1 /*
2 * Copyright (c) 2007, 2018, 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>. The exact
1612 * definition of hidden is platform or provider dependent. On UNIX for
1613 * example a file is considered to be hidden if its name begins with a
1614 * period character ('.'). On Windows a file is considered hidden if it
1615 * isn't a directory and the DOS {@link DosFileAttributes#isHidden hidden}
1616 * attribute is set.
1617 *
1618 * <p> Depending on the implementation this method may require to access
1619 * the file system to determine if the file is considered hidden.
1620 *
1621 * @param path
1622 * the path to the file to test
1623 *
1624 * @return {@code true} if the file is considered hidden
1625 *
1626 * @throws IOException
1627 * if an I/O error occurs
1628 * @throws SecurityException
1629 * In the case of the default provider, and a security manager is
1630 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1631 * method is invoked to check read access to the file.
1632 */
1633 public static boolean isHidden(Path path) throws IOException {
1634 return provider(path).isHidden(path);
1635 }
1636
1637 // lazy loading of default and installed file type detectors
1638 private static class FileTypeDetectors{
1639 static final FileTypeDetector defaultFileTypeDetector =
1640 createDefaultFileTypeDetector();
1641 static final List<FileTypeDetector> installedDetectors =
1642 loadInstalledDetectors();
1643
1644 // creates the default file type detector
1645 private static FileTypeDetector createDefaultFileTypeDetector() {
1646 return AccessController
1647 .doPrivileged(new PrivilegedAction<>() {
1648 @Override public FileTypeDetector run() {
1649 return sun.nio.fs.DefaultFileTypeDetector.create();
1650 }});
1651 }
1652
1653 // loads all installed file type detectors
1654 private static List<FileTypeDetector> loadInstalledDetectors() {
1655 return AccessController
1656 .doPrivileged(new PrivilegedAction<>() {
1657 @Override public List<FileTypeDetector> run() {
1658 List<FileTypeDetector> list = new ArrayList<>();
1659 ServiceLoader<FileTypeDetector> loader = ServiceLoader
1660 .load(FileTypeDetector.class, ClassLoader.getSystemClassLoader());
1661 for (FileTypeDetector detector: loader) {
1662 list.add(detector);
1663 }
1664 return list;
1665 }});
1666 }
1667 }
1668
1669 /**
1670 * Probes the content type of a file.
1671 *
1672 * <p> This method uses the installed {@link FileTypeDetector} implementations
1673 * to probe the given file to determine its content type. Each file type
1674 * detector's {@link FileTypeDetector#probeContentType probeContentType} is
1675 * invoked, in turn, to probe the file type. If the file is recognized then
1676 * the content type is returned. If the file is not recognized by any of the
1677 * installed file type detectors then a system-default file type detector is
1678 * invoked to guess the content type.
1679 *
1680 * <p> A given invocation of the Java virtual machine maintains a system-wide
1681 * list of file type detectors. Installed file type detectors are loaded
1682 * using the service-provider loading facility defined by the {@link ServiceLoader}
1683 * class. Installed file type detectors are loaded using the system class
1684 * loader. If the system class loader cannot be found then the platform class
1685 * loader is used. File type detectors are typically installed
1686 * by placing them in a JAR file on the application class path,
1687 * the JAR file contains a provider-configuration file
1688 * named {@code java.nio.file.spi.FileTypeDetector} in the resource directory
1689 * {@code META-INF/services}, and the file lists one or more fully-qualified
1690 * names of concrete subclass of {@code FileTypeDetector } that have a zero
1691 * argument constructor. If the process of locating or instantiating the
1692 * installed file type detectors fails then an unspecified error is thrown.
1693 * The ordering that installed providers are located is implementation
1694 * specific.
1695 *
1696 * <p> The return value of this method is the string form of the value of a
1697 * Multipurpose Internet Mail Extension (MIME) content type as
1698 * defined by <a href="http://www.ietf.org/rfc/rfc2045.txt"><i>RFC 2045:
1699 * Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet
1700 * Message Bodies</i></a>. The string is guaranteed to be parsable according
1701 * to the grammar in the RFC.
1702 *
1703 * @param path
1704 * the path to the file to probe
1705 *
1706 * @return The content type of the file, or {@code null} if the content
1707 * type cannot be determined
1708 *
1709 * @throws IOException
1710 * if an I/O error occurs
1711 * @throws SecurityException
1712 * If a security manager is installed and it denies an unspecified
1713 * permission required by a file type detector implementation.
1714 */
1715 public static String probeContentType(Path path)
1716 throws IOException
1717 {
1718 // try installed file type detectors
1719 for (FileTypeDetector detector: FileTypeDetectors.installedDetectors) {
1720 String result = detector.probeContentType(path);
1721 if (result != null)
1722 return result;
1723 }
1724
1725 // fallback to default
1726 return FileTypeDetectors.defaultFileTypeDetector.probeContentType(path);
1727 }
1728
1729 // -- File Attributes --
1730
1731 /**
1732 * Returns a file attribute view of a given type.
1733 *
1734 * <p> A file attribute view provides a read-only or updatable view of a
1735 * set of file attributes. This method is intended to be used where the file
1736 * attribute view defines type-safe methods to read or update the file
1737 * attributes. The {@code type} parameter is the type of the attribute view
1738 * required and the method returns an instance of that type if supported.
1739 * The {@link BasicFileAttributeView} type supports access to the basic
1740 * attributes of a file. Invoking this method to select a file attribute
1741 * view of that type will always return an instance of that class.
1742 *
1743 * <p> The {@code options} array may be used to indicate how symbolic links
1744 * are handled by the resulting file attribute view for the case that the
1745 * file is a symbolic link. By default, symbolic links are followed. If the
1746 * option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is present then
1747 * symbolic links are not followed. This option is ignored by implementations
1748 * that do not support symbolic links.
1749 *
1750 * <p> <b>Usage Example:</b>
1751 * Suppose we want read or set a file's ACL, if supported:
1752 * <pre>
1753 * Path path = ...
1754 * AclFileAttributeView view = Files.getFileAttributeView(path, AclFileAttributeView.class);
1755 * if (view != null) {
1756 * List<AclEntry> acl = view.getAcl();
1757 * :
1758 * }
1759 * </pre>
1760 *
1761 * @param <V>
1762 * The {@code FileAttributeView} type
1763 * @param path
1764 * the path to the file
1765 * @param type
1766 * the {@code Class} object corresponding to the file attribute view
1767 * @param options
1768 * options indicating how symbolic links are handled
1769 *
1770 * @return a file attribute view of the specified type, or {@code null} if
1771 * the attribute view type is not available
1772 */
1773 public static <V extends FileAttributeView> V getFileAttributeView(Path path,
1774 Class<V> type,
1775 LinkOption... options)
1776 {
1777 return provider(path).getFileAttributeView(path, type, options);
1778 }
1779
1780 /**
1781 * Reads a file's attributes as a bulk operation.
1782 *
1783 * <p> The {@code type} parameter is the type of the attributes required
1784 * and this method returns an instance of that type if supported. All
1785 * implementations support a basic set of file attributes and so invoking
1786 * this method with a {@code type} parameter of {@code
1787 * BasicFileAttributes.class} will not throw {@code
1788 * UnsupportedOperationException}.
1789 *
1790 * <p> The {@code options} array may be used to indicate how symbolic links
1791 * are handled for the case that the file is a symbolic link. By default,
1792 * symbolic links are followed and the file attribute of the final target
1793 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1794 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1795 *
1796 * <p> It is implementation specific if all file attributes are read as an
1797 * atomic operation with respect to other file system operations.
1798 *
1799 * <p> <b>Usage Example:</b>
1800 * Suppose we want to read a file's attributes in bulk:
1801 * <pre>
1802 * Path path = ...
1803 * BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class);
1804 * </pre>
1805 * Alternatively, suppose we want to read file's POSIX attributes without
1806 * following symbolic links:
1807 * <pre>
1808 * PosixFileAttributes attrs =
1809 * Files.readAttributes(path, PosixFileAttributes.class, NOFOLLOW_LINKS);
1810 * </pre>
1811 *
1812 * @param <A>
1813 * The {@code BasicFileAttributes} type
1814 * @param path
1815 * the path to the file
1816 * @param type
1817 * the {@code Class} of the file attributes required
1818 * to read
1819 * @param options
1820 * options indicating how symbolic links are handled
1821 *
1822 * @return the file attributes
1823 *
1824 * @throws UnsupportedOperationException
1825 * if an attributes of the given type are not supported
1826 * @throws IOException
1827 * if an I/O error occurs
1828 * @throws SecurityException
1829 * In the case of the default provider, a security manager is
1830 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1831 * method is invoked to check read access to the file. If this
1832 * method is invoked to read security sensitive attributes then the
1833 * security manager may be invoke to check for additional permissions.
1834 */
1835 public static <A extends BasicFileAttributes> A readAttributes(Path path,
1836 Class<A> type,
1837 LinkOption... options)
1838 throws IOException
1839 {
1840 return provider(path).readAttributes(path, type, options);
1841 }
1842
1843 /**
1844 * Sets the value of a file attribute.
1845 *
1846 * <p> The {@code attribute} parameter identifies the attribute to be set
1847 * and takes the form:
1848 * <blockquote>
1849 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
1850 * </blockquote>
1851 * where square brackets [...] delineate an optional component and the
1852 * character {@code ':'} stands for itself.
1853 *
1854 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1855 * FileAttributeView} that identifies a set of file attributes. If not
1856 * specified then it defaults to {@code "basic"}, the name of the file
1857 * attribute view that identifies the basic set of file attributes common to
1858 * many file systems. <i>attribute-name</i> is the name of the attribute
1859 * within the set.
1860 *
1861 * <p> The {@code options} array may be used to indicate how symbolic links
1862 * are handled for the case that the file is a symbolic link. By default,
1863 * symbolic links are followed and the file attribute of the final target
1864 * of the link is set. If the option {@link LinkOption#NOFOLLOW_LINKS
1865 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1866 *
1867 * <p> <b>Usage Example:</b>
1868 * Suppose we want to set the DOS "hidden" attribute:
1869 * <pre>
1870 * Path path = ...
1871 * Files.setAttribute(path, "dos:hidden", true);
1872 * </pre>
1873 *
1874 * @param path
1875 * the path to the file
1876 * @param attribute
1877 * the attribute to set
1878 * @param value
1879 * the attribute value
1880 * @param options
1881 * options indicating how symbolic links are handled
1882 *
1883 * @return the given path
1884 *
1885 * @throws UnsupportedOperationException
1886 * if the attribute view is not available
1887 * @throws IllegalArgumentException
1888 * if the attribute name is not specified, or is not recognized, or
1889 * the attribute value is of the correct type but has an
1890 * inappropriate value
1891 * @throws ClassCastException
1892 * if the attribute value is not of the expected type or is a
1893 * collection containing elements that are not of the expected
1894 * type
1895 * @throws IOException
1896 * if an I/O error occurs
1897 * @throws SecurityException
1898 * In the case of the default provider, and a security manager is
1899 * installed, its {@link SecurityManager#checkWrite(String) checkWrite}
1900 * method denies write access to the file. If this method is invoked
1901 * to set security sensitive attributes then the security manager
1902 * may be invoked to check for additional permissions.
1903 */
1904 public static Path setAttribute(Path path, String attribute, Object value,
1905 LinkOption... options)
1906 throws IOException
1907 {
1908 provider(path).setAttribute(path, attribute, value, options);
1909 return path;
1910 }
1911
1912 /**
1913 * Reads the value of a file attribute.
1914 *
1915 * <p> The {@code attribute} parameter identifies the attribute to be read
1916 * and takes the form:
1917 * <blockquote>
1918 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
1919 * </blockquote>
1920 * where square brackets [...] delineate an optional component and the
1921 * character {@code ':'} stands for itself.
1922 *
1923 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1924 * FileAttributeView} that identifies a set of file attributes. If not
1925 * specified then it defaults to {@code "basic"}, the name of the file
1926 * attribute view that identifies the basic set of file attributes common to
1927 * many file systems. <i>attribute-name</i> is the name of the attribute.
1928 *
1929 * <p> The {@code options} array may be used to indicate how symbolic links
1930 * are handled for the case that the file is a symbolic link. By default,
1931 * symbolic links are followed and the file attribute of the final target
1932 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1933 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1934 *
1935 * <p> <b>Usage Example:</b>
1936 * Suppose we require the user ID of the file owner on a system that
1937 * supports a "{@code unix}" view:
1938 * <pre>
1939 * Path path = ...
1940 * int uid = (Integer)Files.getAttribute(path, "unix:uid");
1941 * </pre>
1942 *
1943 * @param path
1944 * the path to the file
1945 * @param attribute
1946 * the attribute to read
1947 * @param options
1948 * options indicating how symbolic links are handled
1949 *
1950 * @return the attribute value
1951 *
1952 * @throws UnsupportedOperationException
1953 * if the attribute view is not available
1954 * @throws IllegalArgumentException
1955 * if the attribute name is not specified or is not recognized
1956 * @throws IOException
1957 * if an I/O error occurs
1958 * @throws SecurityException
1959 * In the case of the default provider, and a security manager is
1960 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1961 * method denies read access to the file. If this method is invoked
1962 * to read security sensitive attributes then the security manager
1963 * may be invoked to check for additional permissions.
1964 */
1965 public static Object getAttribute(Path path, String attribute,
1966 LinkOption... options)
1967 throws IOException
1968 {
1969 // only one attribute should be read
1970 if (attribute.indexOf('*') >= 0 || attribute.indexOf(',') >= 0)
1971 throw new IllegalArgumentException(attribute);
1972 Map<String,Object> map = readAttributes(path, attribute, options);
1973 assert map.size() == 1;
1974 String name;
1975 int pos = attribute.indexOf(':');
1976 if (pos == -1) {
1977 name = attribute;
1978 } else {
1979 name = (pos == attribute.length()) ? "" : attribute.substring(pos+1);
1980 }
1981 return map.get(name);
1982 }
1983
1984 /**
1985 * Reads a set of file attributes as a bulk operation.
1986 *
1987 * <p> The {@code attributes} parameter identifies the attributes to be read
1988 * and takes the form:
1989 * <blockquote>
1990 * [<i>view-name</i><b>:</b>]<i>attribute-list</i>
1991 * </blockquote>
1992 * where square brackets [...] delineate an optional component and the
1993 * character {@code ':'} stands for itself.
1994 *
1995 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1996 * FileAttributeView} that identifies a set of file attributes. If not
1997 * specified then it defaults to {@code "basic"}, the name of the file
1998 * attribute view that identifies the basic set of file attributes common to
1999 * many file systems.
2000 *
2001 * <p> The <i>attribute-list</i> component is a comma separated list of
2002 * one or more names of attributes to read. If the list contains the value
2003 * {@code "*"} then all attributes are read. Attributes that are not supported
2004 * are ignored and will not be present in the returned map. It is
2005 * implementation specific if all attributes are read as an atomic operation
2006 * with respect to other file system operations.
2007 *
2008 * <p> The following examples demonstrate possible values for the {@code
2009 * attributes} parameter:
2010 *
2011 * <table class="striped" style="text-align: left; margin-left:2em">
2012 * <caption style="display:none">Possible values</caption>
2013 * <thead>
2014 * <tr>
2015 * <th scope="col">Example
2016 * <th scope="col">Description
2017 * </thead>
2018 * <tbody>
2019 * <tr>
2020 * <th scope="row"> {@code "*"} </th>
2021 * <td> Read all {@link BasicFileAttributes basic-file-attributes}. </td>
2022 * </tr>
2023 * <tr>
2024 * <th scope="row"> {@code "size,lastModifiedTime,lastAccessTime"} </th>
2025 * <td> Reads the file size, last modified time, and last access time
2026 * attributes. </td>
2027 * </tr>
2028 * <tr>
2029 * <th scope="row"> {@code "posix:*"} </th>
2030 * <td> Read all {@link PosixFileAttributes POSIX-file-attributes}. </td>
2031 * </tr>
2032 * <tr>
2033 * <th scope="row"> {@code "posix:permissions,owner,size"} </th>
2034 * <td> Reads the POSIX file permissions, owner, and file size. </td>
2035 * </tr>
2036 * </tbody>
2037 * </table>
2038 *
2039 * <p> The {@code options} array may be used to indicate how symbolic links
2040 * are handled for the case that the file is a symbolic link. By default,
2041 * symbolic links are followed and the file attribute of the final target
2042 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2043 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2044 *
2045 * @param path
2046 * the path to the file
2047 * @param attributes
2048 * the attributes to read
2049 * @param options
2050 * options indicating how symbolic links are handled
2051 *
2052 * @return a map of the attributes returned; The map's keys are the
2053 * attribute names, its values are the attribute values
2054 *
2055 * @throws UnsupportedOperationException
2056 * if the attribute view is not available
2057 * @throws IllegalArgumentException
2058 * if no attributes are specified or an unrecognized attribute is
2059 * specified
2060 * @throws IOException
2061 * if an I/O error occurs
2062 * @throws SecurityException
2063 * In the case of the default provider, and a security manager is
2064 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2065 * method denies read access to the file. If this method is invoked
2066 * to read security sensitive attributes then the security manager
2067 * may be invoke to check for additional permissions.
2068 */
2069 public static Map<String,Object> readAttributes(Path path, String attributes,
2070 LinkOption... options)
2071 throws IOException
2072 {
2073 return provider(path).readAttributes(path, attributes, options);
2074 }
2075
2076 /**
2077 * Returns a file's POSIX file permissions.
2078 *
2079 * <p> The {@code path} parameter is associated with a {@code FileSystem}
2080 * that supports the {@link PosixFileAttributeView}. This attribute view
2081 * provides access to file attributes commonly associated with files on file
2082 * systems used by operating systems that implement the Portable Operating
2083 * System Interface (POSIX) family of standards.
2084 *
2085 * <p> The {@code options} array may be used to indicate how symbolic links
2086 * are handled for the case that the file is a symbolic link. By default,
2087 * symbolic links are followed and the file attribute of the final target
2088 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2089 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2090 *
2091 * @param path
2092 * the path to the file
2093 * @param options
2094 * options indicating how symbolic links are handled
2095 *
2096 * @return the file permissions
2097 *
2098 * @throws UnsupportedOperationException
2099 * if the associated file system does not support the {@code
2100 * PosixFileAttributeView}
2101 * @throws IOException
2102 * if an I/O error occurs
2103 * @throws SecurityException
2104 * In the case of the default provider, a security manager is
2105 * installed, and it denies
2106 * {@link RuntimePermission}{@code ("accessUserInformation")}
2107 * or its {@link SecurityManager#checkRead(String) checkRead} method
2108 * denies read access to the file.
2109 */
2110 public static Set<PosixFilePermission> getPosixFilePermissions(Path path,
2111 LinkOption... options)
2112 throws IOException
2113 {
2114 return readAttributes(path, PosixFileAttributes.class, options).permissions();
2115 }
2116
2117 /**
2118 * Sets a file's POSIX permissions.
2119 *
2120 * <p> The {@code path} parameter is associated with a {@code FileSystem}
2121 * that supports the {@link PosixFileAttributeView}. This attribute view
2122 * provides access to file attributes commonly associated with files on file
2123 * systems used by operating systems that implement the Portable Operating
2124 * System Interface (POSIX) family of standards.
2125 *
2126 * @param path
2127 * The path to the file
2128 * @param perms
2129 * The new set of permissions
2130 *
2131 * @return The given path
2132 *
2133 * @throws UnsupportedOperationException
2134 * if the associated file system does not support the {@code
2135 * PosixFileAttributeView}
2136 * @throws ClassCastException
2137 * if the sets contains elements that are not of type {@code
2138 * PosixFilePermission}
2139 * @throws IOException
2140 * if an I/O error occurs
2141 * @throws SecurityException
2142 * In the case of the default provider, and a security manager is
2143 * installed, it denies
2144 * {@link RuntimePermission}{@code ("accessUserInformation")}
2145 * or its {@link SecurityManager#checkWrite(String) checkWrite}
2146 * method denies write access to the file.
2147 */
2148 public static Path setPosixFilePermissions(Path path,
2149 Set<PosixFilePermission> perms)
2150 throws IOException
2151 {
2152 PosixFileAttributeView view =
2153 getFileAttributeView(path, PosixFileAttributeView.class);
2154 if (view == null)
2155 throw new UnsupportedOperationException();
2156 view.setPermissions(perms);
2157 return path;
2158 }
2159
2160 /**
2161 * Returns the owner of a file.
2162 *
2163 * <p> The {@code path} parameter is associated with a file system that
2164 * supports {@link FileOwnerAttributeView}. This file attribute view provides
2165 * access to a file attribute that is the owner of the file.
2166 *
2167 * @param path
2168 * The path to the file
2169 * @param options
2170 * options indicating how symbolic links are handled
2171 *
2172 * @return A user principal representing the owner of the file
2173 *
2174 * @throws UnsupportedOperationException
2175 * if the associated file system does not support the {@code
2176 * FileOwnerAttributeView}
2177 * @throws IOException
2178 * if an I/O error occurs
2179 * @throws SecurityException
2180 * In the case of the default provider, and a security manager is
2181 * installed, it denies
2182 * {@link RuntimePermission}{@code ("accessUserInformation")}
2183 * or its {@link SecurityManager#checkRead(String) checkRead} method
2184 * denies read access to the file.
2185 */
2186 public static UserPrincipal getOwner(Path path, LinkOption... options) throws IOException {
2187 FileOwnerAttributeView view =
2188 getFileAttributeView(path, FileOwnerAttributeView.class, options);
2189 if (view == null)
2190 throw new UnsupportedOperationException();
2191 return view.getOwner();
2192 }
2193
2194 /**
2195 * Updates the file owner.
2196 *
2197 * <p> The {@code path} parameter is associated with a file system that
2198 * supports {@link FileOwnerAttributeView}. This file attribute view provides
2199 * access to a file attribute that is the owner of the file.
2200 *
2201 * <p> <b>Usage Example:</b>
2202 * Suppose we want to make "joe" the owner of a file:
2203 * <pre>
2204 * Path path = ...
2205 * UserPrincipalLookupService lookupService =
2206 * provider(path).getUserPrincipalLookupService();
2207 * UserPrincipal joe = lookupService.lookupPrincipalByName("joe");
2208 * Files.setOwner(path, joe);
2209 * </pre>
2210 *
2211 * @param path
2212 * The path to the file
2213 * @param owner
2214 * The new file owner
2215 *
2216 * @return The given path
2217 *
2218 * @throws UnsupportedOperationException
2219 * if the associated file system does not support the {@code
2220 * FileOwnerAttributeView}
2221 * @throws IOException
2222 * if an I/O error occurs
2223 * @throws SecurityException
2224 * In the case of the default provider, and a security manager is
2225 * installed, it denies
2226 * {@link RuntimePermission}{@code ("accessUserInformation")}
2227 * or its {@link SecurityManager#checkWrite(String) checkWrite}
2228 * method denies write access to the file.
2229 *
2230 * @see FileSystem#getUserPrincipalLookupService
2231 * @see java.nio.file.attribute.UserPrincipalLookupService
2232 */
2233 public static Path setOwner(Path path, UserPrincipal owner)
2234 throws IOException
2235 {
2236 FileOwnerAttributeView view =
2237 getFileAttributeView(path, FileOwnerAttributeView.class);
2238 if (view == null)
2239 throw new UnsupportedOperationException();
2240 view.setOwner(owner);
2241 return path;
2242 }
2243
2244 /**
2245 * Tests whether a file is a symbolic link.
2246 *
2247 * <p> Where it is required to distinguish an I/O exception from the case
2248 * that the file is not a symbolic link then the file attributes can be
2249 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2250 * readAttributes} method and the file type tested with the {@link
2251 * BasicFileAttributes#isSymbolicLink} method.
2252 *
2253 * @param path The path to the file
2254 *
2255 * @return {@code true} if the file is a symbolic link; {@code false} if
2256 * the file does not exist, is not a symbolic link, or it cannot
2257 * be determined if the file is a symbolic link or not.
2258 *
2259 * @throws SecurityException
2260 * In the case of the default provider, and a security manager is
2261 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2262 * method denies read access to the file.
2263 */
2264 public static boolean isSymbolicLink(Path path) {
2265 try {
2266 return readAttributes(path,
2267 BasicFileAttributes.class,
2268 LinkOption.NOFOLLOW_LINKS).isSymbolicLink();
2269 } catch (IOException ioe) {
2270 return false;
2271 }
2272 }
2273
2274 /**
2275 * Tests whether a file is a directory.
2276 *
2277 * <p> The {@code options} array may be used to indicate how symbolic links
2278 * are handled for the case that the file is a symbolic link. By default,
2279 * symbolic links are followed and the file attribute of the final target
2280 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2281 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2282 *
2283 * <p> Where it is required to distinguish an I/O exception from the case
2284 * that the file is not a directory then the file attributes can be
2285 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2286 * readAttributes} method and the file type tested with the {@link
2287 * BasicFileAttributes#isDirectory} method.
2288 *
2289 * @param path
2290 * the path to the file to test
2291 * @param options
2292 * options indicating how symbolic links are handled
2293 *
2294 * @return {@code true} if the file is a directory; {@code false} if
2295 * the file does not exist, is not a directory, or it cannot
2296 * be determined if the file is a directory or not.
2297 *
2298 * @throws SecurityException
2299 * In the case of the default provider, and a security manager is
2300 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2301 * method denies read access to the file.
2302 */
2303 public static boolean isDirectory(Path path, LinkOption... options) {
2304 if (options.length == 0) {
2305 FileSystemProvider provider = provider(path);
2306 if (provider instanceof AbstractFileSystemProvider)
2307 return ((AbstractFileSystemProvider)provider).isDirectory(path);
2308 }
2309
2310 try {
2311 return readAttributes(path, BasicFileAttributes.class, options).isDirectory();
2312 } catch (IOException ioe) {
2313 return false;
2314 }
2315 }
2316
2317 /**
2318 * Tests whether a file is a regular file with opaque content.
2319 *
2320 * <p> The {@code options} array may be used to indicate how symbolic links
2321 * are handled for the case that the file is a symbolic link. By default,
2322 * symbolic links are followed and the file attribute of the final target
2323 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2324 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2325 *
2326 * <p> Where it is required to distinguish an I/O exception from the case
2327 * that the file is not a regular file then the file attributes can be
2328 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2329 * readAttributes} method and the file type tested with the {@link
2330 * BasicFileAttributes#isRegularFile} method.
2331 *
2332 * @param path
2333 * the path to the file
2334 * @param options
2335 * options indicating how symbolic links are handled
2336 *
2337 * @return {@code true} if the file is a regular file; {@code false} if
2338 * the file does not exist, is not a regular file, or it
2339 * cannot be determined if the file is a regular file or not.
2340 *
2341 * @throws SecurityException
2342 * In the case of the default provider, and a security manager is
2343 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2344 * method denies read access to the file.
2345 */
2346 public static boolean isRegularFile(Path path, LinkOption... options) {
2347 if (options.length == 0) {
2348 FileSystemProvider provider = provider(path);
2349 if (provider instanceof AbstractFileSystemProvider)
2350 return ((AbstractFileSystemProvider)provider).isRegularFile(path);
2351 }
2352
2353 try {
2354 return readAttributes(path, BasicFileAttributes.class, options).isRegularFile();
2355 } catch (IOException ioe) {
2356 return false;
2357 }
2358 }
2359
2360 /**
2361 * Returns a file's last modified time.
2362 *
2363 * <p> The {@code options} array may be used to indicate how symbolic links
2364 * are handled for the case that the file is a symbolic link. By default,
2365 * symbolic links are followed and the file attribute of the final target
2366 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2367 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2368 *
2369 * @param path
2370 * the path to the file
2371 * @param options
2372 * options indicating how symbolic links are handled
2373 *
2374 * @return a {@code FileTime} representing the time the file was last
2375 * modified, or an implementation specific default when a time
2376 * stamp to indicate the time of last modification is not supported
2377 * by the file system
2378 *
2379 * @throws IOException
2380 * if an I/O error occurs
2381 * @throws SecurityException
2382 * In the case of the default provider, and a security manager is
2383 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2384 * method denies read access to the file.
2385 *
2386 * @see BasicFileAttributes#lastModifiedTime
2387 */
2388 public static FileTime getLastModifiedTime(Path path, LinkOption... options)
2389 throws IOException
2390 {
2391 return readAttributes(path, BasicFileAttributes.class, options).lastModifiedTime();
2392 }
2393
2394 /**
2395 * Updates a file's last modified time attribute. The file time is converted
2396 * to the epoch and precision supported by the file system. Converting from
2397 * finer to coarser granularities result in precision loss. The behavior of
2398 * this method when attempting to set the last modified time when it is not
2399 * supported by the file system or is outside the range supported by the
2400 * underlying file store is not defined. It may or not fail by throwing an
2401 * {@code IOException}.
2402 *
2403 * <p> <b>Usage Example:</b>
2404 * Suppose we want to set the last modified time to the current time:
2405 * <pre>
2406 * Path path = ...
2407 * FileTime now = FileTime.fromMillis(System.currentTimeMillis());
2408 * Files.setLastModifiedTime(path, now);
2409 * </pre>
2410 *
2411 * @param path
2412 * the path to the file
2413 * @param time
2414 * the new last modified time
2415 *
2416 * @return the given path
2417 *
2418 * @throws IOException
2419 * if an I/O error occurs
2420 * @throws SecurityException
2421 * In the case of the default provider, and a security manager is
2422 * installed, its {@link SecurityManager#checkWrite(String)
2423 * checkWrite} method denies write access to the file.
2424 *
2425 * @see BasicFileAttributeView#setTimes
2426 */
2427 public static Path setLastModifiedTime(Path path, FileTime time)
2428 throws IOException
2429 {
2430 getFileAttributeView(path, BasicFileAttributeView.class)
2431 .setTimes(Objects.requireNonNull(time), null, null);
2432 return path;
2433 }
2434
2435 /**
2436 * Returns the size of a file (in bytes). The size may differ from the
2437 * actual size on the file system due to compression, support for sparse
2438 * files, or other reasons. The size of files that are not {@link
2439 * #isRegularFile regular} files is implementation specific and
2440 * therefore unspecified.
2441 *
2442 * @param path
2443 * the path to the file
2444 *
2445 * @return the file size, in bytes
2446 *
2447 * @throws IOException
2448 * if an I/O error occurs
2449 * @throws SecurityException
2450 * In the case of the default provider, and a security manager is
2451 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2452 * method denies read access to the file.
2453 *
2454 * @see BasicFileAttributes#size
2455 */
2456 public static long size(Path path) throws IOException {
2457 return readAttributes(path, BasicFileAttributes.class).size();
2458 }
2459
2460 // -- Accessibility --
2461
2462 /**
2463 * Returns {@code false} if NOFOLLOW_LINKS is present.
2464 */
2465 private static boolean followLinks(LinkOption... options) {
2466 boolean followLinks = true;
2467 for (LinkOption opt: options) {
2468 if (opt == LinkOption.NOFOLLOW_LINKS) {
2469 followLinks = false;
2470 continue;
2471 }
2472 if (opt == null)
2473 throw new NullPointerException();
2474 throw new AssertionError("Should not get here");
2475 }
2476 return followLinks;
2477 }
2478
2479 /**
2480 * Tests whether a file exists.
2481 *
2482 * <p> The {@code options} parameter may be used to indicate how symbolic links
2483 * are handled for the case that the file is a symbolic link. By default,
2484 * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
2485 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2486 *
2487 * <p> Note that the result of this method is immediately outdated. If this
2488 * method indicates the file exists then there is no guarantee that a
2489 * subsequent access will succeed. Care should be taken when using this
2490 * method in security sensitive applications.
2491 *
2492 * @param path
2493 * the path to the file to test
2494 * @param options
2495 * options indicating how symbolic links are handled
2496 * .
2497 * @return {@code true} if the file exists; {@code false} if the file does
2498 * not exist or its existence cannot be determined.
2499 *
2500 * @throws SecurityException
2501 * In the case of the default provider, the {@link
2502 * SecurityManager#checkRead(String)} is invoked to check
2503 * read access to the file.
2504 *
2505 * @see #notExists
2506 */
2507 public static boolean exists(Path path, LinkOption... options) {
2508 if (options.length == 0) {
2509 FileSystemProvider provider = provider(path);
2510 if (provider instanceof AbstractFileSystemProvider)
2511 return ((AbstractFileSystemProvider)provider).exists(path);
2512 }
2513
2514 try {
2515 if (followLinks(options)) {
2516 provider(path).checkAccess(path);
2517 } else {
2518 // attempt to read attributes without following links
2519 readAttributes(path, BasicFileAttributes.class,
2520 LinkOption.NOFOLLOW_LINKS);
2521 }
2522 // file exists
2523 return true;
2524 } catch (IOException x) {
2525 // does not exist or unable to determine if file exists
2526 return false;
2527 }
2528
2529 }
2530
2531 /**
2532 * Tests whether the file located by this path does not exist. This method
2533 * is intended for cases where it is required to take action when it can be
2534 * confirmed that a file does not exist.
2535 *
2536 * <p> The {@code options} parameter may be used to indicate how symbolic links
2537 * are handled for the case that the file is a symbolic link. By default,
2538 * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
2539 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2540 *
2541 * <p> Note that this method is not the complement of the {@link #exists
2542 * exists} method. Where it is not possible to determine if a file exists
2543 * or not then both methods return {@code false}. As with the {@code exists}
2544 * method, the result of this method is immediately outdated. If this
2545 * method indicates the file does exist then there is no guarantee that a
2546 * subsequent attempt to create the file will succeed. Care should be taken
2547 * when using this method in security sensitive applications.
2548 *
2549 * @param path
2550 * the path to the file to test
2551 * @param options
2552 * options indicating how symbolic links are handled
2553 *
2554 * @return {@code true} if the file does not exist; {@code false} if the
2555 * file exists or its existence cannot be determined
2556 *
2557 * @throws SecurityException
2558 * In the case of the default provider, the {@link
2559 * SecurityManager#checkRead(String)} is invoked to check
2560 * read access to the file.
2561 */
2562 public static boolean notExists(Path path, LinkOption... options) {
2563 try {
2564 if (followLinks(options)) {
2565 provider(path).checkAccess(path);
2566 } else {
2567 // attempt to read attributes without following links
2568 readAttributes(path, BasicFileAttributes.class,
2569 LinkOption.NOFOLLOW_LINKS);
2570 }
2571 // file exists
2572 return false;
2573 } catch (NoSuchFileException x) {
2574 // file confirmed not to exist
2575 return true;
2576 } catch (IOException x) {
2577 return false;
2578 }
2579 }
2580
2581 /**
2582 * Used by isReadable, isWritable, isExecutable to test access to a file.
2583 */
2584 private static boolean isAccessible(Path path, AccessMode... modes) {
2585 try {
2586 provider(path).checkAccess(path, modes);
2587 return true;
2588 } catch (IOException x) {
2589 return false;
2590 }
2591 }
2592
2593 /**
2594 * Tests whether a file is readable. This method checks that a file exists
2595 * and that this Java virtual machine has appropriate privileges that would
2596 * allow it open the file for reading. Depending on the implementation, this
2597 * method may require to read file permissions, access control lists, or
2598 * other file attributes in order to check the effective access to the file.
2599 * Consequently, this method may not be atomic with respect to other file
2600 * system operations.
2601 *
2602 * <p> Note that the result of this method is immediately outdated, there is
2603 * no guarantee that a subsequent attempt to open the file for reading will
2604 * succeed (or even that it will access the same file). Care should be taken
2605 * when using this method in security sensitive applications.
2606 *
2607 * @param path
2608 * the path to the file to check
2609 *
2610 * @return {@code true} if the file exists and is readable; {@code false}
2611 * if the file does not exist, read access would be denied because
2612 * the Java virtual machine has insufficient privileges, or access
2613 * cannot be determined
2614 *
2615 * @throws SecurityException
2616 * In the case of the default provider, and a security manager is
2617 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2618 * is invoked to check read access to the file.
2619 */
2620 public static boolean isReadable(Path path) {
2621 return isAccessible(path, AccessMode.READ);
2622 }
2623
2624 /**
2625 * Tests whether a file is writable. This method checks that a file exists
2626 * and that this Java virtual machine has appropriate privileges that would
2627 * allow it open the file for writing. Depending on the implementation, this
2628 * method may require to read file permissions, access control lists, or
2629 * other file attributes in order to check the effective access to the file.
2630 * Consequently, this method may not be atomic with respect to other file
2631 * system operations.
2632 *
2633 * <p> Note that result of this method is immediately outdated, there is no
2634 * guarantee that a subsequent attempt to open the file for writing will
2635 * succeed (or even that it will access the same file). Care should be taken
2636 * when using this method in security sensitive applications.
2637 *
2638 * @param path
2639 * the path to the file to check
2640 *
2641 * @return {@code true} if the file exists and is writable; {@code false}
2642 * if the file does not exist, write access would be denied because
2643 * the Java virtual machine has insufficient privileges, or access
2644 * cannot be determined
2645 *
2646 * @throws SecurityException
2647 * In the case of the default provider, and a security manager is
2648 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2649 * is invoked to check write access to the file.
2650 */
2651 public static boolean isWritable(Path path) {
2652 return isAccessible(path, AccessMode.WRITE);
2653 }
2654
2655 /**
2656 * Tests whether a file is executable. This method checks that a file exists
2657 * and that this Java virtual machine has appropriate privileges to {@link
2658 * Runtime#exec execute} the file. The semantics may differ when checking
2659 * access to a directory. For example, on UNIX systems, checking for
2660 * execute access checks that the Java virtual machine has permission to
2661 * search the directory in order to access file or subdirectories.
2662 *
2663 * <p> Depending on the implementation, this method may require to read file
2664 * permissions, access control lists, or other file attributes in order to
2665 * check the effective access to the file. Consequently, this method may not
2666 * be atomic with respect to other file system operations.
2667 *
2668 * <p> Note that the result of this method is immediately outdated, there is
2669 * no guarantee that a subsequent attempt to execute the file will succeed
2670 * (or even that it will access the same file). Care should be taken when
2671 * using this method in security sensitive applications.
2672 *
2673 * @param path
2674 * the path to the file to check
2675 *
2676 * @return {@code true} if the file exists and is executable; {@code false}
2677 * if the file does not exist, execute access would be denied because
2678 * the Java virtual machine has insufficient privileges, or access
2679 * cannot be determined
2680 *
2681 * @throws SecurityException
2682 * In the case of the default provider, and a security manager is
2683 * installed, the {@link SecurityManager#checkExec(String)
2684 * checkExec} is invoked to check execute access to the file.
2685 */
2686 public static boolean isExecutable(Path path) {
2687 return isAccessible(path, AccessMode.EXECUTE);
2688 }
2689
2690 // -- Recursive operations --
2691
2692 /**
2693 * Walks a file tree.
2694 *
2695 * <p> This method walks a file tree rooted at a given starting file. The
2696 * file tree traversal is <em>depth-first</em> with the given {@link
2697 * FileVisitor} invoked for each file encountered. File tree traversal
2698 * completes when all accessible files in the tree have been visited, or a
2699 * visit method returns a result of {@link FileVisitResult#TERMINATE
2700 * TERMINATE}. Where a visit method terminates due an {@code IOException},
2701 * an uncaught error, or runtime exception, then the traversal is terminated
2702 * and the error or exception is propagated to the caller of this method.
2703 *
2704 * <p> For each file encountered this method attempts to read its {@link
2705 * java.nio.file.attribute.BasicFileAttributes}. If the file is not a
2706 * directory then the {@link FileVisitor#visitFile visitFile} method is
2707 * invoked with the file attributes. If the file attributes cannot be read,
2708 * due to an I/O exception, then the {@link FileVisitor#visitFileFailed
2709 * visitFileFailed} method is invoked with the I/O exception.
2710 *
2711 * <p> Where the file is a directory, and the directory could not be opened,
2712 * then the {@code visitFileFailed} method is invoked with the I/O exception,
2713 * after which, the file tree walk continues, by default, at the next
2714 * <em>sibling</em> of the directory.
2715 *
2716 * <p> Where the directory is opened successfully, then the entries in the
2717 * directory, and their <em>descendants</em> are visited. When all entries
2718 * have been visited, or an I/O error occurs during iteration of the
2719 * directory, then the directory is closed and the visitor's {@link
2720 * FileVisitor#postVisitDirectory postVisitDirectory} method is invoked.
2721 * The file tree walk then continues, by default, at the next <em>sibling</em>
2722 * of the directory.
2723 *
2724 * <p> By default, symbolic links are not automatically followed by this
2725 * method. If the {@code options} parameter contains the {@link
2726 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then symbolic links are
2727 * followed. When following links, and the attributes of the target cannot
2728 * be read, then this method attempts to get the {@code BasicFileAttributes}
2729 * of the link. If they can be read then the {@code visitFile} method is
2730 * invoked with the attributes of the link (otherwise the {@code visitFileFailed}
2731 * method is invoked as specified above).
2732 *
2733 * <p> If the {@code options} parameter contains the {@link
2734 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then this method keeps
2735 * track of directories visited so that cycles can be detected. A cycle
2736 * arises when there is an entry in a directory that is an ancestor of the
2737 * directory. Cycle detection is done by recording the {@link
2738 * java.nio.file.attribute.BasicFileAttributes#fileKey file-key} of directories,
2739 * or if file keys are not available, by invoking the {@link #isSameFile
2740 * isSameFile} method to test if a directory is the same file as an
2741 * ancestor. When a cycle is detected it is treated as an I/O error, and the
2742 * {@link FileVisitor#visitFileFailed visitFileFailed} method is invoked with
2743 * an instance of {@link FileSystemLoopException}.
2744 *
2745 * <p> The {@code maxDepth} parameter is the maximum number of levels of
2746 * directories to visit. A value of {@code 0} means that only the starting
2747 * file is visited, unless denied by the security manager. A value of
2748 * {@link Integer#MAX_VALUE MAX_VALUE} may be used to indicate that all
2749 * levels should be visited. The {@code visitFile} method is invoked for all
2750 * files, including directories, encountered at {@code maxDepth}, unless the
2751 * basic file attributes cannot be read, in which case the {@code
2752 * visitFileFailed} method is invoked.
2753 *
2754 * <p> If a visitor returns a result of {@code null} then {@code
2755 * NullPointerException} is thrown.
2756 *
2757 * <p> When a security manager is installed and it denies access to a file
2758 * (or directory), then it is ignored and the visitor is not invoked for
2759 * that file (or directory).
2760 *
2761 * @param start
2762 * the starting file
2763 * @param options
2764 * options to configure the traversal
2765 * @param maxDepth
2766 * the maximum number of directory levels to visit
2767 * @param visitor
2768 * the file visitor to invoke for each file
2769 *
2770 * @return the starting file
2771 *
2772 * @throws IllegalArgumentException
2773 * if the {@code maxDepth} parameter is negative
2774 * @throws SecurityException
2775 * If the security manager denies access to the starting file.
2776 * In the case of the default provider, the {@link
2777 * SecurityManager#checkRead(String) checkRead} method is invoked
2778 * to check read access to the directory.
2779 * @throws IOException
2780 * if an I/O error is thrown by a visitor method
2781 */
2782 public static Path walkFileTree(Path start,
2783 Set<FileVisitOption> options,
2784 int maxDepth,
2785 FileVisitor<? super Path> visitor)
2786 throws IOException
2787 {
2788 /**
2789 * Create a FileTreeWalker to walk the file tree, invoking the visitor
2790 * for each event.
2791 */
2792 try (FileTreeWalker walker = new FileTreeWalker(options, maxDepth)) {
2793 FileTreeWalker.Event ev = walker.walk(start);
2794 do {
2795 FileVisitResult result;
2796 switch (ev.type()) {
2797 case ENTRY :
2798 IOException ioe = ev.ioeException();
2799 if (ioe == null) {
2800 assert ev.attributes() != null;
2801 result = visitor.visitFile(ev.file(), ev.attributes());
2802 } else {
2803 result = visitor.visitFileFailed(ev.file(), ioe);
2804 }
2805 break;
2806
2807 case START_DIRECTORY :
2808 result = visitor.preVisitDirectory(ev.file(), ev.attributes());
2809
2810 // if SKIP_SIBLINGS and SKIP_SUBTREE is returned then
2811 // there shouldn't be any more events for the current
2812 // directory.
2813 if (result == FileVisitResult.SKIP_SUBTREE ||
2814 result == FileVisitResult.SKIP_SIBLINGS)
2815 walker.pop();
2816 break;
2817
2818 case END_DIRECTORY :
2819 result = visitor.postVisitDirectory(ev.file(), ev.ioeException());
2820
2821 // SKIP_SIBLINGS is a no-op for postVisitDirectory
2822 if (result == FileVisitResult.SKIP_SIBLINGS)
2823 result = FileVisitResult.CONTINUE;
2824 break;
2825
2826 default :
2827 throw new AssertionError("Should not get here");
2828 }
2829
2830 if (Objects.requireNonNull(result) != FileVisitResult.CONTINUE) {
2831 if (result == FileVisitResult.TERMINATE) {
2832 break;
2833 } else if (result == FileVisitResult.SKIP_SIBLINGS) {
2834 walker.skipRemainingSiblings();
2835 }
2836 }
2837 ev = walker.next();
2838 } while (ev != null);
2839 }
2840
2841 return start;
2842 }
2843
2844 /**
2845 * Walks a file tree.
2846 *
2847 * <p> This method works as if invoking it were equivalent to evaluating the
2848 * expression:
2849 * <blockquote><pre>
2850 * walkFileTree(start, EnumSet.noneOf(FileVisitOption.class), Integer.MAX_VALUE, visitor)
2851 * </pre></blockquote>
2852 * In other words, it does not follow symbolic links, and visits all levels
2853 * of the file tree.
2854 *
2855 * @param start
2856 * the starting file
2857 * @param visitor
2858 * the file visitor to invoke for each file
2859 *
2860 * @return the starting file
2861 *
2862 * @throws SecurityException
2863 * If the security manager denies access to the starting file.
2864 * In the case of the default provider, the {@link
2865 * SecurityManager#checkRead(String) checkRead} method is invoked
2866 * to check read access to the directory.
2867 * @throws IOException
2868 * if an I/O error is thrown by a visitor method
2869 */
2870 public static Path walkFileTree(Path start, FileVisitor<? super Path> visitor)
2871 throws IOException
2872 {
2873 return walkFileTree(start,
2874 EnumSet.noneOf(FileVisitOption.class),
2875 Integer.MAX_VALUE,
2876 visitor);
2877 }
2878
2879
2880 // -- Utility methods for simple usages --
2881
2882
2883 /**
2884 * Opens a file for reading, returning a {@code BufferedReader} that may be
2885 * used to read text from the file in an efficient manner. Bytes from the
2886 * file are decoded into characters using the specified charset. Reading
2887 * commences at the beginning of the file.
2888 *
2889 * <p> The {@code Reader} methods that read from the file throw {@code
2890 * IOException} if a malformed or unmappable byte sequence is read.
2891 *
2892 * @param path
2893 * the path to the file
2894 * @param cs
2895 * the charset to use for decoding
2896 *
2897 * @return a new buffered reader, with default buffer size, to read text
2898 * from the file
2899 *
2900 * @throws IOException
2901 * if an I/O error occurs opening the file
2902 * @throws SecurityException
2903 * In the case of the default provider, and a security manager is
2904 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2905 * method is invoked to check read access to the file.
2906 *
2907 * @see #readAllLines
2908 */
2909 public static BufferedReader newBufferedReader(Path path, Charset cs)
2910 throws IOException
2911 {
2912 CharsetDecoder decoder = cs.newDecoder();
2913 Reader reader = new InputStreamReader(newInputStream(path), decoder);
2914 return new BufferedReader(reader);
2915 }
2916
2917 /**
2918 * Opens a file for reading, returning a {@code BufferedReader} to read text
2919 * from the file in an efficient manner. Bytes from the file are decoded into
2920 * characters using the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset
2921 * charset}.
2922 *
2923 * <p> This method works as if invoking it were equivalent to evaluating the
2924 * expression:
2925 * <pre>{@code
2926 * Files.newBufferedReader(path, StandardCharsets.UTF_8)
2927 * }</pre>
2928 *
2929 * @param path
2930 * the path to the file
2931 *
2932 * @return a new buffered reader, with default buffer size, to read text
2933 * from the file
2934 *
2935 * @throws IOException
2936 * if an I/O error occurs opening the file
2937 * @throws SecurityException
2938 * In the case of the default provider, and a security manager is
2939 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2940 * method is invoked to check read access to the file.
2941 *
2942 * @since 1.8
2943 */
2944 public static BufferedReader newBufferedReader(Path path) throws IOException {
2945 return newBufferedReader(path, StandardCharsets.UTF_8);
2946 }
2947
2948 /**
2949 * Opens or creates a file for writing, returning a {@code BufferedWriter}
2950 * that may be used to write text to the file in an efficient manner.
2951 * The {@code options} parameter specifies how the file is created or
2952 * opened. If no options are present then this method works as if the {@link
2953 * StandardOpenOption#CREATE CREATE}, {@link
2954 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
2955 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
2956 * opens the file for writing, creating the file if it doesn't exist, or
2957 * initially truncating an existing {@link #isRegularFile regular-file} to
2958 * a size of {@code 0} if it exists.
2959 *
2960 * <p> The {@code Writer} methods to write text throw {@code IOException}
2961 * if the text cannot be encoded using the specified charset.
2962 *
2963 * @param path
2964 * the path to the file
2965 * @param cs
2966 * the charset to use for encoding
2967 * @param options
2968 * options specifying how the file is opened
2969 *
2970 * @return a new buffered writer, with default buffer size, to write text
2971 * to the file
2972 *
2973 * @throws IllegalArgumentException
2974 * if {@code options} contains an invalid combination of options
2975 * @throws IOException
2976 * if an I/O error occurs opening or creating the file
2977 * @throws UnsupportedOperationException
2978 * if an unsupported option is specified
2979 * @throws SecurityException
2980 * In the case of the default provider, and a security manager is
2981 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2982 * method is invoked to check write access to the file. The {@link
2983 * SecurityManager#checkDelete(String) checkDelete} method is
2984 * invoked to check delete access if the file is opened with the
2985 * {@code DELETE_ON_CLOSE} option.
2986 *
2987 * @see #write(Path,Iterable,Charset,OpenOption[])
2988 */
2989 public static BufferedWriter newBufferedWriter(Path path, Charset cs,
2990 OpenOption... options)
2991 throws IOException
2992 {
2993 CharsetEncoder encoder = cs.newEncoder();
2994 Writer writer = new OutputStreamWriter(newOutputStream(path, options), encoder);
2995 return new BufferedWriter(writer);
2996 }
2997
2998 /**
2999 * Opens or creates a file for writing, returning a {@code BufferedWriter}
3000 * to write text to the file in an efficient manner. The text is encoded
3001 * into bytes for writing using the {@link StandardCharsets#UTF_8 UTF-8}
3002 * {@link Charset charset}.
3003 *
3004 * <p> This method works as if invoking it were equivalent to evaluating the
3005 * expression:
3006 * <pre>{@code
3007 * Files.newBufferedWriter(path, StandardCharsets.UTF_8, options)
3008 * }</pre>
3009 *
3010 * @param path
3011 * the path to the file
3012 * @param options
3013 * options specifying how the file is opened
3014 *
3015 * @return a new buffered writer, with default buffer size, to write text
3016 * to the file
3017 *
3018 * @throws IllegalArgumentException
3019 * if {@code options} contains an invalid combination of options
3020 * @throws IOException
3021 * if an I/O error occurs opening or creating the file
3022 * @throws UnsupportedOperationException
3023 * if an unsupported option is specified
3024 * @throws SecurityException
3025 * In the case of the default provider, and a security manager is
3026 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3027 * method is invoked to check write access to the file. The {@link
3028 * SecurityManager#checkDelete(String) checkDelete} method is
3029 * invoked to check delete access if the file is opened with the
3030 * {@code DELETE_ON_CLOSE} option.
3031 *
3032 * @since 1.8
3033 */
3034 public static BufferedWriter newBufferedWriter(Path path, OpenOption... options)
3035 throws IOException
3036 {
3037 return newBufferedWriter(path, StandardCharsets.UTF_8, options);
3038 }
3039
3040 /**
3041 * Copies all bytes from an input stream to a file. On return, the input
3042 * stream will be at end of stream.
3043 *
3044 * <p> By default, the copy fails if the target file already exists or is a
3045 * symbolic link. If the {@link StandardCopyOption#REPLACE_EXISTING
3046 * REPLACE_EXISTING} option is specified, and the target file already exists,
3047 * then it is replaced if it is not a non-empty directory. If the target
3048 * file exists and is a symbolic link, then the symbolic link is replaced.
3049 * In this release, the {@code REPLACE_EXISTING} option is the only option
3050 * required to be supported by this method. Additional options may be
3051 * supported in future releases.
3052 *
3053 * <p> If an I/O error occurs reading from the input stream or writing to
3054 * the file, then it may do so after the target file has been created and
3055 * after some bytes have been read or written. Consequently the input
3056 * stream may not be at end of stream and may be in an inconsistent state.
3057 * It is strongly recommended that the input stream be promptly closed if an
3058 * I/O error occurs.
3059 *
3060 * <p> This method may block indefinitely reading from the input stream (or
3061 * writing to the file). The behavior for the case that the input stream is
3062 * <i>asynchronously closed</i> or the thread interrupted during the copy is
3063 * highly input stream and file system provider specific and therefore not
3064 * specified.
3065 *
3066 * <p> <b>Usage example</b>: Suppose we want to capture a web page and save
3067 * it to a file:
3068 * <pre>
3069 * Path path = ...
3070 * URI u = URI.create("http://java.sun.com/");
3071 * try (InputStream in = u.toURL().openStream()) {
3072 * Files.copy(in, path);
3073 * }
3074 * </pre>
3075 *
3076 * @param in
3077 * the input stream to read from
3078 * @param target
3079 * the path to the file
3080 * @param options
3081 * options specifying how the copy should be done
3082 *
3083 * @return the number of bytes read or written
3084 *
3085 * @throws IOException
3086 * if an I/O error occurs when reading or writing
3087 * @throws FileAlreadyExistsException
3088 * if the target file exists but cannot be replaced because the
3089 * {@code REPLACE_EXISTING} option is not specified <i>(optional
3090 * specific exception)</i>
3091 * @throws DirectoryNotEmptyException
3092 * the {@code REPLACE_EXISTING} option is specified but the file
3093 * cannot be replaced because it is a non-empty directory
3094 * <i>(optional specific exception)</i> *
3095 * @throws UnsupportedOperationException
3096 * if {@code options} contains a copy option that is not supported
3097 * @throws SecurityException
3098 * In the case of the default provider, and a security manager is
3099 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3100 * method is invoked to check write access to the file. Where the
3101 * {@code REPLACE_EXISTING} option is specified, the security
3102 * manager's {@link SecurityManager#checkDelete(String) checkDelete}
3103 * method is invoked to check that an existing file can be deleted.
3104 */
3105 public static long copy(InputStream in, Path target, CopyOption... options)
3106 throws IOException
3107 {
3108 // ensure not null before opening file
3109 Objects.requireNonNull(in);
3110
3111 // check for REPLACE_EXISTING
3112 boolean replaceExisting = false;
3113 for (CopyOption opt: options) {
3114 if (opt == StandardCopyOption.REPLACE_EXISTING) {
3115 replaceExisting = true;
3116 } else {
3117 if (opt == null) {
3118 throw new NullPointerException("options contains 'null'");
3119 } else {
3120 throw new UnsupportedOperationException(opt + " not supported");
3121 }
3122 }
3123 }
3124
3125 // attempt to delete an existing file
3126 SecurityException se = null;
3127 if (replaceExisting) {
3128 try {
3129 deleteIfExists(target);
3130 } catch (SecurityException x) {
3131 se = x;
3132 }
3133 }
3134
3135 // attempt to create target file. If it fails with
3136 // FileAlreadyExistsException then it may be because the security
3137 // manager prevented us from deleting the file, in which case we just
3138 // throw the SecurityException.
3139 OutputStream ostream;
3140 try {
3141 ostream = newOutputStream(target, StandardOpenOption.CREATE_NEW,
3142 StandardOpenOption.WRITE);
3143 } catch (FileAlreadyExistsException x) {
3144 if (se != null)
3145 throw se;
3146 // someone else won the race and created the file
3147 throw x;
3148 }
3149
3150 // do the copy
3151 try (OutputStream out = ostream) {
3152 return in.transferTo(out);
3153 }
3154 }
3155
3156 /**
3157 * Copies all bytes from a file to an output stream.
3158 *
3159 * <p> If an I/O error occurs reading from the file or writing to the output
3160 * stream, then it may do so after some bytes have been read or written.
3161 * Consequently the output stream may be in an inconsistent state. It is
3162 * strongly recommended that the output stream be promptly closed if an I/O
3163 * error occurs.
3164 *
3165 * <p> This method may block indefinitely writing to the output stream (or
3166 * reading from the file). The behavior for the case that the output stream
3167 * is <i>asynchronously closed</i> or the thread interrupted during the copy
3168 * is highly output stream and file system provider specific and therefore
3169 * not specified.
3170 *
3171 * <p> Note that if the given output stream is {@link java.io.Flushable}
3172 * then its {@link java.io.Flushable#flush flush} method may need to invoked
3173 * after this method completes so as to flush any buffered output.
3174 *
3175 * @param source
3176 * the path to the file
3177 * @param out
3178 * the output stream to write to
3179 *
3180 * @return the number of bytes read or written
3181 *
3182 * @throws IOException
3183 * if an I/O error occurs when reading or writing
3184 * @throws SecurityException
3185 * In the case of the default provider, and a security manager is
3186 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3187 * method is invoked to check read access to the file.
3188 */
3189 public static long copy(Path source, OutputStream out) throws IOException {
3190 // ensure not null before opening file
3191 Objects.requireNonNull(out);
3192
3193 try (InputStream in = newInputStream(source)) {
3194 return in.transferTo(out);
3195 }
3196 }
3197
3198 /**
3199 * The maximum size of array to allocate.
3200 * Some VMs reserve some header words in an array.
3201 * Attempts to allocate larger arrays may result in
3202 * OutOfMemoryError: Requested array size exceeds VM limit
3203 */
3204 private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
3205
3206 private static final jdk.internal.access.JavaLangAccess JLA =
3207 jdk.internal.access.SharedSecrets.getJavaLangAccess();
3208
3209 /**
3210 * Reads all the bytes from an input stream. Uses {@code initialSize} as a hint
3211 * about how many bytes the stream will have.
3212 *
3213 * @param source
3214 * the input stream to read from
3215 * @param initialSize
3216 * the initial size of the byte array to allocate
3217 *
3218 * @return a byte array containing the bytes read from the file
3219 *
3220 * @throws IOException
3221 * if an I/O error occurs reading from the stream
3222 * @throws OutOfMemoryError
3223 * if an array of the required size cannot be allocated
3224 */
3225 private static byte[] read(InputStream source, int initialSize) throws IOException {
3226 int capacity = initialSize;
3227 byte[] buf = new byte[capacity];
3228 int nread = 0;
3229 int n;
3230 for (;;) {
3231 // read to EOF which may read more or less than initialSize (eg: file
3232 // is truncated while we are reading)
3233 while ((n = source.read(buf, nread, capacity - nread)) > 0)
3234 nread += n;
3235
3236 // if last call to source.read() returned -1, we are done
3237 // otherwise, try to read one more byte; if that failed we're done too
3238 if (n < 0 || (n = source.read()) < 0)
3239 break;
3240
3241 // one more byte was read; need to allocate a larger buffer
3242 if (capacity <= MAX_BUFFER_SIZE - capacity) {
3243 capacity = Math.max(capacity << 1, BUFFER_SIZE);
3244 } else {
3245 if (capacity == MAX_BUFFER_SIZE)
3246 throw new OutOfMemoryError("Required array size too large");
3247 capacity = MAX_BUFFER_SIZE;
3248 }
3249 buf = Arrays.copyOf(buf, capacity);
3250 buf[nread++] = (byte)n;
3251 }
3252 return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
3253 }
3254
3255 /**
3256 * Reads all the bytes from a file. The method ensures that the file is
3257 * closed when all bytes have been read or an I/O error, or other runtime
3258 * exception, is thrown.
3259 *
3260 * <p> Note that this method is intended for simple cases where it is
3261 * convenient to read all bytes into a byte array. It is not intended for
3262 * reading in large files.
3263 *
3264 * @param path
3265 * the path to the file
3266 *
3267 * @return a byte array containing the bytes read from the file
3268 *
3269 * @throws IOException
3270 * if an I/O error occurs reading from the stream
3271 * @throws OutOfMemoryError
3272 * if an array of the required size cannot be allocated, for
3273 * example the file is larger that {@code 2GB}
3274 * @throws SecurityException
3275 * In the case of the default provider, and a security manager is
3276 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3277 * method is invoked to check read access to the file.
3278 */
3279 public static byte[] readAllBytes(Path path) throws IOException {
3280 try (SeekableByteChannel sbc = Files.newByteChannel(path);
3281 InputStream in = Channels.newInputStream(sbc)) {
3282 if (sbc instanceof FileChannelImpl)
3283 ((FileChannelImpl) sbc).setUninterruptible();
3284 long size = sbc.size();
3285 if (size > (long) MAX_BUFFER_SIZE)
3286 throw new OutOfMemoryError("Required array size too large");
3287 return read(in, (int)size);
3288 }
3289 }
3290
3291 /**
3292 * Reads all content from a file into a string, decoding from bytes to characters
3293 * using the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
3294 * The method ensures that the file is closed when all content have been read
3295 * or an I/O error, or other runtime exception, is thrown.
3296 *
3297 * <p> This method is equivalent to:
3298 * {@code readString(path, StandardCharsets.UTF_8) }
3299 *
3300 * @param path the path to the file
3301 *
3302 * @return a String containing the content read from the file
3303 *
3304 * @throws IOException
3305 * if an I/O error occurs reading from the file or a malformed or
3306 * unmappable byte sequence is read
3307 * @throws OutOfMemoryError
3308 * if the file is extremely large, for example larger than {@code 2GB}
3309 * @throws SecurityException
3310 * In the case of the default provider, and a security manager is
3311 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3312 * method is invoked to check read access to the file.
3313 *
3314 * @since 11
3315 */
3316 public static String readString(Path path) throws IOException {
3317 return readString(path, StandardCharsets.UTF_8);
3318 }
3319
3320 /**
3321 * Reads all characters from a file into a string, decoding from bytes to characters
3322 * using the specified {@linkplain Charset charset}.
3323 * The method ensures that the file is closed when all content have been read
3324 * or an I/O error, or other runtime exception, is thrown.
3325 *
3326 * <p> This method reads all content including the line separators in the middle
3327 * and/or at the end. The resulting string will contain line separators as they
3328 * appear in the file.
3329 *
3330 * @apiNote
3331 * This method is intended for simple cases where it is appropriate and convenient
3332 * to read the content of a file into a String. It is not intended for reading
3333 * very large files.
3334 *
3335 *
3336 *
3337 * @param path the path to the file
3338 * @param cs the charset to use for decoding
3339 *
3340 * @return a String containing the content read from the file
3341 *
3342 * @throws IOException
3343 * if an I/O error occurs reading from the file or a malformed or
3344 * unmappable byte sequence is read
3345 * @throws OutOfMemoryError
3346 * if the file is extremely large, for example larger than {@code 2GB}
3347 * @throws SecurityException
3348 * In the case of the default provider, and a security manager is
3349 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3350 * method is invoked to check read access to the file.
3351 *
3352 * @since 11
3353 */
3354 public static String readString(Path path, Charset cs) throws IOException {
3355 Objects.requireNonNull(path);
3356 Objects.requireNonNull(cs);
3357
3358 byte[] ba = readAllBytes(path);
3359 return JLA.newStringNoRepl(ba, cs);
3360 }
3361
3362 /**
3363 * Read all lines from a file. This method ensures that the file is
3364 * closed when all bytes have been read or an I/O error, or other runtime
3365 * exception, is thrown. Bytes from the file are decoded into characters
3366 * using the specified charset.
3367 *
3368 * <p> This method recognizes the following as line terminators:
3369 * <ul>
3370 * <li> <code>\u000D</code> followed by <code>\u000A</code>,
3371 * CARRIAGE RETURN followed by LINE FEED </li>
3372 * <li> <code>\u000A</code>, LINE FEED </li>
3373 * <li> <code>\u000D</code>, CARRIAGE RETURN </li>
3374 * </ul>
3375 * <p> Additional Unicode line terminators may be recognized in future
3376 * releases.
3377 *
3378 * <p> Note that this method is intended for simple cases where it is
3379 * convenient to read all lines in a single operation. It is not intended
3380 * for reading in large files.
3381 *
3382 * @param path
3383 * the path to the file
3384 * @param cs
3385 * the charset to use for decoding
3386 *
3387 * @return the lines from the file as a {@code List}; whether the {@code
3388 * List} is modifiable or not is implementation dependent and
3389 * therefore not specified
3390 *
3391 * @throws IOException
3392 * if an I/O error occurs reading from the file or a malformed or
3393 * unmappable byte sequence is read
3394 * @throws SecurityException
3395 * In the case of the default provider, and a security manager is
3396 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3397 * method is invoked to check read access to the file.
3398 *
3399 * @see #newBufferedReader
3400 */
3401 public static List<String> readAllLines(Path path, Charset cs) throws IOException {
3402 try (BufferedReader reader = newBufferedReader(path, cs)) {
3403 List<String> result = new ArrayList<>();
3404 for (;;) {
3405 String line = reader.readLine();
3406 if (line == null)
3407 break;
3408 result.add(line);
3409 }
3410 return result;
3411 }
3412 }
3413
3414 /**
3415 * Read all lines from a file. Bytes from the file are decoded into characters
3416 * using the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
3417 *
3418 * <p> This method works as if invoking it were equivalent to evaluating the
3419 * expression:
3420 * <pre>{@code
3421 * Files.readAllLines(path, StandardCharsets.UTF_8)
3422 * }</pre>
3423 *
3424 * @param path
3425 * the path to the file
3426 *
3427 * @return the lines from the file as a {@code List}; whether the {@code
3428 * List} is modifiable or not is implementation dependent and
3429 * therefore not specified
3430 *
3431 * @throws IOException
3432 * if an I/O error occurs reading from the file or a malformed or
3433 * unmappable byte sequence is read
3434 * @throws SecurityException
3435 * In the case of the default provider, and a security manager is
3436 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3437 * method is invoked to check read access to the file.
3438 *
3439 * @since 1.8
3440 */
3441 public static List<String> readAllLines(Path path) throws IOException {
3442 return readAllLines(path, StandardCharsets.UTF_8);
3443 }
3444
3445 /**
3446 * Writes bytes to a file. The {@code options} parameter specifies how
3447 * the file is created or opened. If no options are present then this method
3448 * works as if the {@link StandardOpenOption#CREATE CREATE}, {@link
3449 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3450 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3451 * opens the file for writing, creating the file if it doesn't exist, or
3452 * initially truncating an existing {@link #isRegularFile regular-file} to
3453 * a size of {@code 0}. All bytes in the byte array are written to the file.
3454 * The method ensures that the file is closed when all bytes have been
3455 * written (or an I/O error or other runtime exception is thrown). If an I/O
3456 * error occurs then it may do so after the file has been created or
3457 * truncated, or after some bytes have been written to the file.
3458 *
3459 * <p> <b>Usage example</b>: By default the method creates a new file or
3460 * overwrites an existing file. Suppose you instead want to append bytes
3461 * to an existing file:
3462 * <pre>
3463 * Path path = ...
3464 * byte[] bytes = ...
3465 * Files.write(path, bytes, StandardOpenOption.APPEND);
3466 * </pre>
3467 *
3468 * @param path
3469 * the path to the file
3470 * @param bytes
3471 * the byte array with the bytes to write
3472 * @param options
3473 * options specifying how the file is opened
3474 *
3475 * @return the path
3476 *
3477 * @throws IllegalArgumentException
3478 * if {@code options} contains an invalid combination of options
3479 * @throws IOException
3480 * if an I/O error occurs writing to or creating the file
3481 * @throws UnsupportedOperationException
3482 * if an unsupported option is specified
3483 * @throws SecurityException
3484 * In the case of the default provider, and a security manager is
3485 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3486 * method is invoked to check write access to the file. The {@link
3487 * SecurityManager#checkDelete(String) checkDelete} method is
3488 * invoked to check delete access if the file is opened with the
3489 * {@code DELETE_ON_CLOSE} option.
3490 */
3491 public static Path write(Path path, byte[] bytes, OpenOption... options)
3492 throws IOException
3493 {
3494 // ensure bytes is not null before opening file
3495 Objects.requireNonNull(bytes);
3496
3497 try (OutputStream out = Files.newOutputStream(path, options)) {
3498 int len = bytes.length;
3499 int rem = len;
3500 while (rem > 0) {
3501 int n = Math.min(rem, BUFFER_SIZE);
3502 out.write(bytes, (len-rem), n);
3503 rem -= n;
3504 }
3505 }
3506 return path;
3507 }
3508
3509 /**
3510 * Write lines of text to a file. Each line is a char sequence and is
3511 * written to the file in sequence with each line terminated by the
3512 * platform's line separator, as defined by the system property {@code
3513 * line.separator}. Characters are encoded into bytes using the specified
3514 * charset.
3515 *
3516 * <p> The {@code options} parameter specifies how the file is created
3517 * or opened. If no options are present then this method works as if the
3518 * {@link StandardOpenOption#CREATE CREATE}, {@link
3519 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3520 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3521 * opens the file for writing, creating the file if it doesn't exist, or
3522 * initially truncating an existing {@link #isRegularFile regular-file} to
3523 * a size of {@code 0}. The method ensures that the file is closed when all
3524 * lines have been written (or an I/O error or other runtime exception is
3525 * thrown). If an I/O error occurs then it may do so after the file has
3526 * been created or truncated, or after some bytes have been written to the
3527 * file.
3528 *
3529 * @param path
3530 * the path to the file
3531 * @param lines
3532 * an object to iterate over the char sequences
3533 * @param cs
3534 * the charset to use for encoding
3535 * @param options
3536 * options specifying how the file is opened
3537 *
3538 * @return the path
3539 *
3540 * @throws IllegalArgumentException
3541 * if {@code options} contains an invalid combination of options
3542 * @throws IOException
3543 * if an I/O error occurs writing to or creating the file, or the
3544 * text cannot be encoded using the specified charset
3545 * @throws UnsupportedOperationException
3546 * if an unsupported option is specified
3547 * @throws SecurityException
3548 * In the case of the default provider, and a security manager is
3549 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3550 * method is invoked to check write access to the file. The {@link
3551 * SecurityManager#checkDelete(String) checkDelete} method is
3552 * invoked to check delete access if the file is opened with the
3553 * {@code DELETE_ON_CLOSE} option.
3554 */
3555 public static Path write(Path path, Iterable<? extends CharSequence> lines,
3556 Charset cs, OpenOption... options)
3557 throws IOException
3558 {
3559 // ensure lines is not null before opening file
3560 Objects.requireNonNull(lines);
3561 CharsetEncoder encoder = cs.newEncoder();
3562 OutputStream out = newOutputStream(path, options);
3563 try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, encoder))) {
3564 for (CharSequence line: lines) {
3565 writer.append(line);
3566 writer.newLine();
3567 }
3568 }
3569 return path;
3570 }
3571
3572 /**
3573 * Write lines of text to a file. Characters are encoded into bytes using
3574 * the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
3575 *
3576 * <p> This method works as if invoking it were equivalent to evaluating the
3577 * expression:
3578 * <pre>{@code
3579 * Files.write(path, lines, StandardCharsets.UTF_8, options);
3580 * }</pre>
3581 *
3582 * @param path
3583 * the path to the file
3584 * @param lines
3585 * an object to iterate over the char sequences
3586 * @param options
3587 * options specifying how the file is opened
3588 *
3589 * @return the path
3590 *
3591 * @throws IllegalArgumentException
3592 * if {@code options} contains an invalid combination of options
3593 * @throws IOException
3594 * if an I/O error occurs writing to or creating the file, or the
3595 * text cannot be encoded as {@code UTF-8}
3596 * @throws UnsupportedOperationException
3597 * if an unsupported option is specified
3598 * @throws SecurityException
3599 * In the case of the default provider, and a security manager is
3600 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3601 * method is invoked to check write access to the file. The {@link
3602 * SecurityManager#checkDelete(String) checkDelete} method is
3603 * invoked to check delete access if the file is opened with the
3604 * {@code DELETE_ON_CLOSE} option.
3605 *
3606 * @since 1.8
3607 */
3608 public static Path write(Path path,
3609 Iterable<? extends CharSequence> lines,
3610 OpenOption... options)
3611 throws IOException
3612 {
3613 return write(path, lines, StandardCharsets.UTF_8, options);
3614 }
3615
3616 /**
3617 * Write a {@linkplain java.lang.CharSequence CharSequence} to a file.
3618 * Characters are encoded into bytes using the
3619 * {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
3620 *
3621 * <p> This method is equivalent to:
3622 * {@code writeString(path, test, StandardCharsets.UTF_8, options) }
3623 *
3624 * @param path
3625 * the path to the file
3626 * @param csq
3627 * the CharSequence to be written
3628 * @param options
3629 * options specifying how the file is opened
3630 *
3631 * @return the path
3632 *
3633 * @throws IllegalArgumentException
3634 * if {@code options} contains an invalid combination of options
3635 * @throws IOException
3636 * if an I/O error occurs writing to or creating the file, or the
3637 * text cannot be encoded using the specified charset
3638 * @throws UnsupportedOperationException
3639 * if an unsupported option is specified
3640 * @throws SecurityException
3641 * In the case of the default provider, and a security manager is
3642 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3643 * method is invoked to check write access to the file. The {@link
3644 * SecurityManager#checkDelete(String) checkDelete} method is
3645 * invoked to check delete access if the file is opened with the
3646 * {@code DELETE_ON_CLOSE} option.
3647 *
3648 * @since 11
3649 */
3650 public static Path writeString(Path path, CharSequence csq, OpenOption... options)
3651 throws IOException
3652 {
3653 return writeString(path, csq, StandardCharsets.UTF_8, options);
3654 }
3655
3656 /**
3657 * Write a {@linkplain java.lang.CharSequence CharSequence} to a file.
3658 * Characters are encoded into bytes using the specified
3659 * {@linkplain java.nio.charset.Charset charset}.
3660 *
3661 * <p> All characters are written as they are, including the line separators in
3662 * the char sequence. No extra characters are added.
3663 *
3664 * <p> The {@code options} parameter specifies how the file is created
3665 * or opened. If no options are present then this method works as if the
3666 * {@link StandardOpenOption#CREATE CREATE}, {@link
3667 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3668 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3669 * opens the file for writing, creating the file if it doesn't exist, or
3670 * initially truncating an existing {@link #isRegularFile regular-file} to
3671 * a size of {@code 0}.
3672 *
3673 *
3674 * @param path
3675 * the path to the file
3676 * @param csq
3677 * the CharSequence to be written
3678 * @param cs
3679 * the charset to use for encoding
3680 * @param options
3681 * options specifying how the file is opened
3682 *
3683 * @return the path
3684 *
3685 * @throws IllegalArgumentException
3686 * if {@code options} contains an invalid combination of options
3687 * @throws IOException
3688 * if an I/O error occurs writing to or creating the file, or the
3689 * text cannot be encoded using the specified charset
3690 * @throws UnsupportedOperationException
3691 * if an unsupported option is specified
3692 * @throws SecurityException
3693 * In the case of the default provider, and a security manager is
3694 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3695 * method is invoked to check write access to the file. The {@link
3696 * SecurityManager#checkDelete(String) checkDelete} method is
3697 * invoked to check delete access if the file is opened with the
3698 * {@code DELETE_ON_CLOSE} option.
3699 *
3700 * @since 11
3701 */
3702 public static Path writeString(Path path, CharSequence csq, Charset cs, OpenOption... options)
3703 throws IOException
3704 {
3705 // ensure the text is not null before opening file
3706 Objects.requireNonNull(path);
3707 Objects.requireNonNull(csq);
3708 Objects.requireNonNull(cs);
3709
3710 byte[] bytes = JLA.getBytesNoRepl(String.valueOf(csq), cs);
3711 write(path, bytes, options);
3712
3713 return path;
3714 }
3715
3716 // -- Stream APIs --
3717
3718 /**
3719 * Return a lazily populated {@code Stream}, the elements of
3720 * which are the entries in the directory. The listing is not recursive.
3721 *
3722 * <p> The elements of the stream are {@link Path} objects that are
3723 * obtained as if by {@link Path#resolve(Path) resolving} the name of the
3724 * directory entry against {@code dir}. Some file systems maintain special
3725 * links to the directory itself and the directory's parent directory.
3726 * Entries representing these links are not included.
3727 *
3728 * <p> The stream is <i>weakly consistent</i>. It is thread safe but does
3729 * not freeze the directory while iterating, so it may (or may not)
3730 * reflect updates to the directory that occur after returning from this
3731 * method.
3732 *
3733 * <p> The returned stream contains a reference to an open directory.
3734 * The directory is closed by closing the stream.
3735 *
3736 * <p> Operating on a closed stream behaves as if the end of stream
3737 * has been reached. Due to read-ahead, one or more elements may be
3738 * returned after the stream has been closed.
3739 *
3740 * <p> If an {@link IOException} is thrown when accessing the directory
3741 * after this method has returned, it is wrapped in an {@link
3742 * UncheckedIOException} which will be thrown from the method that caused
3743 * the access to take place.
3744 *
3745 * @apiNote
3746 * This method must be used within a try-with-resources statement or similar
3747 * control structure to ensure that the stream's open directory is closed
3748 * promptly after the stream's operations have completed.
3749 *
3750 * @param dir The path to the directory
3751 *
3752 * @return The {@code Stream} describing the content of the
3753 * directory
3754 *
3755 * @throws NotDirectoryException
3756 * if the file could not otherwise be opened because it is not
3757 * a directory <i>(optional specific exception)</i>
3758 * @throws IOException
3759 * if an I/O error occurs when opening the directory
3760 * @throws SecurityException
3761 * In the case of the default provider, and a security manager is
3762 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3763 * method is invoked to check read access to the directory.
3764 *
3765 * @see #newDirectoryStream(Path)
3766 * @since 1.8
3767 */
3768 public static Stream<Path> list(Path dir) throws IOException {
3769 DirectoryStream<Path> ds = Files.newDirectoryStream(dir);
3770 try {
3771 final Iterator<Path> delegate = ds.iterator();
3772
3773 // Re-wrap DirectoryIteratorException to UncheckedIOException
3774 Iterator<Path> iterator = new Iterator<>() {
3775 @Override
3776 public boolean hasNext() {
3777 try {
3778 return delegate.hasNext();
3779 } catch (DirectoryIteratorException e) {
3780 throw new UncheckedIOException(e.getCause());
3781 }
3782 }
3783 @Override
3784 public Path next() {
3785 try {
3786 return delegate.next();
3787 } catch (DirectoryIteratorException e) {
3788 throw new UncheckedIOException(e.getCause());
3789 }
3790 }
3791 };
3792
3793 Spliterator<Path> spliterator =
3794 Spliterators.spliteratorUnknownSize(iterator, Spliterator.DISTINCT);
3795 return StreamSupport.stream(spliterator, false)
3796 .onClose(asUncheckedRunnable(ds));
3797 } catch (Error|RuntimeException e) {
3798 try {
3799 ds.close();
3800 } catch (IOException ex) {
3801 try {
3802 e.addSuppressed(ex);
3803 } catch (Throwable ignore) {}
3804 }
3805 throw e;
3806 }
3807 }
3808
3809 /**
3810 * Return a {@code Stream} that is lazily populated with {@code
3811 * Path} by walking the file tree rooted at a given starting file. The
3812 * file tree is traversed <em>depth-first</em>, the elements in the stream
3813 * are {@link Path} objects that are obtained as if by {@link
3814 * Path#resolve(Path) resolving} the relative path against {@code start}.
3815 *
3816 * <p> The {@code stream} walks the file tree as elements are consumed.
3817 * The {@code Stream} returned is guaranteed to have at least one
3818 * element, the starting file itself. For each file visited, the stream
3819 * attempts to read its {@link BasicFileAttributes}. If the file is a
3820 * directory and can be opened successfully, entries in the directory, and
3821 * their <em>descendants</em> will follow the directory in the stream as
3822 * they are encountered. When all entries have been visited, then the
3823 * directory is closed. The file tree walk then continues at the next
3824 * <em>sibling</em> of the directory.
3825 *
3826 * <p> The stream is <i>weakly consistent</i>. It does not freeze the
3827 * file tree while iterating, so it may (or may not) reflect updates to
3828 * the file tree that occur after returned from this method.
3829 *
3830 * <p> By default, symbolic links are not automatically followed by this
3831 * method. If the {@code options} parameter contains the {@link
3832 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then symbolic links are
3833 * followed. When following links, and the attributes of the target cannot
3834 * be read, then this method attempts to get the {@code BasicFileAttributes}
3835 * of the link.
3836 *
3837 * <p> If the {@code options} parameter contains the {@link
3838 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then the stream keeps
3839 * track of directories visited so that cycles can be detected. A cycle
3840 * arises when there is an entry in a directory that is an ancestor of the
3841 * directory. Cycle detection is done by recording the {@link
3842 * java.nio.file.attribute.BasicFileAttributes#fileKey file-key} of directories,
3843 * or if file keys are not available, by invoking the {@link #isSameFile
3844 * isSameFile} method to test if a directory is the same file as an
3845 * ancestor. When a cycle is detected it is treated as an I/O error with
3846 * an instance of {@link FileSystemLoopException}.
3847 *
3848 * <p> The {@code maxDepth} parameter is the maximum number of levels of
3849 * directories to visit. A value of {@code 0} means that only the starting
3850 * file is visited, unless denied by the security manager. A value of
3851 * {@link Integer#MAX_VALUE MAX_VALUE} may be used to indicate that all
3852 * levels should be visited.
3853 *
3854 * <p> When a security manager is installed and it denies access to a file
3855 * (or directory), then it is ignored and not included in the stream.
3856 *
3857 * <p> The returned stream contains references to one or more open directories.
3858 * The directories are closed by closing the stream.
3859 *
3860 * <p> If an {@link IOException} is thrown when accessing the directory
3861 * after this method has returned, it is wrapped in an {@link
3862 * UncheckedIOException} which will be thrown from the method that caused
3863 * the access to take place.
3864 *
3865 * @apiNote
3866 * This method must be used within a try-with-resources statement or similar
3867 * control structure to ensure that the stream's open directories are closed
3868 * promptly after the stream's operations have completed.
3869 *
3870 * @param start
3871 * the starting file
3872 * @param maxDepth
3873 * the maximum number of directory levels to visit
3874 * @param options
3875 * options to configure the traversal
3876 *
3877 * @return the {@link Stream} of {@link Path}
3878 *
3879 * @throws IllegalArgumentException
3880 * if the {@code maxDepth} parameter is negative
3881 * @throws SecurityException
3882 * If the security manager denies access to the starting file.
3883 * In the case of the default provider, the {@link
3884 * SecurityManager#checkRead(String) checkRead} method is invoked
3885 * to check read access to the directory.
3886 * @throws IOException
3887 * if an I/O error is thrown when accessing the starting file.
3888 * @since 1.8
3889 */
3890 public static Stream<Path> walk(Path start,
3891 int maxDepth,
3892 FileVisitOption... options)
3893 throws IOException
3894 {
3895 FileTreeIterator iterator = new FileTreeIterator(start, maxDepth, options);
3896 try {
3897 Spliterator<FileTreeWalker.Event> spliterator =
3898 Spliterators.spliteratorUnknownSize(iterator, Spliterator.DISTINCT);
3899 return StreamSupport.stream(spliterator, false)
3900 .onClose(iterator::close)
3901 .map(entry -> entry.file());
3902 } catch (Error|RuntimeException e) {
3903 iterator.close();
3904 throw e;
3905 }
3906 }
3907
3908 /**
3909 * Return a {@code Stream} that is lazily populated with {@code
3910 * Path} by walking the file tree rooted at a given starting file. The
3911 * file tree is traversed <em>depth-first</em>, the elements in the stream
3912 * are {@link Path} objects that are obtained as if by {@link
3913 * Path#resolve(Path) resolving} the relative path against {@code start}.
3914 *
3915 * <p> This method works as if invoking it were equivalent to evaluating the
3916 * expression:
3917 * <blockquote><pre>
3918 * walk(start, Integer.MAX_VALUE, options)
3919 * </pre></blockquote>
3920 * In other words, it visits all levels of the file tree.
3921 *
3922 * <p> The returned stream contains references to one or more open directories.
3923 * The directories are closed by closing the stream.
3924 *
3925 * @apiNote
3926 * This method must be used within a try-with-resources statement or similar
3927 * control structure to ensure that the stream's open directories are closed
3928 * promptly after the stream's operations have completed.
3929 *
3930 * @param start
3931 * the starting file
3932 * @param options
3933 * options to configure the traversal
3934 *
3935 * @return the {@link Stream} of {@link Path}
3936 *
3937 * @throws SecurityException
3938 * If the security manager denies access to the starting file.
3939 * In the case of the default provider, the {@link
3940 * SecurityManager#checkRead(String) checkRead} method is invoked
3941 * to check read access to the directory.
3942 * @throws IOException
3943 * if an I/O error is thrown when accessing the starting file.
3944 *
3945 * @see #walk(Path, int, FileVisitOption...)
3946 * @since 1.8
3947 */
3948 public static Stream<Path> walk(Path start, FileVisitOption... options) throws IOException {
3949 return walk(start, Integer.MAX_VALUE, options);
3950 }
3951
3952 /**
3953 * Return a {@code Stream} that is lazily populated with {@code
3954 * Path} by searching for files in a file tree rooted at a given starting
3955 * file.
3956 *
3957 * <p> This method walks the file tree in exactly the manner specified by
3958 * the {@link #walk walk} method. For each file encountered, the given
3959 * {@link BiPredicate} is invoked with its {@link Path} and {@link
3960 * BasicFileAttributes}. The {@code Path} object is obtained as if by
3961 * {@link Path#resolve(Path) resolving} the relative path against {@code
3962 * start} and is only included in the returned {@link Stream} if
3963 * the {@code BiPredicate} returns true. Compare to calling {@link
3964 * java.util.stream.Stream#filter filter} on the {@code Stream}
3965 * returned by {@code walk} method, this method may be more efficient by
3966 * avoiding redundant retrieval of the {@code BasicFileAttributes}.
3967 *
3968 * <p> The returned stream contains references to one or more open directories.
3969 * The directories are closed by closing the stream.
3970 *
3971 * <p> If an {@link IOException} is thrown when accessing the directory
3972 * after returned from this method, it is wrapped in an {@link
3973 * UncheckedIOException} which will be thrown from the method that caused
3974 * the access to take place.
3975 *
3976 * @apiNote
3977 * This method must be used within a try-with-resources statement or similar
3978 * control structure to ensure that the stream's open directories are closed
3979 * promptly after the stream's operations have completed.
3980 *
3981 * @param start
3982 * the starting file
3983 * @param maxDepth
3984 * the maximum number of directory levels to search
3985 * @param matcher
3986 * the function used to decide whether a file should be included
3987 * in the returned stream
3988 * @param options
3989 * options to configure the traversal
3990 *
3991 * @return the {@link Stream} of {@link Path}
3992 *
3993 * @throws IllegalArgumentException
3994 * if the {@code maxDepth} parameter is negative
3995 * @throws SecurityException
3996 * If the security manager denies access to the starting file.
3997 * In the case of the default provider, the {@link
3998 * SecurityManager#checkRead(String) checkRead} method is invoked
3999 * to check read access to the directory.
4000 * @throws IOException
4001 * if an I/O error is thrown when accessing the starting file.
4002 *
4003 * @see #walk(Path, int, FileVisitOption...)
4004 * @since 1.8
4005 */
4006 public static Stream<Path> find(Path start,
4007 int maxDepth,
4008 BiPredicate<Path, BasicFileAttributes> matcher,
4009 FileVisitOption... options)
4010 throws IOException
4011 {
4012 FileTreeIterator iterator = new FileTreeIterator(start, maxDepth, options);
4013 try {
4014 Spliterator<FileTreeWalker.Event> spliterator =
4015 Spliterators.spliteratorUnknownSize(iterator, Spliterator.DISTINCT);
4016 return StreamSupport.stream(spliterator, false)
4017 .onClose(iterator::close)
4018 .filter(entry -> matcher.test(entry.file(), entry.attributes()))
4019 .map(entry -> entry.file());
4020 } catch (Error|RuntimeException e) {
4021 iterator.close();
4022 throw e;
4023 }
4024 }
4025
4026
4027 /**
4028 * Read all lines from a file as a {@code Stream}. Unlike {@link
4029 * #readAllLines(Path, Charset) readAllLines}, this method does not read
4030 * all lines into a {@code List}, but instead populates lazily as the stream
4031 * is consumed.
4032 *
4033 * <p> Bytes from the file are decoded into characters using the specified
4034 * charset and the same line terminators as specified by {@code
4035 * readAllLines} are supported.
4036 *
4037 * <p> The returned stream contains a reference to an open file. The file
4038 * is closed by closing the stream.
4039 *
4040 * <p> The file contents should not be modified during the execution of the
4041 * terminal stream operation. Otherwise, the result of the terminal stream
4042 * operation is undefined.
4043 *
4044 * <p> After this method returns, then any subsequent I/O exception that
4045 * occurs while reading from the file or when a malformed or unmappable byte
4046 * sequence is read, is wrapped in an {@link UncheckedIOException} that will
4047 * be thrown from the
4048 * {@link java.util.stream.Stream} method that caused the read to take
4049 * place. In case an {@code IOException} is thrown when closing the file,
4050 * it is also wrapped as an {@code UncheckedIOException}.
4051 *
4052 * @apiNote
4053 * This method must be used within a try-with-resources statement or similar
4054 * control structure to ensure that the stream's open file is closed promptly
4055 * after the stream's operations have completed.
4056 *
4057 * @implNote
4058 * This implementation supports good parallel stream performance for the
4059 * standard charsets {@link StandardCharsets#UTF_8 UTF-8},
4060 * {@link StandardCharsets#US_ASCII US-ASCII} and
4061 * {@link StandardCharsets#ISO_8859_1 ISO-8859-1}. Such
4062 * <em>line-optimal</em> charsets have the property that the encoded bytes
4063 * of a line feed ('\n') or a carriage return ('\r') are efficiently
4064 * identifiable from other encoded characters when randomly accessing the
4065 * bytes of the file.
4066 *
4067 * <p> For non-<em>line-optimal</em> charsets the stream source's
4068 * spliterator has poor splitting properties, similar to that of a
4069 * spliterator associated with an iterator or that associated with a stream
4070 * returned from {@link BufferedReader#lines()}. Poor splitting properties
4071 * can result in poor parallel stream performance.
4072 *
4073 * <p> For <em>line-optimal</em> charsets the stream source's spliterator
4074 * has good splitting properties, assuming the file contains a regular
4075 * sequence of lines. Good splitting properties can result in good parallel
4076 * stream performance. The spliterator for a <em>line-optimal</em> charset
4077 * takes advantage of the charset properties (a line feed or a carriage
4078 * return being efficient identifiable) such that when splitting it can
4079 * approximately divide the number of covered lines in half.
4080 *
4081 * @param path
4082 * the path to the file
4083 * @param cs
4084 * the charset to use for decoding
4085 *
4086 * @return the lines from the file as a {@code Stream}
4087 *
4088 * @throws IOException
4089 * if an I/O error occurs opening the file
4090 * @throws SecurityException
4091 * In the case of the default provider, and a security manager is
4092 * installed, the {@link SecurityManager#checkRead(String) checkRead}
4093 * method is invoked to check read access to the file.
4094 *
4095 * @see #readAllLines(Path, Charset)
4096 * @see #newBufferedReader(Path, Charset)
4097 * @see java.io.BufferedReader#lines()
4098 * @since 1.8
4099 */
4100 public static Stream<String> lines(Path path, Charset cs) throws IOException {
4101 // Use the good splitting spliterator if:
4102 // 1) the path is associated with the default file system;
4103 // 2) the character set is supported; and
4104 // 3) the file size is such that all bytes can be indexed by int values
4105 // (this limitation is imposed by ByteBuffer)
4106 if (path.getFileSystem() == FileSystems.getDefault() &&
4107 FileChannelLinesSpliterator.SUPPORTED_CHARSET_NAMES.contains(cs.name())) {
4108 FileChannel fc = FileChannel.open(path, StandardOpenOption.READ);
4109
4110 Stream<String> fcls = createFileChannelLinesStream(fc, cs);
4111 if (fcls != null) {
4112 return fcls;
4113 }
4114 fc.close();
4115 }
4116
4117 return createBufferedReaderLinesStream(Files.newBufferedReader(path, cs));
4118 }
4119
4120 private static Stream<String> createFileChannelLinesStream(FileChannel fc, Charset cs) throws IOException {
4121 try {
4122 // Obtaining the size from the FileChannel is much faster
4123 // than obtaining using path.toFile().length()
4124 long length = fc.size();
4125 // FileChannel.size() may in certain circumstances return zero
4126 // for a non-zero length file so disallow this case.
4127 if (length > 0 && length <= Integer.MAX_VALUE) {
4128 Spliterator<String> s = new FileChannelLinesSpliterator(fc, cs, 0, (int) length);
4129 return StreamSupport.stream(s, false)
4130 .onClose(Files.asUncheckedRunnable(fc));
4131 }
4132 } catch (Error|RuntimeException|IOException e) {
4133 try {
4134 fc.close();
4135 } catch (IOException ex) {
4136 try {
4137 e.addSuppressed(ex);
4138 } catch (Throwable ignore) {
4139 }
4140 }
4141 throw e;
4142 }
4143 return null;
4144 }
4145
4146 private static Stream<String> createBufferedReaderLinesStream(BufferedReader br) {
4147 try {
4148 return br.lines().onClose(asUncheckedRunnable(br));
4149 } catch (Error|RuntimeException e) {
4150 try {
4151 br.close();
4152 } catch (IOException ex) {
4153 try {
4154 e.addSuppressed(ex);
4155 } catch (Throwable ignore) {
4156 }
4157 }
4158 throw e;
4159 }
4160 }
4161
4162 /**
4163 * Read all lines from a file as a {@code Stream}. Bytes from the file are
4164 * decoded into characters using the {@link StandardCharsets#UTF_8 UTF-8}
4165 * {@link Charset charset}.
4166 *
4167 * <p> The returned stream contains a reference to an open file. The file
4168 * is closed by closing the stream.
4169 *
4170 * <p> The file contents should not be modified during the execution of the
4171 * terminal stream operation. Otherwise, the result of the terminal stream
4172 * operation is undefined.
4173 *
4174 * <p> This method works as if invoking it were equivalent to evaluating the
4175 * expression:
4176 * <pre>{@code
4177 * Files.lines(path, StandardCharsets.UTF_8)
4178 * }</pre>
4179 *
4180 * @apiNote
4181 * This method must be used within a try-with-resources statement or similar
4182 * control structure to ensure that the stream's open file is closed promptly
4183 * after the stream's operations have completed.
4184 *
4185 * @param path
4186 * the path to the file
4187 *
4188 * @return the lines from the file as a {@code Stream}
4189 *
4190 * @throws IOException
4191 * if an I/O error occurs opening the file
4192 * @throws SecurityException
4193 * In the case of the default provider, and a security manager is
4194 * installed, the {@link SecurityManager#checkRead(String) checkRead}
4195 * method is invoked to check read access to the file.
4196 *
4197 * @since 1.8
4198 */
4199 public static Stream<String> lines(Path path) throws IOException {
4200 return lines(path, StandardCharsets.UTF_8);
4201 }
4202 }