3046 * symbolic link. If the {@link StandardCopyOption#REPLACE_EXISTING
3047 * REPLACE_EXISTING} option is specified, and the target file already exists,
3048 * then it is replaced if it is not a non-empty directory. If the target
3049 * file exists and is a symbolic link, then the symbolic link is replaced.
3050 * In this release, the {@code REPLACE_EXISTING} option is the only option
3051 * required to be supported by this method. Additional options may be
3052 * supported in future releases.
3053 *
3054 * <p> If an I/O error occurs reading from the input stream or writing to
3055 * the file, then it may do so after the target file has been created and
3056 * after some bytes have been read or written. Consequently the input
3057 * stream may not be at end of stream and may be in an inconsistent state.
3058 * It is strongly recommended that the input stream be promptly closed if an
3059 * I/O error occurs.
3060 *
3061 * <p> This method may block indefinitely reading from the input stream (or
3062 * writing to the file). The behavior for the case that the input stream is
3063 * <i>asynchronously closed</i> or the thread interrupted during the copy is
3064 * highly input stream and file system provider specific and therefore not
3065 * specified.
3066 *
3067 * <p> <b>Usage example</b>: Suppose we want to capture a web page and save
3068 * it to a file:
3069 * <pre>
3070 * Path path = ...
3071 * URI u = URI.create("http://www.example.com/");
3072 * try (InputStream in = u.toURL().openStream()) {
3073 * Files.copy(in, path);
3074 * }
3075 * </pre>
3076 *
3077 * @param in
3078 * the input stream to read from
3079 * @param target
3080 * the path to the file
3081 * @param options
3082 * options specifying how the copy should be done
3083 *
3084 * @return the number of bytes read or written
3085 *
3086 * @throws IOException
3087 * if an I/O error occurs when reading or writing
3088 * @throws FileAlreadyExistsException
3089 * if the target file exists but cannot be replaced because the
3090 * {@code REPLACE_EXISTING} option is not specified <i>(optional
3091 * specific exception)</i>
3092 * @throws DirectoryNotEmptyException
3093 * the {@code REPLACE_EXISTING} option is specified but the file
3094 * cannot be replaced because it is a non-empty directory
3095 * <i>(optional specific exception)</i> *
3096 * @throws UnsupportedOperationException
3097 * if {@code options} contains a copy option that is not supported
3098 * @throws SecurityException
3099 * In the case of the default provider, and a security manager is
3100 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3101 * method is invoked to check write access to the file. Where the
3102 * {@code REPLACE_EXISTING} option is specified, the security
3103 * manager's {@link SecurityManager#checkDelete(String) checkDelete}
3104 * method is invoked to check that an existing file can be deleted.
3105 */
3106 public static long copy(InputStream in, Path target, CopyOption... options)
3107 throws IOException
3108 {
3109 // ensure not null before opening file
3110 Objects.requireNonNull(in);
3111
3112 // check for REPLACE_EXISTING
3113 boolean replaceExisting = false;
3114 for (CopyOption opt: options) {
3115 if (opt == StandardCopyOption.REPLACE_EXISTING) {
3116 replaceExisting = true;
3117 } else {
3118 if (opt == null) {
3119 throw new NullPointerException("options contains 'null'");
3120 } else {
3121 throw new UnsupportedOperationException(opt + " not supported");
3122 }
3123 }
3124 }
3125
3126 // attempt to delete an existing file
3127 SecurityException se = null;
3128 if (replaceExisting) {
3129 try {
3130 deleteIfExists(target);
3131 } catch (SecurityException x) {
3132 se = x;
3133 }
3134 }
3135
3136 // attempt to create target file. If it fails with
3137 // FileAlreadyExistsException then it may be because the security
3138 // manager prevented us from deleting the file, in which case we just
3139 // throw the SecurityException.
3140 OutputStream ostream;
3141 try {
3142 ostream = newOutputStream(target, StandardOpenOption.CREATE_NEW,
3143 StandardOpenOption.WRITE);
3144 } catch (FileAlreadyExistsException x) {
3145 if (se != null)
3146 throw se;
3147 // someone else won the race and created the file
3148 throw x;
3149 }
3150
3151 // do the copy
3152 try (OutputStream out = ostream) {
3153 return in.transferTo(out);
3154 }
3155 }
3156
3157 /**
3158 * Copies all bytes from a file to an output stream.
3159 *
3160 * <p> If an I/O error occurs reading from the file or writing to the output
3161 * stream, then it may do so after some bytes have been read or written.
3162 * Consequently the output stream may be in an inconsistent state. It is
3163 * strongly recommended that the output stream be promptly closed if an I/O
3164 * error occurs.
3165 *
3166 * <p> This method may block indefinitely writing to the output stream (or
3167 * reading from the file). The behavior for the case that the output stream
3168 * is <i>asynchronously closed</i> or the thread interrupted during the copy
3169 * is highly output stream and file system provider specific and therefore
3170 * not specified.
3171 *
3172 * <p> Note that if the given output stream is {@link java.io.Flushable}
3173 * then its {@link java.io.Flushable#flush flush} method may need to invoked
3174 * after this method completes so as to flush any buffered output.
3175 *
3176 * @param source
3177 * the path to the file
3178 * @param out
3179 * the output stream to write to
3180 *
3181 * @return the number of bytes read or written
3182 *
3183 * @throws IOException
3184 * if an I/O error occurs when reading or writing
3185 * @throws SecurityException
3186 * In the case of the default provider, and a security manager is
3187 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3188 * method is invoked to check read access to the file.
3189 */
3190 public static long copy(Path source, OutputStream out) throws IOException {
3191 // ensure not null before opening file
3192 Objects.requireNonNull(out);
3193
3194 try (InputStream in = newInputStream(source)) {
3195 return in.transferTo(out);
3196 }
3197 }
3198
3199 /**
3200 * The maximum size of array to allocate.
3201 * Some VMs reserve some header words in an array.
3202 * Attempts to allocate larger arrays may result in
3203 * OutOfMemoryError: Requested array size exceeds VM limit
3204 */
3205 private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
3206
3207 private static final jdk.internal.access.JavaLangAccess JLA =
3208 jdk.internal.access.SharedSecrets.getJavaLangAccess();
3209
3210 /**
3211 * Reads all the bytes from an input stream. Uses {@code initialSize} as a hint
3212 * about how many bytes the stream will have.
3213 *
3214 * @param source
3215 * the input stream to read from
3216 * @param initialSize
3217 * the initial size of the byte array to allocate
3218 *
3219 * @return a byte array containing the bytes read from the file
3220 *
3221 * @throws IOException
3222 * if an I/O error occurs reading from the stream
3223 * @throws OutOfMemoryError
3224 * if an array of the required size cannot be allocated
3225 */
3226 private static byte[] read(InputStream source, int initialSize) throws IOException {
3227 int capacity = initialSize;
3228 byte[] buf = new byte[capacity];
3229 int nread = 0;
3230 int n;
3231 for (;;) {
3232 // read to EOF which may read more or less than initialSize (eg: file
3233 // is truncated while we are reading)
3234 while ((n = source.read(buf, nread, capacity - nread)) > 0)
3235 nread += n;
3236
3237 // if last call to source.read() returned -1, we are done
3238 // otherwise, try to read one more byte; if that failed we're done too
3239 if (n < 0 || (n = source.read()) < 0)
3240 break;
3241
3242 // one more byte was read; need to allocate a larger buffer
3243 if (capacity <= MAX_BUFFER_SIZE - capacity) {
3244 capacity = Math.max(capacity << 1, BUFFER_SIZE);
3245 } else {
3246 if (capacity == MAX_BUFFER_SIZE)
3247 throw new OutOfMemoryError("Required array size too large");
3248 capacity = MAX_BUFFER_SIZE;
3249 }
3250 buf = Arrays.copyOf(buf, capacity);
3251 buf[nread++] = (byte)n;
3252 }
3253 return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
3254 }
3255
3256 /**
3257 * Reads all the bytes from a file. The method ensures that the file is
3258 * closed when all bytes have been read or an I/O error, or other runtime
3259 * exception, is thrown.
3260 *
3261 * <p> Note that this method is intended for simple cases where it is
3262 * convenient to read all bytes into a byte array. It is not intended for
3263 * reading in large files.
3264 *
3265 * @param path
3266 * the path to the file
3267 *
3268 * @return a byte array containing the bytes read from the file
3269 *
3270 * @throws IOException
3271 * if an I/O error occurs reading from the stream
3272 * @throws OutOfMemoryError
3273 * if an array of the required size cannot be allocated, for
3274 * example the file is larger that {@code 2GB}
3275 * @throws SecurityException
3276 * In the case of the default provider, and a security manager is
3277 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3278 * method is invoked to check read access to the file.
3279 */
3280 public static byte[] readAllBytes(Path path) throws IOException {
3281 try (SeekableByteChannel sbc = Files.newByteChannel(path);
3282 InputStream in = Channels.newInputStream(sbc)) {
3283 if (sbc instanceof FileChannelImpl)
3284 ((FileChannelImpl) sbc).setUninterruptible();
3285 long size = sbc.size();
3286 if (size > (long) MAX_BUFFER_SIZE)
3287 throw new OutOfMemoryError("Required array size too large");
3288 return read(in, (int)size);
3289 }
3290 }
3291
3292 /**
3293 * Reads all content from a file into a string, decoding from bytes to characters
3294 * using the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
3295 * The method ensures that the file is closed when all content have been read
3296 * or an I/O error, or other runtime exception, is thrown.
3297 *
3298 * <p> This method is equivalent to:
3299 * {@code readString(path, StandardCharsets.UTF_8) }
3300 *
3301 * @param path the path to the file
3302 *
3303 * @return a String containing the content read from the file
3304 *
3305 * @throws IOException
3306 * if an I/O error occurs reading from the file or a malformed or
3307 * unmappable byte sequence is read
3308 * @throws OutOfMemoryError
3309 * if the file is extremely large, for example larger than {@code 2GB}
3310 * @throws SecurityException
3311 * In the case of the default provider, and a security manager is
3312 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3313 * method is invoked to check read access to the file.
3314 *
3315 * @since 11
3316 */
3317 public static String readString(Path path) throws IOException {
3318 return readString(path, StandardCharsets.UTF_8);
3319 }
3320
3321 /**
3322 * Reads all characters from a file into a string, decoding from bytes to characters
3323 * using the specified {@linkplain Charset charset}.
3324 * The method ensures that the file is closed when all content have been read
3325 * or an I/O error, or other runtime exception, is thrown.
3326 *
3327 * <p> This method reads all content including the line separators in the middle
3328 * and/or at the end. The resulting string will contain line separators as they
3329 * appear in the file.
3330 *
3331 * @apiNote
3332 * This method is intended for simple cases where it is appropriate and convenient
3333 * to read the content of a file into a String. It is not intended for reading
3334 * very large files.
3335 *
3336 *
3337 *
3338 * @param path the path to the file
3339 * @param cs the charset to use for decoding
3340 *
3341 * @return a String containing the content read from the file
3342 *
3343 * @throws IOException
3344 * if an I/O error occurs reading from the file or a malformed or
3345 * unmappable byte sequence is read
3346 * @throws OutOfMemoryError
3347 * if the file is extremely large, for example larger than {@code 2GB}
3348 * @throws SecurityException
3349 * In the case of the default provider, and a security manager is
3350 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3351 * method is invoked to check read access to the file.
3352 *
3353 * @since 11
3354 */
3355 public static String readString(Path path, Charset cs) throws IOException {
3356 Objects.requireNonNull(path);
3357 Objects.requireNonNull(cs);
3358
3359 byte[] ba = readAllBytes(path);
3360 return JLA.newStringNoRepl(ba, cs);
3361 }
3362
3363 /**
3364 * Read all lines from a file. This method ensures that the file is
3365 * closed when all bytes have been read or an I/O error, or other runtime
3366 * exception, is thrown. Bytes from the file are decoded into characters
3367 * using the specified charset.
3368 *
3369 * <p> This method recognizes the following as line terminators:
3370 * <ul>
3371 * <li> <code>\u000D</code> followed by <code>\u000A</code>,
3372 * CARRIAGE RETURN followed by LINE FEED </li>
3373 * <li> <code>\u000A</code>, LINE FEED </li>
3374 * <li> <code>\u000D</code>, CARRIAGE RETURN </li>
3375 * </ul>
3376 * <p> Additional Unicode line terminators may be recognized in future
3377 * releases.
3378 *
3379 * <p> Note that this method is intended for simple cases where it is
3380 * convenient to read all lines in a single operation. It is not intended
3381 * for reading in large files.
3382 *
3383 * @param path
3384 * the path to the file
3385 * @param cs
3386 * the charset to use for decoding
3387 *
3388 * @return the lines from the file as a {@code List}; whether the {@code
3389 * List} is modifiable or not is implementation dependent and
3390 * therefore not specified
3391 *
3392 * @throws IOException
3393 * if an I/O error occurs reading from the file or a malformed or
3394 * unmappable byte sequence is read
3395 * @throws SecurityException
3396 * In the case of the default provider, and a security manager is
3397 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3398 * method is invoked to check read access to the file.
3399 *
3400 * @see #newBufferedReader
3401 */
3402 public static List<String> readAllLines(Path path, Charset cs) throws IOException {
3403 try (BufferedReader reader = newBufferedReader(path, cs)) {
3404 List<String> result = new ArrayList<>();
3405 for (;;) {
3406 String line = reader.readLine();
3407 if (line == null)
3408 break;
3409 result.add(line);
3410 }
3411 return result;
3412 }
3413 }
3414
3415 /**
3416 * Read all lines from a file. Bytes from the file are decoded into characters
3417 * using the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
3418 *
3419 * <p> This method works as if invoking it were equivalent to evaluating the
3420 * expression:
3421 * <pre>{@code
3422 * Files.readAllLines(path, StandardCharsets.UTF_8)
3423 * }</pre>
3424 *
3425 * @param path
3426 * the path to the file
3427 *
3428 * @return the lines from the file as a {@code List}; whether the {@code
3429 * List} is modifiable or not is implementation dependent and
3430 * therefore not specified
3431 *
3432 * @throws IOException
3433 * if an I/O error occurs reading from the file or a malformed or
3434 * unmappable byte sequence is read
3435 * @throws SecurityException
3436 * In the case of the default provider, and a security manager is
3437 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3438 * method is invoked to check read access to the file.
3439 *
3440 * @since 1.8
3441 */
3442 public static List<String> readAllLines(Path path) throws IOException {
3443 return readAllLines(path, StandardCharsets.UTF_8);
3444 }
3445
3446 /**
3447 * Writes bytes to a file. The {@code options} parameter specifies how
3448 * the file is created or opened. If no options are present then this method
3449 * works as if the {@link StandardOpenOption#CREATE CREATE}, {@link
3450 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3451 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3452 * opens the file for writing, creating the file if it doesn't exist, or
3453 * initially truncating an existing {@link #isRegularFile regular-file} to
3454 * a size of {@code 0}. All bytes in the byte array are written to the file.
3455 * The method ensures that the file is closed when all bytes have been
3456 * written (or an I/O error or other runtime exception is thrown). If an I/O
3457 * error occurs then it may do so after the file has been created or
3458 * truncated, or after some bytes have been written to the file.
3459 *
3460 * <p> <b>Usage example</b>: By default the method creates a new file or
3461 * overwrites an existing file. Suppose you instead want to append bytes
3462 * to an existing file:
3463 * <pre>
3464 * Path path = ...
3465 * byte[] bytes = ...
3466 * Files.write(path, bytes, StandardOpenOption.APPEND);
3467 * </pre>
3468 *
3469 * @param path
3470 * the path to the file
3471 * @param bytes
3472 * the byte array with the bytes to write
3473 * @param options
3474 * options specifying how the file is opened
3475 *
3476 * @return the path
3477 *
3478 * @throws IllegalArgumentException
3479 * if {@code options} contains an invalid combination of options
3480 * @throws IOException
3481 * if an I/O error occurs writing to or creating the file
3482 * @throws UnsupportedOperationException
3483 * if an unsupported option is specified
3484 * @throws SecurityException
3485 * In the case of the default provider, and a security manager is
3486 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3487 * method is invoked to check write access to the file. The {@link
3488 * SecurityManager#checkDelete(String) checkDelete} method is
3489 * invoked to check delete access if the file is opened with the
3490 * {@code DELETE_ON_CLOSE} option.
3491 */
3492 public static Path write(Path path, byte[] bytes, OpenOption... options)
3493 throws IOException
3494 {
3495 // ensure bytes is not null before opening file
3496 Objects.requireNonNull(bytes);
3497
3498 try (OutputStream out = Files.newOutputStream(path, options)) {
3499 int len = bytes.length;
3500 int rem = len;
3501 while (rem > 0) {
3502 int n = Math.min(rem, BUFFER_SIZE);
3503 out.write(bytes, (len-rem), n);
3504 rem -= n;
3505 }
3506 }
3507 return path;
3508 }
3509
3510 /**
3511 * Write lines of text to a file. Each line is a char sequence and is
3512 * written to the file in sequence with each line terminated by the
3513 * platform's line separator, as defined by the system property {@code
3514 * line.separator}. Characters are encoded into bytes using the specified
3515 * charset.
3516 *
3517 * <p> The {@code options} parameter specifies how the file is created
3518 * or opened. If no options are present then this method works as if the
3519 * {@link StandardOpenOption#CREATE CREATE}, {@link
3520 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3521 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3522 * opens the file for writing, creating the file if it doesn't exist, or
3523 * initially truncating an existing {@link #isRegularFile regular-file} to
3524 * a size of {@code 0}. The method ensures that the file is closed when all
3525 * lines have been written (or an I/O error or other runtime exception is
3526 * thrown). If an I/O error occurs then it may do so after the file has
3527 * been created or truncated, or after some bytes have been written to the
3528 * file.
3529 *
3530 * @param path
3531 * the path to the file
3532 * @param lines
3533 * an object to iterate over the char sequences
3534 * @param cs
3535 * the charset to use for encoding
3536 * @param options
3537 * options specifying how the file is opened
3538 *
3539 * @return the path
3540 *
3541 * @throws IllegalArgumentException
3542 * if {@code options} contains an invalid combination of options
3543 * @throws IOException
3544 * if an I/O error occurs writing to or creating the file, or the
3545 * text cannot be encoded using the specified charset
3546 * @throws UnsupportedOperationException
3547 * if an unsupported option is specified
3548 * @throws SecurityException
3549 * In the case of the default provider, and a security manager is
3550 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3551 * method is invoked to check write access to the file. The {@link
3552 * SecurityManager#checkDelete(String) checkDelete} method is
3553 * invoked to check delete access if the file is opened with the
3554 * {@code DELETE_ON_CLOSE} option.
3555 */
3556 public static Path write(Path path, Iterable<? extends CharSequence> lines,
3557 Charset cs, OpenOption... options)
3558 throws IOException
3559 {
3560 // ensure lines is not null before opening file
3561 Objects.requireNonNull(lines);
3562 CharsetEncoder encoder = cs.newEncoder();
3563 OutputStream out = newOutputStream(path, options);
3564 try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, encoder))) {
3565 for (CharSequence line: lines) {
3566 writer.append(line);
3567 writer.newLine();
3568 }
3569 }
3570 return path;
3571 }
3572
3573 /**
3574 * Write lines of text to a file. Characters are encoded into bytes using
3575 * the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
3576 *
3577 * <p> This method works as if invoking it were equivalent to evaluating the
3578 * expression:
3579 * <pre>{@code
3580 * Files.write(path, lines, StandardCharsets.UTF_8, options);
3581 * }</pre>
3582 *
3583 * @param path
3584 * the path to the file
3585 * @param lines
3586 * an object to iterate over the char sequences
3587 * @param options
3588 * options specifying how the file is opened
3589 *
3590 * @return the path
3591 *
3592 * @throws IllegalArgumentException
3593 * if {@code options} contains an invalid combination of options
3594 * @throws IOException
3595 * if an I/O error occurs writing to or creating the file, or the
3596 * text cannot be encoded as {@code UTF-8}
3597 * @throws UnsupportedOperationException
3598 * if an unsupported option is specified
3599 * @throws SecurityException
3600 * In the case of the default provider, and a security manager is
3601 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3602 * method is invoked to check write access to the file. The {@link
3603 * SecurityManager#checkDelete(String) checkDelete} method is
3604 * invoked to check delete access if the file is opened with the
3605 * {@code DELETE_ON_CLOSE} option.
3606 *
3607 * @since 1.8
3608 */
3609 public static Path write(Path path,
3610 Iterable<? extends CharSequence> lines,
3611 OpenOption... options)
3612 throws IOException
3613 {
3614 return write(path, lines, StandardCharsets.UTF_8, options);
3615 }
3616
3617 /**
3618 * Write a {@linkplain java.lang.CharSequence CharSequence} to a file.
3619 * Characters are encoded into bytes using the
3620 * {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
3621 *
3622 * <p> This method is equivalent to:
3623 * {@code writeString(path, test, StandardCharsets.UTF_8, options) }
3624 *
3625 * @param path
3626 * the path to the file
3627 * @param csq
3628 * the CharSequence to be written
3629 * @param options
3630 * options specifying how the file is opened
3631 *
3632 * @return the path
3633 *
3634 * @throws IllegalArgumentException
3635 * if {@code options} contains an invalid combination of options
3636 * @throws IOException
3637 * if an I/O error occurs writing to or creating the file, or the
3638 * text cannot be encoded using the specified charset
3639 * @throws UnsupportedOperationException
3640 * if an unsupported option is specified
3641 * @throws SecurityException
3642 * In the case of the default provider, and a security manager is
3643 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3644 * method is invoked to check write access to the file. The {@link
3645 * SecurityManager#checkDelete(String) checkDelete} method is
3646 * invoked to check delete access if the file is opened with the
3647 * {@code DELETE_ON_CLOSE} option.
3648 *
3649 * @since 11
3650 */
3651 public static Path writeString(Path path, CharSequence csq, OpenOption... options)
3652 throws IOException
3653 {
3654 return writeString(path, csq, StandardCharsets.UTF_8, options);
3655 }
3656
3657 /**
3658 * Write a {@linkplain java.lang.CharSequence CharSequence} to a file.
3659 * Characters are encoded into bytes using the specified
3660 * {@linkplain java.nio.charset.Charset charset}.
3661 *
3662 * <p> All characters are written as they are, including the line separators in
3663 * the char sequence. No extra characters are added.
3664 *
3665 * <p> The {@code options} parameter specifies how the file is created
3666 * or opened. If no options are present then this method works as if the
3667 * {@link StandardOpenOption#CREATE CREATE}, {@link
3668 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3669 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3670 * opens the file for writing, creating the file if it doesn't exist, or
3671 * initially truncating an existing {@link #isRegularFile regular-file} to
3672 * a size of {@code 0}.
3673 *
3674 *
3675 * @param path
3676 * the path to the file
3677 * @param csq
3678 * the CharSequence to be written
3679 * @param cs
3680 * the charset to use for encoding
3681 * @param options
3682 * options specifying how the file is opened
3683 *
3684 * @return the path
3685 *
3686 * @throws IllegalArgumentException
3687 * if {@code options} contains an invalid combination of options
3688 * @throws IOException
3689 * if an I/O error occurs writing to or creating the file, or the
3690 * text cannot be encoded using the specified charset
3691 * @throws UnsupportedOperationException
3692 * if an unsupported option is specified
3693 * @throws SecurityException
3694 * In the case of the default provider, and a security manager is
3695 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3696 * method is invoked to check write access to the file. The {@link
3697 * SecurityManager#checkDelete(String) checkDelete} method is
3698 * invoked to check delete access if the file is opened with the
3699 * {@code DELETE_ON_CLOSE} option.
3700 *
3701 * @since 11
3702 */
3703 public static Path writeString(Path path, CharSequence csq, Charset cs, OpenOption... options)
3704 throws IOException
3705 {
3706 // ensure the text is not null before opening file
3707 Objects.requireNonNull(path);
3708 Objects.requireNonNull(csq);
3709 Objects.requireNonNull(cs);
3710
3711 byte[] bytes = JLA.getBytesNoRepl(String.valueOf(csq), cs);
3712 write(path, bytes, options);
3713
3714 return path;
3715 }
3716
3717 // -- Stream APIs --
3718
3719 /**
3720 * Return a lazily populated {@code Stream}, the elements of
3721 * which are the entries in the directory. The listing is not recursive.
3722 *
3723 * <p> The elements of the stream are {@link Path} objects that are
3724 * obtained as if by {@link Path#resolve(Path) resolving} the name of the
3725 * directory entry against {@code dir}. Some file systems maintain special
3726 * links to the directory itself and the directory's parent directory.
3727 * Entries representing these links are not included.
3728 *
3729 * <p> The stream is <i>weakly consistent</i>. It is thread safe but does
3730 * not freeze the directory while iterating, so it may (or may not)
3731 * reflect updates to the directory that occur after returning from this
3732 * method.
3733 *
3734 * <p> The returned stream contains a reference to an open directory.
3735 * The directory is closed by closing the stream.
3736 *
3737 * <p> Operating on a closed stream behaves as if the end of stream
3738 * has been reached. Due to read-ahead, one or more elements may be
3739 * returned after the stream has been closed.
3740 *
3741 * <p> If an {@link IOException} is thrown when accessing the directory
3742 * after this method has returned, it is wrapped in an {@link
3743 * UncheckedIOException} which will be thrown from the method that caused
3744 * the access to take place.
3745 *
3746 * @apiNote
3747 * This method must be used within a try-with-resources statement or similar
3748 * control structure to ensure that the stream's open directory is closed
3749 * promptly after the stream's operations have completed.
3750 *
3751 * @param dir The path to the directory
3752 *
3753 * @return The {@code Stream} describing the content of the
3754 * directory
3755 *
3756 * @throws NotDirectoryException
3757 * if the file could not otherwise be opened because it is not
3758 * a directory <i>(optional specific exception)</i>
3759 * @throws IOException
3760 * if an I/O error occurs when opening the directory
3761 * @throws SecurityException
3762 * In the case of the default provider, and a security manager is
3763 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3764 * method is invoked to check read access to the directory.
3765 *
3766 * @see #newDirectoryStream(Path)
3767 * @since 1.8
3768 */
3769 public static Stream<Path> list(Path dir) throws IOException {
3770 DirectoryStream<Path> ds = Files.newDirectoryStream(dir);
3771 try {
3772 final Iterator<Path> delegate = ds.iterator();
3773
3774 // Re-wrap DirectoryIteratorException to UncheckedIOException
3775 Iterator<Path> iterator = new Iterator<>() {
3776 @Override
3777 public boolean hasNext() {
3778 try {
3779 return delegate.hasNext();
3780 } catch (DirectoryIteratorException e) {
3781 throw new UncheckedIOException(e.getCause());
3782 }
3783 }
3784 @Override
3785 public Path next() {
3786 try {
3787 return delegate.next();
3788 } catch (DirectoryIteratorException e) {
3789 throw new UncheckedIOException(e.getCause());
3790 }
3791 }
3792 };
3793
3794 Spliterator<Path> spliterator =
3795 Spliterators.spliteratorUnknownSize(iterator, Spliterator.DISTINCT);
3796 return StreamSupport.stream(spliterator, false)
3797 .onClose(asUncheckedRunnable(ds));
3798 } catch (Error|RuntimeException e) {
3799 try {
3800 ds.close();
3801 } catch (IOException ex) {
3802 try {
3803 e.addSuppressed(ex);
3804 } catch (Throwable ignore) {}
3805 }
3806 throw e;
3807 }
3808 }
3809
3810 /**
3811 * Return a {@code Stream} that is lazily populated with {@code
3812 * Path} by walking the file tree rooted at a given starting file. The
3813 * file tree is traversed <em>depth-first</em>, the elements in the stream
3814 * are {@link Path} objects that are obtained as if by {@link
3815 * Path#resolve(Path) resolving} the relative path against {@code start}.
3816 *
3817 * <p> The {@code stream} walks the file tree as elements are consumed.
3818 * The {@code Stream} returned is guaranteed to have at least one
3819 * element, the starting file itself. For each file visited, the stream
3820 * attempts to read its {@link BasicFileAttributes}. If the file is a
3821 * directory and can be opened successfully, entries in the directory, and
3822 * their <em>descendants</em> will follow the directory in the stream as
3823 * they are encountered. When all entries have been visited, then the
3824 * directory is closed. The file tree walk then continues at the next
3825 * <em>sibling</em> of the directory.
3826 *
3827 * <p> The stream is <i>weakly consistent</i>. It does not freeze the
3828 * file tree while iterating, so it may (or may not) reflect updates to
3829 * the file tree that occur after returned from this method.
3830 *
3831 * <p> By default, symbolic links are not automatically followed by this
3832 * method. If the {@code options} parameter contains the {@link
3833 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then symbolic links are
3834 * followed. When following links, and the attributes of the target cannot
3835 * be read, then this method attempts to get the {@code BasicFileAttributes}
3836 * of the link.
3837 *
3838 * <p> If the {@code options} parameter contains the {@link
3839 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then the stream keeps
3840 * track of directories visited so that cycles can be detected. A cycle
3841 * arises when there is an entry in a directory that is an ancestor of the
3842 * directory. Cycle detection is done by recording the {@link
3843 * java.nio.file.attribute.BasicFileAttributes#fileKey file-key} of directories,
3844 * or if file keys are not available, by invoking the {@link #isSameFile
3845 * isSameFile} method to test if a directory is the same file as an
3846 * ancestor. When a cycle is detected it is treated as an I/O error with
3847 * an instance of {@link FileSystemLoopException}.
3848 *
3849 * <p> The {@code maxDepth} parameter is the maximum number of levels of
3850 * directories to visit. A value of {@code 0} means that only the starting
3851 * file is visited, unless denied by the security manager. A value of
3852 * {@link Integer#MAX_VALUE MAX_VALUE} may be used to indicate that all
3853 * levels should be visited.
3854 *
3855 * <p> When a security manager is installed and it denies access to a file
3856 * (or directory), then it is ignored and not included in the stream.
3857 *
3858 * <p> The returned stream contains references to one or more open directories.
3859 * The directories are closed by closing the stream.
3860 *
3861 * <p> If an {@link IOException} is thrown when accessing the directory
3862 * after this method has returned, it is wrapped in an {@link
3863 * UncheckedIOException} which will be thrown from the method that caused
3864 * the access to take place.
3865 *
3866 * @apiNote
3867 * This method must be used within a try-with-resources statement or similar
3868 * control structure to ensure that the stream's open directories are closed
3869 * promptly after the stream's operations have completed.
3870 *
3871 * @param start
3872 * the starting file
3873 * @param maxDepth
3874 * the maximum number of directory levels to visit
3875 * @param options
3876 * options to configure the traversal
3877 *
3878 * @return the {@link Stream} of {@link Path}
3879 *
3880 * @throws IllegalArgumentException
3881 * if the {@code maxDepth} parameter is negative
3882 * @throws SecurityException
3883 * If the security manager denies access to the starting file.
3884 * In the case of the default provider, the {@link
3885 * SecurityManager#checkRead(String) checkRead} method is invoked
3886 * to check read access to the directory.
3887 * @throws IOException
3888 * if an I/O error is thrown when accessing the starting file.
3889 * @since 1.8
3890 */
3891 public static Stream<Path> walk(Path start,
3892 int maxDepth,
3893 FileVisitOption... options)
3894 throws IOException
3895 {
3896 FileTreeIterator iterator = new FileTreeIterator(start, maxDepth, options);
3897 try {
3898 Spliterator<FileTreeWalker.Event> spliterator =
3899 Spliterators.spliteratorUnknownSize(iterator, Spliterator.DISTINCT);
3900 return StreamSupport.stream(spliterator, false)
3901 .onClose(iterator::close)
3902 .map(entry -> entry.file());
3903 } catch (Error|RuntimeException e) {
3904 iterator.close();
3905 throw e;
3906 }
3907 }
3908
3909 /**
3910 * Return a {@code Stream} that is lazily populated with {@code
3911 * Path} by walking the file tree rooted at a given starting file. The
3912 * file tree is traversed <em>depth-first</em>, the elements in the stream
3913 * are {@link Path} objects that are obtained as if by {@link
3914 * Path#resolve(Path) resolving} the relative path against {@code start}.
3915 *
3916 * <p> This method works as if invoking it were equivalent to evaluating the
3917 * expression:
3918 * <blockquote><pre>
3919 * walk(start, Integer.MAX_VALUE, options)
3920 * </pre></blockquote>
3921 * In other words, it visits all levels of the file tree.
3922 *
3923 * <p> The returned stream contains references to one or more open directories.
3924 * The directories are closed by closing the stream.
3925 *
3926 * @apiNote
3927 * This method must be used within a try-with-resources statement or similar
3928 * control structure to ensure that the stream's open directories are closed
3929 * promptly after the stream's operations have completed.
3930 *
3931 * @param start
3932 * the starting file
3933 * @param options
3934 * options to configure the traversal
3935 *
3936 * @return the {@link Stream} of {@link Path}
3937 *
3938 * @throws SecurityException
3939 * If the security manager denies access to the starting file.
3940 * In the case of the default provider, the {@link
3941 * SecurityManager#checkRead(String) checkRead} method is invoked
3942 * to check read access to the directory.
3943 * @throws IOException
3944 * if an I/O error is thrown when accessing the starting file.
3945 *
3946 * @see #walk(Path, int, FileVisitOption...)
3947 * @since 1.8
3948 */
3949 public static Stream<Path> walk(Path start, FileVisitOption... options) throws IOException {
3950 return walk(start, Integer.MAX_VALUE, options);
3951 }
3952
3953 /**
3954 * Return a {@code Stream} that is lazily populated with {@code
3955 * Path} by searching for files in a file tree rooted at a given starting
3956 * file.
3957 *
3958 * <p> This method walks the file tree in exactly the manner specified by
3959 * the {@link #walk walk} method. For each file encountered, the given
3960 * {@link BiPredicate} is invoked with its {@link Path} and {@link
3961 * BasicFileAttributes}. The {@code Path} object is obtained as if by
3962 * {@link Path#resolve(Path) resolving} the relative path against {@code
3963 * start} and is only included in the returned {@link Stream} if
3964 * the {@code BiPredicate} returns true. Compare to calling {@link
3965 * java.util.stream.Stream#filter filter} on the {@code Stream}
3966 * returned by {@code walk} method, this method may be more efficient by
3967 * avoiding redundant retrieval of the {@code BasicFileAttributes}.
3968 *
3969 * <p> The returned stream contains references to one or more open directories.
3970 * The directories are closed by closing the stream.
3971 *
3972 * <p> If an {@link IOException} is thrown when accessing the directory
3973 * after returned from this method, it is wrapped in an {@link
3974 * UncheckedIOException} which will be thrown from the method that caused
3975 * the access to take place.
3976 *
3977 * @apiNote
3978 * This method must be used within a try-with-resources statement or similar
3979 * control structure to ensure that the stream's open directories are closed
3980 * promptly after the stream's operations have completed.
3981 *
3982 * @param start
3983 * the starting file
3984 * @param maxDepth
3985 * the maximum number of directory levels to search
3986 * @param matcher
3987 * the function used to decide whether a file should be included
3988 * in the returned stream
3989 * @param options
3990 * options to configure the traversal
3991 *
3992 * @return the {@link Stream} of {@link Path}
3993 *
3994 * @throws IllegalArgumentException
3995 * if the {@code maxDepth} parameter is negative
3996 * @throws SecurityException
3997 * If the security manager denies access to the starting file.
3998 * In the case of the default provider, the {@link
3999 * SecurityManager#checkRead(String) checkRead} method is invoked
4000 * to check read access to the directory.
4001 * @throws IOException
4002 * if an I/O error is thrown when accessing the starting file.
4003 *
4004 * @see #walk(Path, int, FileVisitOption...)
4005 * @since 1.8
4006 */
4007 public static Stream<Path> find(Path start,
4008 int maxDepth,
4009 BiPredicate<Path, BasicFileAttributes> matcher,
4010 FileVisitOption... options)
4011 throws IOException
4012 {
4013 FileTreeIterator iterator = new FileTreeIterator(start, maxDepth, options);
4014 try {
4015 Spliterator<FileTreeWalker.Event> spliterator =
4016 Spliterators.spliteratorUnknownSize(iterator, Spliterator.DISTINCT);
4017 return StreamSupport.stream(spliterator, false)
4018 .onClose(iterator::close)
4019 .filter(entry -> matcher.test(entry.file(), entry.attributes()))
4020 .map(entry -> entry.file());
4021 } catch (Error|RuntimeException e) {
4022 iterator.close();
4023 throw e;
4024 }
4025 }
4026
4027
4028 /**
4029 * Read all lines from a file as a {@code Stream}. Unlike {@link
4030 * #readAllLines(Path, Charset) readAllLines}, this method does not read
4031 * all lines into a {@code List}, but instead populates lazily as the stream
4032 * is consumed.
4033 *
4034 * <p> Bytes from the file are decoded into characters using the specified
4035 * charset and the same line terminators as specified by {@code
4036 * readAllLines} are supported.
4037 *
4038 * <p> The returned stream contains a reference to an open file. The file
4039 * is closed by closing the stream.
4040 *
4041 * <p> The file contents should not be modified during the execution of the
4042 * terminal stream operation. Otherwise, the result of the terminal stream
4043 * operation is undefined.
4044 *
4045 * <p> After this method returns, then any subsequent I/O exception that
4046 * occurs while reading from the file or when a malformed or unmappable byte
4047 * sequence is read, is wrapped in an {@link UncheckedIOException} that will
4048 * be thrown from the
4049 * {@link java.util.stream.Stream} method that caused the read to take
4050 * place. In case an {@code IOException} is thrown when closing the file,
4051 * it is also wrapped as an {@code UncheckedIOException}.
4052 *
4053 * @apiNote
4054 * This method must be used within a try-with-resources statement or similar
4055 * control structure to ensure that the stream's open file is closed promptly
4056 * after the stream's operations have completed.
4057 *
4058 * @implNote
4059 * This implementation supports good parallel stream performance for the
4060 * standard charsets {@link StandardCharsets#UTF_8 UTF-8},
4061 * {@link StandardCharsets#US_ASCII US-ASCII} and
4062 * {@link StandardCharsets#ISO_8859_1 ISO-8859-1}. Such
4063 * <em>line-optimal</em> charsets have the property that the encoded bytes
4064 * of a line feed ('\n') or a carriage return ('\r') are efficiently
4065 * identifiable from other encoded characters when randomly accessing the
4066 * bytes of the file.
4067 *
4068 * <p> For non-<em>line-optimal</em> charsets the stream source's
4069 * spliterator has poor splitting properties, similar to that of a
4070 * spliterator associated with an iterator or that associated with a stream
4071 * returned from {@link BufferedReader#lines()}. Poor splitting properties
4072 * can result in poor parallel stream performance.
4073 *
4074 * <p> For <em>line-optimal</em> charsets the stream source's spliterator
4075 * has good splitting properties, assuming the file contains a regular
4076 * sequence of lines. Good splitting properties can result in good parallel
4077 * stream performance. The spliterator for a <em>line-optimal</em> charset
4078 * takes advantage of the charset properties (a line feed or a carriage
4079 * return being efficient identifiable) such that when splitting it can
4080 * approximately divide the number of covered lines in half.
4081 *
4082 * @param path
4083 * the path to the file
4084 * @param cs
4085 * the charset to use for decoding
4086 *
4087 * @return the lines from the file as a {@code Stream}
4088 *
4089 * @throws IOException
4090 * if an I/O error occurs opening the file
4091 * @throws SecurityException
4092 * In the case of the default provider, and a security manager is
4093 * installed, the {@link SecurityManager#checkRead(String) checkRead}
4094 * method is invoked to check read access to the file.
4095 *
4096 * @see #readAllLines(Path, Charset)
4097 * @see #newBufferedReader(Path, Charset)
4098 * @see java.io.BufferedReader#lines()
4099 * @since 1.8
4100 */
4101 public static Stream<String> lines(Path path, Charset cs) throws IOException {
4102 // Use the good splitting spliterator if:
4103 // 1) the path is associated with the default file system;
4104 // 2) the character set is supported; and
4105 // 3) the file size is such that all bytes can be indexed by int values
4106 // (this limitation is imposed by ByteBuffer)
4107 if (path.getFileSystem() == FileSystems.getDefault() &&
4108 FileChannelLinesSpliterator.SUPPORTED_CHARSET_NAMES.contains(cs.name())) {
4109 FileChannel fc = FileChannel.open(path, StandardOpenOption.READ);
4110
4111 Stream<String> fcls = createFileChannelLinesStream(fc, cs);
4112 if (fcls != null) {
4113 return fcls;
4114 }
4115 fc.close();
4116 }
4117
4118 return createBufferedReaderLinesStream(Files.newBufferedReader(path, cs));
4119 }
4120
4121 private static Stream<String> createFileChannelLinesStream(FileChannel fc, Charset cs) throws IOException {
4122 try {
4123 // Obtaining the size from the FileChannel is much faster
4124 // than obtaining using path.toFile().length()
4125 long length = fc.size();
4126 // FileChannel.size() may in certain circumstances return zero
4127 // for a non-zero length file so disallow this case.
4128 if (length > 0 && length <= Integer.MAX_VALUE) {
4129 Spliterator<String> s = new FileChannelLinesSpliterator(fc, cs, 0, (int) length);
4130 return StreamSupport.stream(s, false)
4131 .onClose(Files.asUncheckedRunnable(fc));
4132 }
4133 } catch (Error|RuntimeException|IOException e) {
4134 try {
4135 fc.close();
4136 } catch (IOException ex) {
4137 try {
4138 e.addSuppressed(ex);
4139 } catch (Throwable ignore) {
4140 }
4141 }
4142 throw e;
4143 }
4144 return null;
4145 }
4146
4147 private static Stream<String> createBufferedReaderLinesStream(BufferedReader br) {
4148 try {
4149 return br.lines().onClose(asUncheckedRunnable(br));
4150 } catch (Error|RuntimeException e) {
4151 try {
4152 br.close();
4153 } catch (IOException ex) {
4154 try {
4155 e.addSuppressed(ex);
4156 } catch (Throwable ignore) {
4157 }
4158 }
4159 throw e;
4160 }
4161 }
4162
4163 /**
4164 * Read all lines from a file as a {@code Stream}. Bytes from the file are
4165 * decoded into characters using the {@link StandardCharsets#UTF_8 UTF-8}
4166 * {@link Charset charset}.
4167 *
4168 * <p> The returned stream contains a reference to an open file. The file
4169 * is closed by closing the stream.
4170 *
4171 * <p> The file contents should not be modified during the execution of the
4172 * terminal stream operation. Otherwise, the result of the terminal stream
4173 * operation is undefined.
4174 *
4175 * <p> This method works as if invoking it were equivalent to evaluating the
4176 * expression:
4177 * <pre>{@code
4178 * Files.lines(path, StandardCharsets.UTF_8)
4179 * }</pre>
4180 *
4181 * @apiNote
4182 * This method must be used within a try-with-resources statement or similar
4183 * control structure to ensure that the stream's open file is closed promptly
4184 * after the stream's operations have completed.
4185 *
4186 * @param path
4187 * the path to the file
4188 *
4189 * @return the lines from the file as a {@code Stream}
4190 *
4191 * @throws IOException
4192 * if an I/O error occurs opening the file
4193 * @throws SecurityException
4194 * In the case of the default provider, and a security manager is
4195 * installed, the {@link SecurityManager#checkRead(String) checkRead}
4196 * method is invoked to check read access to the file.
4197 *
4198 * @since 1.8
4199 */
4200 public static Stream<String> lines(Path path) throws IOException {
4201 return lines(path, StandardCharsets.UTF_8);
4202 }
4203 }