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.fs.AbstractFileSystemProvider;
81
82 /**
83 * This class consists exclusively of static methods that operate on files,
84 * directories, or other types of files.
85 *
86 * <p> In most cases, the methods defined here will delegate to the associated
87 * file system provider to perform the file operations.
88 *
89 * @since 1.7
90 */
91
92 public final class Files {
93 private Files() { }
94
95 /**
96 * Returns the {@code FileSystemProvider} to delegate to.
97 */
98 private static FileSystemProvider provider(Path path) {
99 return path.getFileSystem().provider();
100 }
101
102 /**
103 * Convert a Closeable to a Runnable by converting checked IOException
104 * to UncheckedIOException
105 */
106 private static Runnable asUncheckedRunnable(Closeable c) {
107 return () -> {
108 try {
109 c.close();
110 } catch (IOException e) {
111 throw new UncheckedIOException(e);
112 }
113 };
114 }
115
116 // -- File contents --
117
118 /**
119 * Opens a file, returning an input stream to read from the file. The stream
120 * will not be buffered, and is not required to support the {@link
121 * InputStream#mark mark} or {@link InputStream#reset reset} methods. The
122 * stream will be safe for access by multiple concurrent threads. Reading
123 * commences at the beginning of the file. Whether the returned stream is
124 * <i>asynchronously closeable</i> and/or <i>interruptible</i> is highly
125 * file system provider specific and therefore not specified.
126 *
127 * <p> The {@code options} parameter determines how the file is opened.
128 * If no options are present then it is equivalent to opening the file with
129 * the {@link StandardOpenOption#READ READ} option. In addition to the {@code
130 * READ} option, an implementation may also support additional implementation
131 * specific options.
132 *
133 * @param path
134 * the path to the file to open
135 * @param options
136 * options specifying how the file is opened
137 *
138 * @return a new input stream
139 *
140 * @throws IllegalArgumentException
141 * if an invalid combination of options is specified
142 * @throws UnsupportedOperationException
143 * if an unsupported option is specified
144 * @throws IOException
145 * if an I/O error occurs
146 * @throws SecurityException
147 * In the case of the default provider, and a security manager is
148 * installed, the {@link SecurityManager#checkRead(String) checkRead}
149 * method is invoked to check read access to the file.
150 */
151 public static InputStream newInputStream(Path path, OpenOption... options)
152 throws IOException
153 {
154 return provider(path).newInputStream(path, options);
155 }
156
157 /**
158 * Opens or creates a file, returning an output stream that may be used to
159 * write bytes to the file. The resulting stream will not be buffered. The
160 * stream will be safe for access by multiple concurrent threads. Whether
161 * the returned stream is <i>asynchronously closeable</i> and/or
162 * <i>interruptible</i> is highly file system provider specific and
163 * therefore not specified.
164 *
165 * <p> This method opens or creates a file in exactly the manner specified
166 * by the {@link #newByteChannel(Path,Set,FileAttribute[]) newByteChannel}
167 * method with the exception that the {@link StandardOpenOption#READ READ}
168 * option may not be present in the array of options. If no options are
169 * present then this method works as if the {@link StandardOpenOption#CREATE
170 * CREATE}, {@link StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING},
171 * and {@link StandardOpenOption#WRITE WRITE} options are present. In other
172 * words, it opens the file for writing, creating the file if it doesn't
173 * exist, or initially truncating an existing {@link #isRegularFile
174 * regular-file} to a size of {@code 0} if it exists.
175 *
176 * <p> <b>Usage Examples:</b>
177 * <pre>
178 * Path path = ...
179 *
180 * // truncate and overwrite an existing file, or create the file if
181 * // it doesn't initially exist
182 * OutputStream out = Files.newOutputStream(path);
183 *
184 * // append to an existing file, fail if the file does not exist
185 * out = Files.newOutputStream(path, APPEND);
186 *
187 * // append to an existing file, create file if it doesn't initially exist
188 * out = Files.newOutputStream(path, CREATE, APPEND);
189 *
190 * // always create new file, failing if it already exists
191 * out = Files.newOutputStream(path, CREATE_NEW);
192 * </pre>
193 *
194 * @param path
195 * the path to the file to open or create
196 * @param options
197 * options specifying how the file is opened
198 *
199 * @return a new output stream
200 *
201 * @throws IllegalArgumentException
202 * if {@code options} contains an invalid combination of options
203 * @throws UnsupportedOperationException
204 * if an unsupported option is specified
205 * @throws IOException
206 * if an I/O error occurs
207 * @throws SecurityException
208 * In the case of the default provider, and a security manager is
209 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
210 * method is invoked to check write access to the file. The {@link
211 * SecurityManager#checkDelete(String) checkDelete} method is
212 * invoked to check delete access if the file is opened with the
213 * {@code DELETE_ON_CLOSE} option.
214 */
215 public static OutputStream newOutputStream(Path path, OpenOption... options)
216 throws IOException
217 {
218 return provider(path).newOutputStream(path, options);
219 }
220
221 /**
222 * Opens or creates a file, returning a seekable byte channel to access the
223 * file.
224 *
225 * <p> The {@code options} parameter determines how the file is opened.
226 * The {@link StandardOpenOption#READ READ} and {@link
227 * StandardOpenOption#WRITE WRITE} options determine if the file should be
228 * opened for reading and/or writing. If neither option (or the {@link
229 * StandardOpenOption#APPEND APPEND} option) is present then the file is
230 * opened for reading. By default reading or writing commence at the
231 * beginning of the file.
232 *
233 * <p> In the addition to {@code READ} and {@code WRITE}, the following
234 * options may be present:
235 *
236 * <table class="striped">
237 * <caption style="display:none">Options</caption>
238 * <thead>
239 * <tr> <th scope="col">Option</th> <th scope="col">Description</th> </tr>
240 * </thead>
241 * <tbody>
242 * <tr>
243 * <th scope="row"> {@link StandardOpenOption#APPEND APPEND} </th>
244 * <td> If this option is present then the file is opened for writing and
245 * each invocation of the channel's {@code write} method first advances
246 * the position to the end of the file and then writes the requested
247 * data. Whether the advancement of the position and the writing of the
248 * data are done in a single atomic operation is system-dependent and
249 * therefore unspecified. This option may not be used in conjunction
250 * with the {@code READ} or {@code TRUNCATE_EXISTING} options. </td>
251 * </tr>
252 * <tr>
253 * <th scope="row"> {@link StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING} </th>
254 * <td> If this option is present then the existing file is truncated to
255 * a size of 0 bytes. This option is ignored when the file is opened only
256 * for reading. </td>
257 * </tr>
258 * <tr>
259 * <th scope="row"> {@link StandardOpenOption#CREATE_NEW CREATE_NEW} </th>
260 * <td> If this option is present then a new file is created, failing if
261 * the file already exists or is a symbolic link. When creating a file the
262 * check for the existence of the file and the creation of the file if it
263 * does not exist is atomic with respect to other file system operations.
264 * This option is ignored when the file is opened only for reading. </td>
265 * </tr>
266 * <tr>
267 * <th scope="row" > {@link StandardOpenOption#CREATE CREATE} </th>
268 * <td> If this option is present then an existing file is opened if it
269 * exists, otherwise a new file is created. This option is ignored if the
270 * {@code CREATE_NEW} option is also present or the file is opened only
271 * for reading. </td>
272 * </tr>
273 * <tr>
274 * <th scope="row" > {@link StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE} </th>
275 * <td> When this option is present then the implementation makes a
276 * <em>best effort</em> attempt to delete the file when closed by the
277 * {@link SeekableByteChannel#close close} method. If the {@code close}
278 * method is not invoked then a <em>best effort</em> attempt is made to
279 * delete the file when the Java virtual machine terminates. </td>
280 * </tr>
281 * <tr>
282 * <th scope="row">{@link StandardOpenOption#SPARSE SPARSE} </th>
283 * <td> When creating a new file this option is a <em>hint</em> that the
284 * new file will be sparse. This option is ignored when not creating
285 * a new file. </td>
286 * </tr>
287 * <tr>
288 * <th scope="row"> {@link StandardOpenOption#SYNC SYNC} </th>
289 * <td> Requires that every update to the file's content or metadata be
290 * written synchronously to the underlying storage device. (see <a
291 * href="package-summary.html#integrity"> Synchronized I/O file
292 * integrity</a>). </td>
293 * </tr>
294 * <tr>
295 * <th scope="row"> {@link StandardOpenOption#DSYNC DSYNC} </th>
296 * <td> Requires that every update to the file's content be written
297 * synchronously to the underlying storage device. (see <a
298 * href="package-summary.html#integrity"> Synchronized I/O file
299 * integrity</a>). </td>
300 * </tr>
301 * </tbody>
302 * </table>
303 *
304 * <p> An implementation may also support additional implementation specific
305 * options.
306 *
307 * <p> The {@code attrs} parameter is optional {@link FileAttribute
308 * file-attributes} to set atomically when a new file is created.
309 *
310 * <p> In the case of the default provider, the returned seekable byte channel
311 * is a {@link java.nio.channels.FileChannel}.
312 *
313 * <p> <b>Usage Examples:</b>
314 * <pre>{@code
315 * Path path = ...
316 *
317 * // open file for reading
318 * ReadableByteChannel rbc = Files.newByteChannel(path, EnumSet.of(READ)));
319 *
320 * // open file for writing to the end of an existing file, creating
321 * // the file if it doesn't already exist
322 * WritableByteChannel wbc = Files.newByteChannel(path, EnumSet.of(CREATE,APPEND));
323 *
324 * // create file with initial permissions, opening it for both reading and writing
325 * FileAttribute<Set<PosixFilePermission>> perms = ...
326 * SeekableByteChannel sbc =
327 * Files.newByteChannel(path, EnumSet.of(CREATE_NEW,READ,WRITE), perms);
328 * }</pre>
329 *
330 * @param path
331 * the path to the file to open or create
332 * @param options
333 * options specifying how the file is opened
334 * @param attrs
335 * an optional list of file attributes to set atomically when
336 * creating the file
337 *
338 * @return a new seekable byte channel
339 *
340 * @throws IllegalArgumentException
341 * if the set contains an invalid combination of options
342 * @throws UnsupportedOperationException
343 * if an unsupported open option is specified or the array contains
344 * attributes that cannot be set atomically when creating the file
345 * @throws FileAlreadyExistsException
346 * if a file of that name already exists and the {@link
347 * StandardOpenOption#CREATE_NEW CREATE_NEW} option is specified
348 * <i>(optional specific exception)</i>
349 * @throws IOException
350 * if an I/O error occurs
351 * @throws SecurityException
352 * In the case of the default provider, and a security manager is
353 * installed, the {@link SecurityManager#checkRead(String) checkRead}
354 * method is invoked to check read access to the path if the file is
355 * opened for reading. The {@link SecurityManager#checkWrite(String)
356 * checkWrite} method is invoked to check write access to the path
357 * if the file is opened for writing. The {@link
358 * SecurityManager#checkDelete(String) checkDelete} method is
359 * invoked to check delete access if the file is opened with the
360 * {@code DELETE_ON_CLOSE} option.
361 *
362 * @see java.nio.channels.FileChannel#open(Path,Set,FileAttribute[])
363 */
364 public static SeekableByteChannel newByteChannel(Path path,
365 Set<? extends OpenOption> options,
366 FileAttribute<?>... attrs)
367 throws IOException
368 {
369 return provider(path).newByteChannel(path, options, attrs);
370 }
371
372 /**
373 * Opens or creates a file, returning a seekable byte channel to access the
374 * file.
375 *
376 * <p> This method opens or creates a file in exactly the manner specified
377 * by the {@link #newByteChannel(Path,Set,FileAttribute[]) newByteChannel}
378 * method.
379 *
380 * @param path
381 * the path to the file to open or create
382 * @param options
383 * options specifying how the file is opened
384 *
385 * @return a new seekable byte channel
386 *
387 * @throws IllegalArgumentException
388 * if the set contains an invalid combination of options
389 * @throws UnsupportedOperationException
390 * if an unsupported open option is specified
391 * @throws FileAlreadyExistsException
392 * if a file of that name already exists and the {@link
393 * StandardOpenOption#CREATE_NEW CREATE_NEW} option is specified
394 * <i>(optional specific exception)</i>
395 * @throws IOException
396 * if an I/O error occurs
397 * @throws SecurityException
398 * In the case of the default provider, and a security manager is
399 * installed, the {@link SecurityManager#checkRead(String) checkRead}
400 * method is invoked to check read access to the path if the file is
401 * opened for reading. The {@link SecurityManager#checkWrite(String)
402 * checkWrite} method is invoked to check write access to the path
403 * if the file is opened for writing. The {@link
404 * SecurityManager#checkDelete(String) checkDelete} method is
405 * invoked to check delete access if the file is opened with the
406 * {@code DELETE_ON_CLOSE} option.
407 *
408 * @see java.nio.channels.FileChannel#open(Path,OpenOption[])
409 */
410 public static SeekableByteChannel newByteChannel(Path path, OpenOption... options)
411 throws IOException
412 {
413 Set<OpenOption> set = new HashSet<>(options.length);
414 Collections.addAll(set, options);
415 return newByteChannel(path, set);
416 }
417
418 // -- Directories --
419
420 private static class AcceptAllFilter
421 implements DirectoryStream.Filter<Path>
422 {
423 private AcceptAllFilter() { }
424
425 @Override
426 public boolean accept(Path entry) { return true; }
427
428 static final AcceptAllFilter FILTER = new AcceptAllFilter();
429 }
430
431 /**
432 * Opens a directory, returning a {@link DirectoryStream} to iterate over
433 * all entries in the directory. The elements returned by the directory
434 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
435 * Path}, each one representing an entry in the directory. The {@code Path}
436 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
437 * name of the directory entry against {@code dir}.
438 *
439 * <p> When not using the try-with-resources construct, then directory
440 * stream's {@code close} method should be invoked after iteration is
441 * completed so as to free any resources held for the open directory.
442 *
443 * <p> When an implementation supports operations on entries in the
444 * directory that execute in a race-free manner then the returned directory
445 * stream is a {@link SecureDirectoryStream}.
446 *
447 * @param dir
448 * the path to the directory
449 *
450 * @return a new and open {@code DirectoryStream} object
451 *
452 * @throws NotDirectoryException
453 * if the file could not otherwise be opened because it is not
454 * a directory <i>(optional specific exception)</i>
455 * @throws IOException
456 * if an I/O error occurs
457 * @throws SecurityException
458 * In the case of the default provider, and a security manager is
459 * installed, the {@link SecurityManager#checkRead(String) checkRead}
460 * method is invoked to check read access to the directory.
461 */
462 public static DirectoryStream<Path> newDirectoryStream(Path dir)
463 throws IOException
464 {
465 return provider(dir).newDirectoryStream(dir, AcceptAllFilter.FILTER);
466 }
467
468 /**
469 * Opens a directory, returning a {@link DirectoryStream} to iterate over
470 * the entries in the directory. The elements returned by the directory
471 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
472 * Path}, each one representing an entry in the directory. The {@code Path}
473 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
474 * name of the directory entry against {@code dir}. The entries returned by
475 * the iterator are filtered by matching the {@code String} representation
476 * of their file names against the given <em>globbing</em> pattern.
477 *
478 * <p> For example, suppose we want to iterate over the files ending with
479 * ".java" in a directory:
480 * <pre>
481 * Path dir = ...
482 * try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, "*.java")) {
483 * :
484 * }
485 * </pre>
486 *
487 * <p> The globbing pattern is specified by the {@link
488 * FileSystem#getPathMatcher getPathMatcher} method.
489 *
490 * <p> When not using the try-with-resources construct, then directory
491 * stream's {@code close} method should be invoked after iteration is
492 * completed so as to free any resources held for the open directory.
493 *
494 * <p> When an implementation supports operations on entries in the
495 * directory that execute in a race-free manner then the returned directory
496 * stream is a {@link SecureDirectoryStream}.
497 *
498 * @param dir
499 * the path to the directory
500 * @param glob
501 * the glob pattern
502 *
503 * @return a new and open {@code DirectoryStream} object
504 *
505 * @throws java.util.regex.PatternSyntaxException
506 * if the pattern is invalid
507 * @throws NotDirectoryException
508 * if the file could not otherwise be opened because it is not
509 * a directory <i>(optional specific exception)</i>
510 * @throws IOException
511 * if an I/O error occurs
512 * @throws SecurityException
513 * In the case of the default provider, and a security manager is
514 * installed, the {@link SecurityManager#checkRead(String) checkRead}
515 * method is invoked to check read access to the directory.
516 */
517 public static DirectoryStream<Path> newDirectoryStream(Path dir, String glob)
518 throws IOException
519 {
520 // avoid creating a matcher if all entries are required.
521 if (glob.equals("*"))
522 return newDirectoryStream(dir);
523
524 // create a matcher and return a filter that uses it.
525 FileSystem fs = dir.getFileSystem();
526 final PathMatcher matcher = fs.getPathMatcher("glob:" + glob);
527 DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<>() {
528 @Override
529 public boolean accept(Path entry) {
530 return matcher.matches(entry.getFileName());
531 }
532 };
533 return fs.provider().newDirectoryStream(dir, filter);
534 }
535
536 /**
537 * Opens a directory, returning a {@link DirectoryStream} to iterate over
538 * the entries in the directory. The elements returned by the directory
539 * stream's {@link DirectoryStream#iterator iterator} are of type {@code
540 * Path}, each one representing an entry in the directory. The {@code Path}
541 * objects are obtained as if by {@link Path#resolve(Path) resolving} the
542 * name of the directory entry against {@code dir}. The entries returned by
543 * the iterator are filtered by the given {@link DirectoryStream.Filter
544 * filter}.
545 *
546 * <p> When not using the try-with-resources construct, then directory
547 * stream's {@code close} method should be invoked after iteration is
548 * completed so as to free any resources held for the open directory.
549 *
550 * <p> Where the filter terminates due to an uncaught error or runtime
551 * exception then it is propagated to the {@link Iterator#hasNext()
552 * hasNext} or {@link Iterator#next() next} method. Where an {@code
553 * IOException} is thrown, it results in the {@code hasNext} or {@code
554 * next} method throwing a {@link DirectoryIteratorException} with the
555 * {@code IOException} as the cause.
556 *
557 * <p> When an implementation supports operations on entries in the
558 * directory that execute in a race-free manner then the returned directory
559 * stream is a {@link SecureDirectoryStream}.
560 *
561 * <p> <b>Usage Example:</b>
562 * Suppose we want to iterate over the files in a directory that are
563 * larger than 8K.
564 * <pre>
565 * DirectoryStream.Filter<Path> filter = new DirectoryStream.Filter<Path>() {
566 * public boolean accept(Path file) throws IOException {
567 * return (Files.size(file) > 8192L);
568 * }
569 * };
570 * Path dir = ...
571 * try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir, filter)) {
572 * :
573 * }
574 * </pre>
575 *
576 * @param dir
577 * the path to the directory
578 * @param filter
579 * the directory stream filter
580 *
581 * @return a new and open {@code DirectoryStream} object
582 *
583 * @throws NotDirectoryException
584 * if the file could not otherwise be opened because it is not
585 * a directory <i>(optional specific exception)</i>
586 * @throws IOException
587 * if an I/O error occurs
588 * @throws SecurityException
589 * In the case of the default provider, and a security manager is
590 * installed, the {@link SecurityManager#checkRead(String) checkRead}
591 * method is invoked to check read access to the directory.
592 */
593 public static DirectoryStream<Path> newDirectoryStream(Path dir,
594 DirectoryStream.Filter<? super Path> filter)
595 throws IOException
596 {
597 return provider(dir).newDirectoryStream(dir, filter);
598 }
599
600 // -- Creation and deletion --
601
602 /**
603 * Creates a new and empty file, failing if the file already exists. The
604 * check for the existence of the file and the creation of the new file if
605 * it does not exist are a single operation that is atomic with respect to
606 * all other filesystem activities that might affect the directory.
607 *
608 * <p> The {@code attrs} parameter is optional {@link FileAttribute
609 * file-attributes} to set atomically when creating the file. Each attribute
610 * is identified by its {@link FileAttribute#name name}. If more than one
611 * attribute of the same name is included in the array then all but the last
612 * occurrence is ignored.
613 *
614 * @param path
615 * the path to the file to create
616 * @param attrs
617 * an optional list of file attributes to set atomically when
618 * creating the file
619 *
620 * @return the file
621 *
622 * @throws UnsupportedOperationException
623 * if the array contains an attribute that cannot be set atomically
624 * when creating the file
625 * @throws FileAlreadyExistsException
626 * if a file of that name already exists
627 * <i>(optional specific exception)</i>
628 * @throws IOException
629 * if an I/O error occurs or the parent directory does not exist
630 * @throws SecurityException
631 * In the case of the default provider, and a security manager is
632 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
633 * method is invoked to check write access to the new file.
634 */
635 public static Path createFile(Path path, FileAttribute<?>... attrs)
636 throws IOException
637 {
638 EnumSet<StandardOpenOption> options =
639 EnumSet.<StandardOpenOption>of(StandardOpenOption.CREATE_NEW, StandardOpenOption.WRITE);
640 newByteChannel(path, options, attrs).close();
641 return path;
642 }
643
644 /**
645 * Creates a new directory. The check for the existence of the file and the
646 * creation of the directory if it does not exist are a single operation
647 * that is atomic with respect to all other filesystem activities that might
648 * affect the directory. The {@link #createDirectories createDirectories}
649 * method should be used where it is required to create all nonexistent
650 * parent directories first.
651 *
652 * <p> The {@code attrs} parameter is optional {@link FileAttribute
653 * file-attributes} to set atomically when creating the directory. Each
654 * attribute is identified by its {@link FileAttribute#name name}. If more
655 * than one attribute of the same name is included in the array then all but
656 * the last occurrence is ignored.
657 *
658 * @param dir
659 * the directory to create
660 * @param attrs
661 * an optional list of file attributes to set atomically when
662 * creating the directory
663 *
664 * @return the directory
665 *
666 * @throws UnsupportedOperationException
667 * if the array contains an attribute that cannot be set atomically
668 * when creating the directory
669 * @throws FileAlreadyExistsException
670 * if a directory could not otherwise be created because a file of
671 * that name already exists <i>(optional specific exception)</i>
672 * @throws IOException
673 * if an I/O error occurs or the parent directory does not exist
674 * @throws SecurityException
675 * In the case of the default provider, and a security manager is
676 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
677 * method is invoked to check write access to the new directory.
678 */
679 public static Path createDirectory(Path dir, FileAttribute<?>... attrs)
680 throws IOException
681 {
682 provider(dir).createDirectory(dir, attrs);
683 return dir;
684 }
685
686 /**
687 * Creates a directory by creating all nonexistent parent directories first.
688 * Unlike the {@link #createDirectory createDirectory} method, an exception
689 * is not thrown if the directory could not be created because it already
690 * exists.
691 *
692 * <p> The {@code attrs} parameter is optional {@link FileAttribute
693 * file-attributes} to set atomically when creating the nonexistent
694 * directories. Each file attribute is identified by its {@link
695 * FileAttribute#name name}. If more than one attribute of the same name is
696 * included in the array then all but the last occurrence is ignored.
697 *
698 * <p> If this method fails, then it may do so after creating some, but not
699 * all, of the parent directories.
700 *
701 * @param dir
702 * the directory to create
703 *
704 * @param attrs
705 * an optional list of file attributes to set atomically when
706 * creating the directory
707 *
708 * @return the directory
709 *
710 * @throws UnsupportedOperationException
711 * if the array contains an attribute that cannot be set atomically
712 * when creating the directory
713 * @throws FileAlreadyExistsException
714 * if {@code dir} exists but is not a directory <i>(optional specific
715 * exception)</i>
716 * @throws IOException
717 * if an I/O error occurs
718 * @throws SecurityException
719 * in the case of the default provider, and a security manager is
720 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
721 * method is invoked prior to attempting to create a directory and
722 * its {@link SecurityManager#checkRead(String) checkRead} is
723 * invoked for each parent directory that is checked. If {@code
724 * dir} is not an absolute path then its {@link Path#toAbsolutePath
725 * toAbsolutePath} may need to be invoked to get its absolute path.
726 * This may invoke the security manager's {@link
727 * SecurityManager#checkPropertyAccess(String) checkPropertyAccess}
728 * method to check access to the system property {@code user.dir}
729 */
730 public static Path createDirectories(Path dir, FileAttribute<?>... attrs)
731 throws IOException
732 {
733 // attempt to create the directory
734 try {
735 createAndCheckIsDirectory(dir, attrs);
736 return dir;
737 } catch (FileAlreadyExistsException x) {
738 // file exists and is not a directory
739 throw x;
740 } catch (IOException x) {
741 // parent may not exist or other reason
742 }
743 SecurityException se = null;
744 try {
745 dir = dir.toAbsolutePath();
746 } catch (SecurityException x) {
747 // don't have permission to get absolute path
748 se = x;
749 }
750 // find a descendant that exists
751 Path parent = dir.getParent();
752 while (parent != null) {
753 try {
754 provider(parent).checkAccess(parent);
755 break;
756 } catch (NoSuchFileException x) {
757 // does not exist
758 }
759 parent = parent.getParent();
760 }
761 if (parent == null) {
762 // unable to find existing parent
763 if (se == null) {
764 throw new FileSystemException(dir.toString(), null,
765 "Unable to determine if root directory exists");
766 } else {
767 throw se;
768 }
769 }
770
771 // create directories
772 Path child = parent;
773 for (Path name: parent.relativize(dir)) {
774 child = child.resolve(name);
775 createAndCheckIsDirectory(child, attrs);
776 }
777 return dir;
778 }
779
780 /**
781 * Used by createDirectories to attempt to create a directory. A no-op
782 * if the directory already exists.
783 */
784 private static void createAndCheckIsDirectory(Path dir,
785 FileAttribute<?>... attrs)
786 throws IOException
787 {
788 try {
789 createDirectory(dir, attrs);
790 } catch (FileAlreadyExistsException x) {
791 if (!isDirectory(dir, LinkOption.NOFOLLOW_LINKS))
792 throw x;
793 }
794 }
795
796 /**
797 * Creates a new empty file in the specified directory, using the given
798 * prefix and suffix strings to generate its name. The resulting
799 * {@code Path} is associated with the same {@code FileSystem} as the given
800 * directory.
801 *
802 * <p> The details as to how the name of the file is constructed is
803 * implementation dependent and therefore not specified. Where possible
804 * the {@code prefix} and {@code suffix} are used to construct candidate
805 * names in the same manner as the {@link
806 * java.io.File#createTempFile(String,String,File)} method.
807 *
808 * <p> As with the {@code File.createTempFile} methods, this method is only
809 * part of a temporary-file facility. Where used as a <em>work files</em>,
810 * the resulting file may be opened using the {@link
811 * StandardOpenOption#DELETE_ON_CLOSE DELETE_ON_CLOSE} option so that the
812 * file is deleted when the appropriate {@code close} method is invoked.
813 * Alternatively, a {@link Runtime#addShutdownHook shutdown-hook}, or the
814 * {@link java.io.File#deleteOnExit} mechanism may be used to delete the
815 * file automatically.
816 *
817 * <p> The {@code attrs} parameter is optional {@link FileAttribute
818 * file-attributes} to set atomically when creating the file. Each attribute
819 * is identified by its {@link FileAttribute#name name}. If more than one
820 * attribute of the same name is included in the array then all but the last
821 * occurrence is ignored. When no file attributes are specified, then the
822 * resulting file may have more restrictive access permissions to files
823 * created by the {@link java.io.File#createTempFile(String,String,File)}
824 * method.
825 *
826 * @param dir
827 * the path to directory in which to create the file
828 * @param prefix
829 * the prefix string to be used in generating the file's name;
830 * may be {@code null}
831 * @param suffix
832 * the suffix string to be used in generating the file's name;
833 * may be {@code null}, in which case "{@code .tmp}" is used
834 * @param attrs
835 * an optional list of file attributes to set atomically when
836 * creating the file
837 *
838 * @return the path to the newly created file that did not exist before
839 * this method was invoked
840 *
841 * @throws IllegalArgumentException
842 * if the prefix or suffix parameters cannot be used to generate
843 * a candidate file name
844 * @throws UnsupportedOperationException
845 * if the array contains an attribute that cannot be set atomically
846 * when creating the directory
847 * @throws IOException
848 * if an I/O error occurs or {@code dir} does not exist
849 * @throws SecurityException
850 * In the case of the default provider, and a security manager is
851 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
852 * method is invoked to check write access to the file.
853 */
854 public static Path createTempFile(Path dir,
855 String prefix,
856 String suffix,
857 FileAttribute<?>... attrs)
858 throws IOException
859 {
860 return TempFileHelper.createTempFile(Objects.requireNonNull(dir),
861 prefix, suffix, attrs);
862 }
863
864 /**
865 * Creates an empty file in the default temporary-file directory, using
866 * the given prefix and suffix to generate its name. The resulting {@code
867 * Path} is associated with the default {@code FileSystem}.
868 *
869 * <p> This method works in exactly the manner specified by the
870 * {@link #createTempFile(Path,String,String,FileAttribute[])} method for
871 * the case that the {@code dir} parameter is the temporary-file directory.
872 *
873 * @param prefix
874 * the prefix string to be used in generating the file's name;
875 * may be {@code null}
876 * @param suffix
877 * the suffix string to be used in generating the file's name;
878 * may be {@code null}, in which case "{@code .tmp}" is used
879 * @param attrs
880 * an optional list of file attributes to set atomically when
881 * creating the file
882 *
883 * @return the path to the newly created file that did not exist before
884 * this method was invoked
885 *
886 * @throws IllegalArgumentException
887 * if the prefix or suffix parameters cannot be used to generate
888 * a candidate file name
889 * @throws UnsupportedOperationException
890 * if the array contains an attribute that cannot be set atomically
891 * when creating the directory
892 * @throws IOException
893 * if an I/O error occurs or the temporary-file directory does not
894 * exist
895 * @throws SecurityException
896 * In the case of the default provider, and a security manager is
897 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
898 * method is invoked to check write access to the file.
899 */
900 public static Path createTempFile(String prefix,
901 String suffix,
902 FileAttribute<?>... attrs)
903 throws IOException
904 {
905 return TempFileHelper.createTempFile(null, prefix, suffix, attrs);
906 }
907
908 /**
909 * Creates a new directory in the specified directory, using the given
910 * prefix to generate its name. The resulting {@code Path} is associated
911 * with the same {@code FileSystem} as the given directory.
912 *
913 * <p> The details as to how the name of the directory is constructed is
914 * implementation dependent and therefore not specified. Where possible
915 * the {@code prefix} is used to construct candidate names.
916 *
917 * <p> As with the {@code createTempFile} methods, this method is only
918 * part of a temporary-file facility. A {@link Runtime#addShutdownHook
919 * shutdown-hook}, or the {@link java.io.File#deleteOnExit} mechanism may be
920 * used to delete the directory automatically.
921 *
922 * <p> The {@code attrs} parameter is optional {@link FileAttribute
923 * file-attributes} to set atomically when creating the directory. Each
924 * attribute is identified by its {@link FileAttribute#name name}. If more
925 * than one attribute of the same name is included in the array then all but
926 * the last occurrence is ignored.
927 *
928 * @param dir
929 * the path to directory in which to create the directory
930 * @param prefix
931 * the prefix string to be used in generating the directory's name;
932 * may be {@code null}
933 * @param attrs
934 * an optional list of file attributes to set atomically when
935 * creating the directory
936 *
937 * @return the path to the newly created directory that did not exist before
938 * this method was invoked
939 *
940 * @throws IllegalArgumentException
941 * if the prefix cannot be used to generate a candidate directory name
942 * @throws UnsupportedOperationException
943 * if the array contains an attribute that cannot be set atomically
944 * when creating the directory
945 * @throws IOException
946 * if an I/O error occurs or {@code dir} does not exist
947 * @throws SecurityException
948 * In the case of the default provider, and a security manager is
949 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
950 * method is invoked to check write access when creating the
951 * directory.
952 */
953 public static Path createTempDirectory(Path dir,
954 String prefix,
955 FileAttribute<?>... attrs)
956 throws IOException
957 {
958 return TempFileHelper.createTempDirectory(Objects.requireNonNull(dir),
959 prefix, attrs);
960 }
961
962 /**
963 * Creates a new directory in the default temporary-file directory, using
964 * the given prefix to generate its name. The resulting {@code Path} is
965 * associated with the default {@code FileSystem}.
966 *
967 * <p> This method works in exactly the manner specified by {@link
968 * #createTempDirectory(Path,String,FileAttribute[])} method for the case
969 * that the {@code dir} parameter is the temporary-file directory.
970 *
971 * @param prefix
972 * the prefix string to be used in generating the directory's name;
973 * may be {@code null}
974 * @param attrs
975 * an optional list of file attributes to set atomically when
976 * creating the directory
977 *
978 * @return the path to the newly created directory that did not exist before
979 * this method was invoked
980 *
981 * @throws IllegalArgumentException
982 * if the prefix cannot be used to generate a candidate directory name
983 * @throws UnsupportedOperationException
984 * if the array contains an attribute that cannot be set atomically
985 * when creating the directory
986 * @throws IOException
987 * if an I/O error occurs or the temporary-file directory does not
988 * exist
989 * @throws SecurityException
990 * In the case of the default provider, and a security manager is
991 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
992 * method is invoked to check write access when creating the
993 * directory.
994 */
995 public static Path createTempDirectory(String prefix,
996 FileAttribute<?>... attrs)
997 throws IOException
998 {
999 return TempFileHelper.createTempDirectory(null, prefix, attrs);
1000 }
1001
1002 /**
1003 * Creates a symbolic link to a target <i>(optional operation)</i>.
1004 *
1005 * <p> The {@code target} parameter is the target of the link. It may be an
1006 * {@link Path#isAbsolute absolute} or relative path and may not exist. When
1007 * the target is a relative path then file system operations on the resulting
1008 * link are relative to the path of the link.
1009 *
1010 * <p> The {@code attrs} parameter is optional {@link FileAttribute
1011 * attributes} to set atomically when creating the link. Each attribute is
1012 * identified by its {@link FileAttribute#name name}. If more than one attribute
1013 * of the same name is included in the array then all but the last occurrence
1014 * is ignored.
1015 *
1016 * <p> Where symbolic links are supported, but the underlying {@link FileStore}
1017 * does not support symbolic links, then this may fail with an {@link
1018 * IOException}. Additionally, some operating systems may require that the
1019 * Java virtual machine be started with implementation specific privileges to
1020 * create symbolic links, in which case this method may throw {@code IOException}.
1021 *
1022 * @param link
1023 * the path of the symbolic link to create
1024 * @param target
1025 * the target of the symbolic link
1026 * @param attrs
1027 * the array of attributes to set atomically when creating the
1028 * symbolic link
1029 *
1030 * @return the path to the symbolic link
1031 *
1032 * @throws UnsupportedOperationException
1033 * if the implementation does not support symbolic links or the
1034 * array contains an attribute that cannot be set atomically when
1035 * creating the symbolic link
1036 * @throws FileAlreadyExistsException
1037 * if a file with the name already exists <i>(optional specific
1038 * exception)</i>
1039 * @throws IOException
1040 * if an I/O error occurs
1041 * @throws SecurityException
1042 * In the case of the default provider, and a security manager
1043 * is installed, it denies {@link LinkPermission}{@code ("symbolic")}
1044 * or its {@link SecurityManager#checkWrite(String) checkWrite}
1045 * method denies write access to the path of the symbolic link.
1046 */
1047 public static Path createSymbolicLink(Path link, Path target,
1048 FileAttribute<?>... attrs)
1049 throws IOException
1050 {
1051 provider(link).createSymbolicLink(link, target, attrs);
1052 return link;
1053 }
1054
1055 /**
1056 * Creates a new link (directory entry) for an existing file <i>(optional
1057 * operation)</i>.
1058 *
1059 * <p> The {@code link} parameter locates the directory entry to create.
1060 * The {@code existing} parameter is the path to an existing file. This
1061 * method creates a new directory entry for the file so that it can be
1062 * accessed using {@code link} as the path. On some file systems this is
1063 * known as creating a "hard link". Whether the file attributes are
1064 * maintained for the file or for each directory entry is file system
1065 * specific and therefore not specified. Typically, a file system requires
1066 * that all links (directory entries) for a file be on the same file system.
1067 * Furthermore, on some platforms, the Java virtual machine may require to
1068 * be started with implementation specific privileges to create hard links
1069 * or to create links to directories.
1070 *
1071 * @param link
1072 * the link (directory entry) to create
1073 * @param existing
1074 * a path to an existing file
1075 *
1076 * @return the path to the link (directory entry)
1077 *
1078 * @throws UnsupportedOperationException
1079 * if the implementation does not support adding an existing file
1080 * to a directory
1081 * @throws FileAlreadyExistsException
1082 * if the entry could not otherwise be created because a file of
1083 * that name already exists <i>(optional specific exception)</i>
1084 * @throws IOException
1085 * if an I/O error occurs
1086 * @throws SecurityException
1087 * In the case of the default provider, and a security manager
1088 * is installed, it denies {@link LinkPermission}{@code ("hard")}
1089 * or its {@link SecurityManager#checkWrite(String) checkWrite}
1090 * method denies write access to either the link or the
1091 * existing file.
1092 */
1093 public static Path createLink(Path link, Path existing) throws IOException {
1094 provider(link).createLink(link, existing);
1095 return link;
1096 }
1097
1098 /**
1099 * Deletes a file.
1100 *
1101 * <p> An implementation may require to examine the file to determine if the
1102 * file is a directory. Consequently this method may not be atomic with respect
1103 * to other file system operations. If the file is a symbolic link then the
1104 * symbolic link itself, not the final target of the link, is deleted.
1105 *
1106 * <p> If the file is a directory then the directory must be empty. In some
1107 * implementations a directory has entries for special files or links that
1108 * are created when the directory is created. In such implementations a
1109 * directory is considered empty when only the special entries exist.
1110 * This method can be used with the {@link #walkFileTree walkFileTree}
1111 * method to delete a directory and all entries in the directory, or an
1112 * entire <i>file-tree</i> where required.
1113 *
1114 * <p> On some operating systems it may not be possible to remove a file when
1115 * it is open and in use by this Java virtual machine or other programs.
1116 *
1117 * @param path
1118 * the path to the file to delete
1119 *
1120 * @throws NoSuchFileException
1121 * if the file does not exist <i>(optional specific exception)</i>
1122 * @throws DirectoryNotEmptyException
1123 * if the file is a directory and could not otherwise be deleted
1124 * because the directory is not empty <i>(optional specific
1125 * exception)</i>
1126 * @throws IOException
1127 * if an I/O error occurs
1128 * @throws SecurityException
1129 * In the case of the default provider, and a security manager is
1130 * installed, the {@link SecurityManager#checkDelete(String)} method
1131 * is invoked to check delete access to the file
1132 */
1133 public static void delete(Path path) throws IOException {
1134 provider(path).delete(path);
1135 }
1136
1137 /**
1138 * Deletes a file if it exists.
1139 *
1140 * <p> As with the {@link #delete(Path) delete(Path)} method, an
1141 * implementation may need to examine the file to determine if the file is a
1142 * directory. Consequently this method may not be atomic with respect to
1143 * other file system operations. If the file is a symbolic link, then the
1144 * symbolic link itself, not the final target of the link, is deleted.
1145 *
1146 * <p> If the file is a directory then the directory must be empty. In some
1147 * implementations a directory has entries for special files or links that
1148 * are created when the directory is created. In such implementations a
1149 * directory is considered empty when only the special entries exist.
1150 *
1151 * <p> On some operating systems it may not be possible to remove a file when
1152 * it is open and in use by this Java virtual machine or other programs.
1153 *
1154 * @param path
1155 * the path to the file to delete
1156 *
1157 * @return {@code true} if the file was deleted by this method; {@code
1158 * false} if the file could not be deleted because it did not
1159 * exist
1160 *
1161 * @throws DirectoryNotEmptyException
1162 * if the file is a directory and could not otherwise be deleted
1163 * because the directory is not empty <i>(optional specific
1164 * exception)</i>
1165 * @throws IOException
1166 * if an I/O error occurs
1167 * @throws SecurityException
1168 * In the case of the default provider, and a security manager is
1169 * installed, the {@link SecurityManager#checkDelete(String)} method
1170 * is invoked to check delete access to the file.
1171 */
1172 public static boolean deleteIfExists(Path path) throws IOException {
1173 return provider(path).deleteIfExists(path);
1174 }
1175
1176 // -- Copying and moving files --
1177
1178 /**
1179 * Copy a file to a target file.
1180 *
1181 * <p> This method copies a file to the target file with the {@code
1182 * options} parameter specifying how the copy is performed. By default, the
1183 * copy fails if the target file already exists or is a symbolic link,
1184 * except if the source and target are the {@link #isSameFile same} file, in
1185 * which case the method completes without copying the file. File attributes
1186 * are not required to be copied to the target file. If symbolic links are
1187 * supported, and the file is a symbolic link, then the final target of the
1188 * link is copied. If the file is a directory then it creates an empty
1189 * directory in the target location (entries in the directory are not
1190 * copied). This method can be used with the {@link #walkFileTree
1191 * walkFileTree} method to copy a directory and all entries in the directory,
1192 * or an entire <i>file-tree</i> where required.
1193 *
1194 * <p> The {@code options} parameter may include any of the following:
1195 *
1196 * <table class="striped">
1197 * <caption style="display:none">Options</caption>
1198 * <thead>
1199 * <tr> <th scope="col">Option</th> <th scope="col">Description</th> </tr>
1200 * </thead>
1201 * <tbody>
1202 * <tr>
1203 * <th scope="row"> {@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING} </th>
1204 * <td> If the target file exists, then the target file is replaced if it
1205 * is not a non-empty directory. If the target file exists and is a
1206 * symbolic link, then the symbolic link itself, not the target of
1207 * the link, is replaced. </td>
1208 * </tr>
1209 * <tr>
1210 * <th scope="row"> {@link StandardCopyOption#COPY_ATTRIBUTES COPY_ATTRIBUTES} </th>
1211 * <td> Attempts to copy the file attributes associated with this file to
1212 * the target file. The exact file attributes that are copied is platform
1213 * and file system dependent and therefore unspecified. Minimally, the
1214 * {@link BasicFileAttributes#lastModifiedTime last-modified-time} is
1215 * copied to the target file if supported by both the source and target
1216 * file stores. Copying of file timestamps may result in precision
1217 * loss. </td>
1218 * </tr>
1219 * <tr>
1220 * <th scope="row"> {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} </th>
1221 * <td> Symbolic links are not followed. If the file is a symbolic link,
1222 * then the symbolic link itself, not the target of the link, is copied.
1223 * It is implementation specific if file attributes can be copied to the
1224 * new link. In other words, the {@code COPY_ATTRIBUTES} option may be
1225 * ignored when copying a symbolic link. </td>
1226 * </tr>
1227 * </tbody>
1228 * </table>
1229 *
1230 * <p> An implementation of this interface may support additional
1231 * implementation specific options.
1232 *
1233 * <p> Copying a file is not an atomic operation. If an {@link IOException}
1234 * is thrown, then it is possible that the target file is incomplete or some
1235 * of its file attributes have not been copied from the source file. When
1236 * the {@code REPLACE_EXISTING} option is specified and the target file
1237 * exists, then the target file is replaced. The check for the existence of
1238 * the file and the creation of the new file may not be atomic with respect
1239 * to other file system activities.
1240 *
1241 * <p> <b>Usage Example:</b>
1242 * Suppose we want to copy a file into a directory, giving it the same file
1243 * name as the source file:
1244 * <pre>
1245 * Path source = ...
1246 * Path newdir = ...
1247 * Files.copy(source, newdir.resolve(source.getFileName());
1248 * </pre>
1249 *
1250 * @param source
1251 * the path to the file to copy
1252 * @param target
1253 * the path to the target file (may be associated with a different
1254 * provider to the source path)
1255 * @param options
1256 * options specifying how the copy should be done
1257 *
1258 * @return the path to the target file
1259 *
1260 * @throws UnsupportedOperationException
1261 * if the array contains a copy option that is not supported
1262 * @throws FileAlreadyExistsException
1263 * if the target file exists but cannot be replaced because the
1264 * {@code REPLACE_EXISTING} option is not specified <i>(optional
1265 * specific exception)</i>
1266 * @throws DirectoryNotEmptyException
1267 * the {@code REPLACE_EXISTING} option is specified but the file
1268 * cannot be replaced because it is a non-empty directory
1269 * <i>(optional specific exception)</i>
1270 * @throws IOException
1271 * if an I/O error occurs
1272 * @throws SecurityException
1273 * In the case of the default provider, and a security manager is
1274 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1275 * method is invoked to check read access to the source file, the
1276 * {@link SecurityManager#checkWrite(String) checkWrite} is invoked
1277 * to check write access to the target file. If a symbolic link is
1278 * copied the security manager is invoked to check {@link
1279 * LinkPermission}{@code ("symbolic")}.
1280 */
1281 public static Path copy(Path source, Path target, CopyOption... options)
1282 throws IOException
1283 {
1284 FileSystemProvider provider = provider(source);
1285 if (provider(target) == provider) {
1286 // same provider
1287 provider.copy(source, target, options);
1288 } else {
1289 // different providers
1290 CopyMoveHelper.copyToForeignTarget(source, target, options);
1291 }
1292 return target;
1293 }
1294
1295 /**
1296 * Move or rename a file to a target file.
1297 *
1298 * <p> By default, this method attempts to move the file to the target
1299 * file, failing if the target file exists except if the source and
1300 * target are the {@link #isSameFile same} file, in which case this method
1301 * has no effect. If the file is a symbolic link then the symbolic link
1302 * itself, not the target of the link, is moved. This method may be
1303 * invoked to move an empty directory. In some implementations a directory
1304 * has entries for special files or links that are created when the
1305 * directory is created. In such implementations a directory is considered
1306 * empty when only the special entries exist. When invoked to move a
1307 * directory that is not empty then the directory is moved if it does not
1308 * require moving the entries in the directory. For example, renaming a
1309 * directory on the same {@link FileStore} will usually not require moving
1310 * the entries in the directory. When moving a directory requires that its
1311 * entries be moved then this method fails (by throwing an {@code
1312 * IOException}). To move a <i>file tree</i> may involve copying rather
1313 * than moving directories and this can be done using the {@link
1314 * #copy copy} method in conjunction with the {@link
1315 * #walkFileTree Files.walkFileTree} utility method.
1316 *
1317 * <p> The {@code options} parameter may include any of the following:
1318 *
1319 * <table class="striped">
1320 * <caption style="display:none">Options</caption>
1321 * <thead>
1322 * <tr> <th scope="col">Option</th> <th scope="col">Description</th> </tr>
1323 * </thead>
1324 * <tbody>
1325 * <tr>
1326 * <th scope="row"> {@link StandardCopyOption#REPLACE_EXISTING REPLACE_EXISTING} </th>
1327 * <td> If the target file exists, then the target file is replaced if it
1328 * is not a non-empty directory. If the target file exists and is a
1329 * symbolic link, then the symbolic link itself, not the target of
1330 * the link, is replaced. </td>
1331 * </tr>
1332 * <tr>
1333 * <th scope="row"> {@link StandardCopyOption#ATOMIC_MOVE ATOMIC_MOVE} </th>
1334 * <td> The move is performed as an atomic file system operation and all
1335 * other options are ignored. If the target file exists then it is
1336 * implementation specific if the existing file is replaced or this method
1337 * fails by throwing an {@link IOException}. If the move cannot be
1338 * performed as an atomic file system operation then {@link
1339 * AtomicMoveNotSupportedException} is thrown. This can arise, for
1340 * example, when the target location is on a different {@code FileStore}
1341 * and would require that the file be copied, or target location is
1342 * associated with a different provider to this object. </td>
1343 * </tbody>
1344 * </table>
1345 *
1346 * <p> An implementation of this interface may support additional
1347 * implementation specific options.
1348 *
1349 * <p> Moving a file will copy the {@link
1350 * BasicFileAttributes#lastModifiedTime last-modified-time} to the target
1351 * file if supported by both source and target file stores. Copying of file
1352 * timestamps may result in precision loss. An implementation may also
1353 * attempt to copy other file attributes but is not required to fail if the
1354 * file attributes cannot be copied. When the move is performed as
1355 * a non-atomic operation, and an {@code IOException} is thrown, then the
1356 * state of the files is not defined. The original file and the target file
1357 * may both exist, the target file may be incomplete or some of its file
1358 * attributes may not been copied from the original file.
1359 *
1360 * <p> <b>Usage Examples:</b>
1361 * Suppose we want to rename a file to "newname", keeping the file in the
1362 * same directory:
1363 * <pre>
1364 * Path source = ...
1365 * Files.move(source, source.resolveSibling("newname"));
1366 * </pre>
1367 * Alternatively, suppose we want to move a file to new directory, keeping
1368 * the same file name, and replacing any existing file of that name in the
1369 * directory:
1370 * <pre>
1371 * Path source = ...
1372 * Path newdir = ...
1373 * Files.move(source, newdir.resolve(source.getFileName()), REPLACE_EXISTING);
1374 * </pre>
1375 *
1376 * @param source
1377 * the path to the file to move
1378 * @param target
1379 * the path to the target file (may be associated with a different
1380 * provider to the source path)
1381 * @param options
1382 * options specifying how the move should be done
1383 *
1384 * @return the path to the target file
1385 *
1386 * @throws UnsupportedOperationException
1387 * if the array contains a copy option that is not supported
1388 * @throws FileAlreadyExistsException
1389 * if the target file exists but cannot be replaced because the
1390 * {@code REPLACE_EXISTING} option is not specified <i>(optional
1391 * specific exception)</i>
1392 * @throws DirectoryNotEmptyException
1393 * the {@code REPLACE_EXISTING} option is specified but the file
1394 * cannot be replaced because it is a non-empty directory
1395 * <i>(optional specific exception)</i>
1396 * @throws AtomicMoveNotSupportedException
1397 * if the options array contains the {@code ATOMIC_MOVE} option but
1398 * the file cannot be moved as an atomic file system operation.
1399 * @throws IOException
1400 * if an I/O error occurs
1401 * @throws SecurityException
1402 * In the case of the default provider, and a security manager is
1403 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
1404 * method is invoked to check write access to both the source and
1405 * target file.
1406 */
1407 public static Path move(Path source, Path target, CopyOption... options)
1408 throws IOException
1409 {
1410 FileSystemProvider provider = provider(source);
1411 if (provider(target) == provider) {
1412 // same provider
1413 provider.move(source, target, options);
1414 } else {
1415 // different providers
1416 CopyMoveHelper.moveToForeignTarget(source, target, options);
1417 }
1418 return target;
1419 }
1420
1421 // -- Miscellaneous --
1422
1423 /**
1424 * Reads the target of a symbolic link <i>(optional operation)</i>.
1425 *
1426 * <p> If the file system supports <a href="package-summary.html#links">symbolic
1427 * links</a> then this method is used to read the target of the link, failing
1428 * if the file is not a symbolic link. The target of the link need not exist.
1429 * The returned {@code Path} object will be associated with the same file
1430 * system as {@code link}.
1431 *
1432 * @param link
1433 * the path to the symbolic link
1434 *
1435 * @return a {@code Path} object representing the target of the link
1436 *
1437 * @throws UnsupportedOperationException
1438 * if the implementation does not support symbolic links
1439 * @throws NotLinkException
1440 * if the target could otherwise not be read because the file
1441 * is not a symbolic link <i>(optional specific exception)</i>
1442 * @throws IOException
1443 * if an I/O error occurs
1444 * @throws SecurityException
1445 * In the case of the default provider, and a security manager
1446 * is installed, it checks that {@code FilePermission} has been
1447 * granted with the "{@code readlink}" action to read the link.
1448 */
1449 public static Path readSymbolicLink(Path link) throws IOException {
1450 return provider(link).readSymbolicLink(link);
1451 }
1452
1453 /**
1454 * Returns the {@link FileStore} representing the file store where a file
1455 * is located.
1456 *
1457 * <p> Once a reference to the {@code FileStore} is obtained it is
1458 * implementation specific if operations on the returned {@code FileStore},
1459 * or {@link FileStoreAttributeView} objects obtained from it, continue
1460 * to depend on the existence of the file. In particular the behavior is not
1461 * defined for the case that the file is deleted or moved to a different
1462 * file store.
1463 *
1464 * @param path
1465 * the path to the file
1466 *
1467 * @return the file store where the file is stored
1468 *
1469 * @throws IOException
1470 * if an I/O error occurs
1471 * @throws SecurityException
1472 * In the case of the default provider, and a security manager is
1473 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1474 * method is invoked to check read access to the file, and in
1475 * addition it checks
1476 * {@link RuntimePermission}{@code ("getFileStoreAttributes")}
1477 */
1478 public static FileStore getFileStore(Path path) throws IOException {
1479 return provider(path).getFileStore(path);
1480 }
1481
1482 /**
1483 * Tests if two paths locate the same file.
1484 *
1485 * <p> If both {@code Path} objects are {@link Path#equals(Object) equal}
1486 * then this method returns {@code true} without checking if the file exists.
1487 * If the two {@code Path} objects are associated with different providers
1488 * then this method returns {@code false}. Otherwise, this method checks if
1489 * both {@code Path} objects locate the same file, and depending on the
1490 * implementation, may require to open or access both files.
1491 *
1492 * <p> If the file system and files remain static, then this method implements
1493 * an equivalence relation for non-null {@code Paths}.
1494 * <ul>
1495 * <li>It is <i>reflexive</i>: for {@code Path} {@code f},
1496 * {@code isSameFile(f,f)} should return {@code true}.
1497 * <li>It is <i>symmetric</i>: for two {@code Paths} {@code f} and {@code g},
1498 * {@code isSameFile(f,g)} will equal {@code isSameFile(g,f)}.
1499 * <li>It is <i>transitive</i>: for three {@code Paths}
1500 * {@code f}, {@code g}, and {@code h}, if {@code isSameFile(f,g)} returns
1501 * {@code true} and {@code isSameFile(g,h)} returns {@code true}, then
1502 * {@code isSameFile(f,h)} will return {@code true}.
1503 * </ul>
1504 *
1505 * @param path
1506 * one path to the file
1507 * @param path2
1508 * the other path
1509 *
1510 * @return {@code true} if, and only if, the two paths locate the same file
1511 *
1512 * @throws IOException
1513 * if an I/O error occurs
1514 * @throws SecurityException
1515 * In the case of the default provider, and a security manager is
1516 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1517 * method is invoked to check read access to both files.
1518 *
1519 * @see java.nio.file.attribute.BasicFileAttributes#fileKey
1520 */
1521 public static boolean isSameFile(Path path, Path path2) throws IOException {
1522 return provider(path).isSameFile(path, path2);
1523 }
1524
1525 /**
1526 * Tests if the content of two files is identical. This method extends the
1527 * {@link #isSameFile(java.nio.file.Path, java.nio.file.Path) isSameFile}
1528 * method to further compare the content of the two files.
1529 *
1530 * <p> It always returns true when path and path2:
1531 *
1532 * <ul>
1533 * <li> point to the same object, even if the file does not exist;
1534 * </li>
1535 * <li> are equals as determined by
1536 * {@link #isSameFile(java.nio.file.Path, java.nio.file.Path) isSameFile(path, path2)}
1537 * </li>
1538 * </ul>
1539 *
1540 * <p> If {@code isSameFile(path, path2)} returns false, this method will proceed
1541 * to read the files and compare them byte by byte to determine if they contain
1542 * the same content. It is assumed that the two files remain static during
1543 * the comparison process.
1544 *
1545 *
1546 * @param path
1547 * the path to a file
1548 * @param path2
1549 * the path to another file
1550 *
1551 * @return a boolean indicating whether path and path2 locate the same file or
1552 * their contents are identical.
1553 *
1554 * @throws IOException
1555 * if an I/O error occurs
1556 * @throws SecurityException
1557 * In the case of the default provider, and a security manager is
1558 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1559 * method is invoked to check read access to both files.
1560 *
1561 * @since 11
1562 */
1563 public static boolean isSameContent(Path path, Path path2) throws IOException {
1564 if (isSameFile(path, path2)) {
1565 return true;
1566 }
1567
1568 final long size = Files.size(path);
1569 if (size != Files.size(path2)) {
1570 return false;
1571 }
1572
1573 try (SeekableByteChannel sbc = Files.newByteChannel(path);
1574 InputStream in = Channels.newInputStream(sbc);
1575 SeekableByteChannel sbc2 = Files.newByteChannel(path2);
1576 InputStream in2 = Channels.newInputStream(sbc2);) {
1577
1578 byte[] buf = new byte[BUFFER_SIZE];
1579 byte[] buf2 = new byte[BUFFER_SIZE];
1580 int n, n2;
1581 while ((n = in.read(buf)) > 0) {
1582 n2 = in2.read(buf2);
1583 // unless the file is changed, n and n2 shall equal since in the previous
1584 // step we've made sure the file sizes are equal
1585 if (n != n2) {
1586 return false;
1587 }
1588
1589 if (n == BUFFER_SIZE) {
1590 if (!Arrays.equals(buf, buf2)) {
1591 return false;
1592 }
1593 } else {
1594 if (!Arrays.equals(buf, 0, n, buf2, 0, n2)) {
1595 return false;
1596 }
1597 }
1598 }
1599 }
1600 return true;
1601 }
1602
1603 /**
1604 * Tells whether or not a file is considered <em>hidden</em>. The exact
1605 * definition of hidden is platform or provider dependent. On UNIX for
1606 * example a file is considered to be hidden if its name begins with a
1607 * period character ('.'). On Windows a file is considered hidden if it
1608 * isn't a directory and the DOS {@link DosFileAttributes#isHidden hidden}
1609 * attribute is set.
1610 *
1611 * <p> Depending on the implementation this method may require to access
1612 * the file system to determine if the file is considered hidden.
1613 *
1614 * @param path
1615 * the path to the file to test
1616 *
1617 * @return {@code true} if the file is considered hidden
1618 *
1619 * @throws IOException
1620 * if an I/O error occurs
1621 * @throws SecurityException
1622 * In the case of the default provider, and a security manager is
1623 * installed, the {@link SecurityManager#checkRead(String) checkRead}
1624 * method is invoked to check read access to the file.
1625 */
1626 public static boolean isHidden(Path path) throws IOException {
1627 return provider(path).isHidden(path);
1628 }
1629
1630 // lazy loading of default and installed file type detectors
1631 private static class FileTypeDetectors{
1632 static final FileTypeDetector defaultFileTypeDetector =
1633 createDefaultFileTypeDetector();
1634 static final List<FileTypeDetector> installedDetectors =
1635 loadInstalledDetectors();
1636
1637 // creates the default file type detector
1638 private static FileTypeDetector createDefaultFileTypeDetector() {
1639 return AccessController
1640 .doPrivileged(new PrivilegedAction<>() {
1641 @Override public FileTypeDetector run() {
1642 return sun.nio.fs.DefaultFileTypeDetector.create();
1643 }});
1644 }
1645
1646 // loads all installed file type detectors
1647 private static List<FileTypeDetector> loadInstalledDetectors() {
1648 return AccessController
1649 .doPrivileged(new PrivilegedAction<>() {
1650 @Override public List<FileTypeDetector> run() {
1651 List<FileTypeDetector> list = new ArrayList<>();
1652 ServiceLoader<FileTypeDetector> loader = ServiceLoader
1653 .load(FileTypeDetector.class, ClassLoader.getSystemClassLoader());
1654 for (FileTypeDetector detector: loader) {
1655 list.add(detector);
1656 }
1657 return list;
1658 }});
1659 }
1660 }
1661
1662 /**
1663 * Probes the content type of a file.
1664 *
1665 * <p> This method uses the installed {@link FileTypeDetector} implementations
1666 * to probe the given file to determine its content type. Each file type
1667 * detector's {@link FileTypeDetector#probeContentType probeContentType} is
1668 * invoked, in turn, to probe the file type. If the file is recognized then
1669 * the content type is returned. If the file is not recognized by any of the
1670 * installed file type detectors then a system-default file type detector is
1671 * invoked to guess the content type.
1672 *
1673 * <p> A given invocation of the Java virtual machine maintains a system-wide
1674 * list of file type detectors. Installed file type detectors are loaded
1675 * using the service-provider loading facility defined by the {@link ServiceLoader}
1676 * class. Installed file type detectors are loaded using the system class
1677 * loader. If the system class loader cannot be found then the platform class
1678 * loader is used. File type detectors are typically installed
1679 * by placing them in a JAR file on the application class path,
1680 * the JAR file contains a provider-configuration file
1681 * named {@code java.nio.file.spi.FileTypeDetector} in the resource directory
1682 * {@code META-INF/services}, and the file lists one or more fully-qualified
1683 * names of concrete subclass of {@code FileTypeDetector } that have a zero
1684 * argument constructor. If the process of locating or instantiating the
1685 * installed file type detectors fails then an unspecified error is thrown.
1686 * The ordering that installed providers are located is implementation
1687 * specific.
1688 *
1689 * <p> The return value of this method is the string form of the value of a
1690 * Multipurpose Internet Mail Extension (MIME) content type as
1691 * defined by <a href="http://www.ietf.org/rfc/rfc2045.txt"><i>RFC 2045:
1692 * Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet
1693 * Message Bodies</i></a>. The string is guaranteed to be parsable according
1694 * to the grammar in the RFC.
1695 *
1696 * @param path
1697 * the path to the file to probe
1698 *
1699 * @return The content type of the file, or {@code null} if the content
1700 * type cannot be determined
1701 *
1702 * @throws IOException
1703 * if an I/O error occurs
1704 * @throws SecurityException
1705 * If a security manager is installed and it denies an unspecified
1706 * permission required by a file type detector implementation.
1707 */
1708 public static String probeContentType(Path path)
1709 throws IOException
1710 {
1711 // try installed file type detectors
1712 for (FileTypeDetector detector: FileTypeDetectors.installedDetectors) {
1713 String result = detector.probeContentType(path);
1714 if (result != null)
1715 return result;
1716 }
1717
1718 // fallback to default
1719 return FileTypeDetectors.defaultFileTypeDetector.probeContentType(path);
1720 }
1721
1722 // -- File Attributes --
1723
1724 /**
1725 * Returns a file attribute view of a given type.
1726 *
1727 * <p> A file attribute view provides a read-only or updatable view of a
1728 * set of file attributes. This method is intended to be used where the file
1729 * attribute view defines type-safe methods to read or update the file
1730 * attributes. The {@code type} parameter is the type of the attribute view
1731 * required and the method returns an instance of that type if supported.
1732 * The {@link BasicFileAttributeView} type supports access to the basic
1733 * attributes of a file. Invoking this method to select a file attribute
1734 * view of that type will always return an instance of that class.
1735 *
1736 * <p> The {@code options} array may be used to indicate how symbolic links
1737 * are handled by the resulting file attribute view for the case that the
1738 * file is a symbolic link. By default, symbolic links are followed. If the
1739 * option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is present then
1740 * symbolic links are not followed. This option is ignored by implementations
1741 * that do not support symbolic links.
1742 *
1743 * <p> <b>Usage Example:</b>
1744 * Suppose we want read or set a file's ACL, if supported:
1745 * <pre>
1746 * Path path = ...
1747 * AclFileAttributeView view = Files.getFileAttributeView(path, AclFileAttributeView.class);
1748 * if (view != null) {
1749 * List<AclEntry> acl = view.getAcl();
1750 * :
1751 * }
1752 * </pre>
1753 *
1754 * @param <V>
1755 * The {@code FileAttributeView} type
1756 * @param path
1757 * the path to the file
1758 * @param type
1759 * the {@code Class} object corresponding to the file attribute view
1760 * @param options
1761 * options indicating how symbolic links are handled
1762 *
1763 * @return a file attribute view of the specified type, or {@code null} if
1764 * the attribute view type is not available
1765 */
1766 public static <V extends FileAttributeView> V getFileAttributeView(Path path,
1767 Class<V> type,
1768 LinkOption... options)
1769 {
1770 return provider(path).getFileAttributeView(path, type, options);
1771 }
1772
1773 /**
1774 * Reads a file's attributes as a bulk operation.
1775 *
1776 * <p> The {@code type} parameter is the type of the attributes required
1777 * and this method returns an instance of that type if supported. All
1778 * implementations support a basic set of file attributes and so invoking
1779 * this method with a {@code type} parameter of {@code
1780 * BasicFileAttributes.class} will not throw {@code
1781 * UnsupportedOperationException}.
1782 *
1783 * <p> The {@code options} array may be used to indicate how symbolic links
1784 * are handled for the case that the file is a symbolic link. By default,
1785 * symbolic links are followed and the file attribute of the final target
1786 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1787 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1788 *
1789 * <p> It is implementation specific if all file attributes are read as an
1790 * atomic operation with respect to other file system operations.
1791 *
1792 * <p> <b>Usage Example:</b>
1793 * Suppose we want to read a file's attributes in bulk:
1794 * <pre>
1795 * Path path = ...
1796 * BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class);
1797 * </pre>
1798 * Alternatively, suppose we want to read file's POSIX attributes without
1799 * following symbolic links:
1800 * <pre>
1801 * PosixFileAttributes attrs =
1802 * Files.readAttributes(path, PosixFileAttributes.class, NOFOLLOW_LINKS);
1803 * </pre>
1804 *
1805 * @param <A>
1806 * The {@code BasicFileAttributes} type
1807 * @param path
1808 * the path to the file
1809 * @param type
1810 * the {@code Class} of the file attributes required
1811 * to read
1812 * @param options
1813 * options indicating how symbolic links are handled
1814 *
1815 * @return the file attributes
1816 *
1817 * @throws UnsupportedOperationException
1818 * if an attributes of the given type are not supported
1819 * @throws IOException
1820 * if an I/O error occurs
1821 * @throws SecurityException
1822 * In the case of the default provider, a security manager is
1823 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1824 * method is invoked to check read access to the file. If this
1825 * method is invoked to read security sensitive attributes then the
1826 * security manager may be invoke to check for additional permissions.
1827 */
1828 public static <A extends BasicFileAttributes> A readAttributes(Path path,
1829 Class<A> type,
1830 LinkOption... options)
1831 throws IOException
1832 {
1833 return provider(path).readAttributes(path, type, options);
1834 }
1835
1836 /**
1837 * Sets the value of a file attribute.
1838 *
1839 * <p> The {@code attribute} parameter identifies the attribute to be set
1840 * and takes the form:
1841 * <blockquote>
1842 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
1843 * </blockquote>
1844 * where square brackets [...] delineate an optional component and the
1845 * character {@code ':'} stands for itself.
1846 *
1847 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1848 * FileAttributeView} that identifies a set of file attributes. If not
1849 * specified then it defaults to {@code "basic"}, the name of the file
1850 * attribute view that identifies the basic set of file attributes common to
1851 * many file systems. <i>attribute-name</i> is the name of the attribute
1852 * within the set.
1853 *
1854 * <p> The {@code options} array may be used to indicate how symbolic links
1855 * are handled for the case that the file is a symbolic link. By default,
1856 * symbolic links are followed and the file attribute of the final target
1857 * of the link is set. If the option {@link LinkOption#NOFOLLOW_LINKS
1858 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1859 *
1860 * <p> <b>Usage Example:</b>
1861 * Suppose we want to set the DOS "hidden" attribute:
1862 * <pre>
1863 * Path path = ...
1864 * Files.setAttribute(path, "dos:hidden", true);
1865 * </pre>
1866 *
1867 * @param path
1868 * the path to the file
1869 * @param attribute
1870 * the attribute to set
1871 * @param value
1872 * the attribute value
1873 * @param options
1874 * options indicating how symbolic links are handled
1875 *
1876 * @return the given path
1877 *
1878 * @throws UnsupportedOperationException
1879 * if the attribute view is not available
1880 * @throws IllegalArgumentException
1881 * if the attribute name is not specified, or is not recognized, or
1882 * the attribute value is of the correct type but has an
1883 * inappropriate value
1884 * @throws ClassCastException
1885 * if the attribute value is not of the expected type or is a
1886 * collection containing elements that are not of the expected
1887 * type
1888 * @throws IOException
1889 * if an I/O error occurs
1890 * @throws SecurityException
1891 * In the case of the default provider, and a security manager is
1892 * installed, its {@link SecurityManager#checkWrite(String) checkWrite}
1893 * method denies write access to the file. If this method is invoked
1894 * to set security sensitive attributes then the security manager
1895 * may be invoked to check for additional permissions.
1896 */
1897 public static Path setAttribute(Path path, String attribute, Object value,
1898 LinkOption... options)
1899 throws IOException
1900 {
1901 provider(path).setAttribute(path, attribute, value, options);
1902 return path;
1903 }
1904
1905 /**
1906 * Reads the value of a file attribute.
1907 *
1908 * <p> The {@code attribute} parameter identifies the attribute to be read
1909 * and takes the form:
1910 * <blockquote>
1911 * [<i>view-name</i><b>:</b>]<i>attribute-name</i>
1912 * </blockquote>
1913 * where square brackets [...] delineate an optional component and the
1914 * character {@code ':'} stands for itself.
1915 *
1916 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1917 * FileAttributeView} that identifies a set of file attributes. If not
1918 * specified then it defaults to {@code "basic"}, the name of the file
1919 * attribute view that identifies the basic set of file attributes common to
1920 * many file systems. <i>attribute-name</i> is the name of the attribute.
1921 *
1922 * <p> The {@code options} array may be used to indicate how symbolic links
1923 * are handled for the case that the file is a symbolic link. By default,
1924 * symbolic links are followed and the file attribute of the final target
1925 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
1926 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
1927 *
1928 * <p> <b>Usage Example:</b>
1929 * Suppose we require the user ID of the file owner on a system that
1930 * supports a "{@code unix}" view:
1931 * <pre>
1932 * Path path = ...
1933 * int uid = (Integer)Files.getAttribute(path, "unix:uid");
1934 * </pre>
1935 *
1936 * @param path
1937 * the path to the file
1938 * @param attribute
1939 * the attribute to read
1940 * @param options
1941 * options indicating how symbolic links are handled
1942 *
1943 * @return the attribute value
1944 *
1945 * @throws UnsupportedOperationException
1946 * if the attribute view is not available
1947 * @throws IllegalArgumentException
1948 * if the attribute name is not specified or is not recognized
1949 * @throws IOException
1950 * if an I/O error occurs
1951 * @throws SecurityException
1952 * In the case of the default provider, and a security manager is
1953 * installed, its {@link SecurityManager#checkRead(String) checkRead}
1954 * method denies read access to the file. If this method is invoked
1955 * to read security sensitive attributes then the security manager
1956 * may be invoked to check for additional permissions.
1957 */
1958 public static Object getAttribute(Path path, String attribute,
1959 LinkOption... options)
1960 throws IOException
1961 {
1962 // only one attribute should be read
1963 if (attribute.indexOf('*') >= 0 || attribute.indexOf(',') >= 0)
1964 throw new IllegalArgumentException(attribute);
1965 Map<String,Object> map = readAttributes(path, attribute, options);
1966 assert map.size() == 1;
1967 String name;
1968 int pos = attribute.indexOf(':');
1969 if (pos == -1) {
1970 name = attribute;
1971 } else {
1972 name = (pos == attribute.length()) ? "" : attribute.substring(pos+1);
1973 }
1974 return map.get(name);
1975 }
1976
1977 /**
1978 * Reads a set of file attributes as a bulk operation.
1979 *
1980 * <p> The {@code attributes} parameter identifies the attributes to be read
1981 * and takes the form:
1982 * <blockquote>
1983 * [<i>view-name</i><b>:</b>]<i>attribute-list</i>
1984 * </blockquote>
1985 * where square brackets [...] delineate an optional component and the
1986 * character {@code ':'} stands for itself.
1987 *
1988 * <p> <i>view-name</i> is the {@link FileAttributeView#name name} of a {@link
1989 * FileAttributeView} that identifies a set of file attributes. If not
1990 * specified then it defaults to {@code "basic"}, the name of the file
1991 * attribute view that identifies the basic set of file attributes common to
1992 * many file systems.
1993 *
1994 * <p> The <i>attribute-list</i> component is a comma separated list of
1995 * one or more names of attributes to read. If the list contains the value
1996 * {@code "*"} then all attributes are read. Attributes that are not supported
1997 * are ignored and will not be present in the returned map. It is
1998 * implementation specific if all attributes are read as an atomic operation
1999 * with respect to other file system operations.
2000 *
2001 * <p> The following examples demonstrate possible values for the {@code
2002 * attributes} parameter:
2003 *
2004 * <table class="striped" style="text-align: left; margin-left:2em">
2005 * <caption style="display:none">Possible values</caption>
2006 * <thead>
2007 * <tr>
2008 * <th scope="col">Example
2009 * <th scope="col">Description
2010 * </thead>
2011 * <tbody>
2012 * <tr>
2013 * <th scope="row"> {@code "*"} </th>
2014 * <td> Read all {@link BasicFileAttributes basic-file-attributes}. </td>
2015 * </tr>
2016 * <tr>
2017 * <th scope="row"> {@code "size,lastModifiedTime,lastAccessTime"} </th>
2018 * <td> Reads the file size, last modified time, and last access time
2019 * attributes. </td>
2020 * </tr>
2021 * <tr>
2022 * <th scope="row"> {@code "posix:*"} </th>
2023 * <td> Read all {@link PosixFileAttributes POSIX-file-attributes}. </td>
2024 * </tr>
2025 * <tr>
2026 * <th scope="row"> {@code "posix:permissions,owner,size"} </th>
2027 * <td> Reads the POSIX file permissions, owner, and file size. </td>
2028 * </tr>
2029 * </tbody>
2030 * </table>
2031 *
2032 * <p> The {@code options} array may be used to indicate how symbolic links
2033 * are handled for the case that the file is a symbolic link. By default,
2034 * symbolic links are followed and the file attribute of the final target
2035 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2036 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2037 *
2038 * @param path
2039 * the path to the file
2040 * @param attributes
2041 * the attributes to read
2042 * @param options
2043 * options indicating how symbolic links are handled
2044 *
2045 * @return a map of the attributes returned; The map's keys are the
2046 * attribute names, its values are the attribute values
2047 *
2048 * @throws UnsupportedOperationException
2049 * if the attribute view is not available
2050 * @throws IllegalArgumentException
2051 * if no attributes are specified or an unrecognized attribute is
2052 * specified
2053 * @throws IOException
2054 * if an I/O error occurs
2055 * @throws SecurityException
2056 * In the case of the default provider, and a security manager is
2057 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2058 * method denies read access to the file. If this method is invoked
2059 * to read security sensitive attributes then the security manager
2060 * may be invoke to check for additional permissions.
2061 */
2062 public static Map<String,Object> readAttributes(Path path, String attributes,
2063 LinkOption... options)
2064 throws IOException
2065 {
2066 return provider(path).readAttributes(path, attributes, options);
2067 }
2068
2069 /**
2070 * Returns a file's POSIX file permissions.
2071 *
2072 * <p> The {@code path} parameter is associated with a {@code FileSystem}
2073 * that supports the {@link PosixFileAttributeView}. This attribute view
2074 * provides access to file attributes commonly associated with files on file
2075 * systems used by operating systems that implement the Portable Operating
2076 * System Interface (POSIX) family of standards.
2077 *
2078 * <p> The {@code options} array may be used to indicate how symbolic links
2079 * are handled for the case that the file is a symbolic link. By default,
2080 * symbolic links are followed and the file attribute of the final target
2081 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2082 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2083 *
2084 * @param path
2085 * the path to the file
2086 * @param options
2087 * options indicating how symbolic links are handled
2088 *
2089 * @return the file permissions
2090 *
2091 * @throws UnsupportedOperationException
2092 * if the associated file system does not support the {@code
2093 * PosixFileAttributeView}
2094 * @throws IOException
2095 * if an I/O error occurs
2096 * @throws SecurityException
2097 * In the case of the default provider, a security manager is
2098 * installed, and it denies
2099 * {@link RuntimePermission}{@code ("accessUserInformation")}
2100 * or its {@link SecurityManager#checkRead(String) checkRead} method
2101 * denies read access to the file.
2102 */
2103 public static Set<PosixFilePermission> getPosixFilePermissions(Path path,
2104 LinkOption... options)
2105 throws IOException
2106 {
2107 return readAttributes(path, PosixFileAttributes.class, options).permissions();
2108 }
2109
2110 /**
2111 * Sets a file's POSIX permissions.
2112 *
2113 * <p> The {@code path} parameter is associated with a {@code FileSystem}
2114 * that supports the {@link PosixFileAttributeView}. This attribute view
2115 * provides access to file attributes commonly associated with files on file
2116 * systems used by operating systems that implement the Portable Operating
2117 * System Interface (POSIX) family of standards.
2118 *
2119 * @param path
2120 * The path to the file
2121 * @param perms
2122 * The new set of permissions
2123 *
2124 * @return The given path
2125 *
2126 * @throws UnsupportedOperationException
2127 * if the associated file system does not support the {@code
2128 * PosixFileAttributeView}
2129 * @throws ClassCastException
2130 * if the sets contains elements that are not of type {@code
2131 * PosixFilePermission}
2132 * @throws IOException
2133 * if an I/O error occurs
2134 * @throws SecurityException
2135 * In the case of the default provider, and a security manager is
2136 * installed, it denies
2137 * {@link RuntimePermission}{@code ("accessUserInformation")}
2138 * or its {@link SecurityManager#checkWrite(String) checkWrite}
2139 * method denies write access to the file.
2140 */
2141 public static Path setPosixFilePermissions(Path path,
2142 Set<PosixFilePermission> perms)
2143 throws IOException
2144 {
2145 PosixFileAttributeView view =
2146 getFileAttributeView(path, PosixFileAttributeView.class);
2147 if (view == null)
2148 throw new UnsupportedOperationException();
2149 view.setPermissions(perms);
2150 return path;
2151 }
2152
2153 /**
2154 * Returns the owner of a file.
2155 *
2156 * <p> The {@code path} parameter is associated with a file system that
2157 * supports {@link FileOwnerAttributeView}. This file attribute view provides
2158 * access to a file attribute that is the owner of the file.
2159 *
2160 * @param path
2161 * The path to the file
2162 * @param options
2163 * options indicating how symbolic links are handled
2164 *
2165 * @return A user principal representing the owner of the file
2166 *
2167 * @throws UnsupportedOperationException
2168 * if the associated file system does not support the {@code
2169 * FileOwnerAttributeView}
2170 * @throws IOException
2171 * if an I/O error occurs
2172 * @throws SecurityException
2173 * In the case of the default provider, and a security manager is
2174 * installed, it denies
2175 * {@link RuntimePermission}{@code ("accessUserInformation")}
2176 * or its {@link SecurityManager#checkRead(String) checkRead} method
2177 * denies read access to the file.
2178 */
2179 public static UserPrincipal getOwner(Path path, LinkOption... options) throws IOException {
2180 FileOwnerAttributeView view =
2181 getFileAttributeView(path, FileOwnerAttributeView.class, options);
2182 if (view == null)
2183 throw new UnsupportedOperationException();
2184 return view.getOwner();
2185 }
2186
2187 /**
2188 * Updates the file owner.
2189 *
2190 * <p> The {@code path} parameter is associated with a file system that
2191 * supports {@link FileOwnerAttributeView}. This file attribute view provides
2192 * access to a file attribute that is the owner of the file.
2193 *
2194 * <p> <b>Usage Example:</b>
2195 * Suppose we want to make "joe" the owner of a file:
2196 * <pre>
2197 * Path path = ...
2198 * UserPrincipalLookupService lookupService =
2199 * provider(path).getUserPrincipalLookupService();
2200 * UserPrincipal joe = lookupService.lookupPrincipalByName("joe");
2201 * Files.setOwner(path, joe);
2202 * </pre>
2203 *
2204 * @param path
2205 * The path to the file
2206 * @param owner
2207 * The new file owner
2208 *
2209 * @return The given path
2210 *
2211 * @throws UnsupportedOperationException
2212 * if the associated file system does not support the {@code
2213 * FileOwnerAttributeView}
2214 * @throws IOException
2215 * if an I/O error occurs
2216 * @throws SecurityException
2217 * In the case of the default provider, and a security manager is
2218 * installed, it denies
2219 * {@link RuntimePermission}{@code ("accessUserInformation")}
2220 * or its {@link SecurityManager#checkWrite(String) checkWrite}
2221 * method denies write access to the file.
2222 *
2223 * @see FileSystem#getUserPrincipalLookupService
2224 * @see java.nio.file.attribute.UserPrincipalLookupService
2225 */
2226 public static Path setOwner(Path path, UserPrincipal owner)
2227 throws IOException
2228 {
2229 FileOwnerAttributeView view =
2230 getFileAttributeView(path, FileOwnerAttributeView.class);
2231 if (view == null)
2232 throw new UnsupportedOperationException();
2233 view.setOwner(owner);
2234 return path;
2235 }
2236
2237 /**
2238 * Tests whether a file is a symbolic link.
2239 *
2240 * <p> Where it is required to distinguish an I/O exception from the case
2241 * that the file is not a symbolic link then the file attributes can be
2242 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2243 * readAttributes} method and the file type tested with the {@link
2244 * BasicFileAttributes#isSymbolicLink} method.
2245 *
2246 * @param path The path to the file
2247 *
2248 * @return {@code true} if the file is a symbolic link; {@code false} if
2249 * the file does not exist, is not a symbolic link, or it cannot
2250 * be determined if the file is a symbolic link or not.
2251 *
2252 * @throws SecurityException
2253 * In the case of the default provider, and a security manager is
2254 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2255 * method denies read access to the file.
2256 */
2257 public static boolean isSymbolicLink(Path path) {
2258 try {
2259 return readAttributes(path,
2260 BasicFileAttributes.class,
2261 LinkOption.NOFOLLOW_LINKS).isSymbolicLink();
2262 } catch (IOException ioe) {
2263 return false;
2264 }
2265 }
2266
2267 /**
2268 * Tests whether a file is a directory.
2269 *
2270 * <p> The {@code options} array may be used to indicate how symbolic links
2271 * are handled for the case that the file is a symbolic link. By default,
2272 * symbolic links are followed and the file attribute of the final target
2273 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2274 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2275 *
2276 * <p> Where it is required to distinguish an I/O exception from the case
2277 * that the file is not a directory then the file attributes can be
2278 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2279 * readAttributes} method and the file type tested with the {@link
2280 * BasicFileAttributes#isDirectory} method.
2281 *
2282 * @param path
2283 * the path to the file to test
2284 * @param options
2285 * options indicating how symbolic links are handled
2286 *
2287 * @return {@code true} if the file is a directory; {@code false} if
2288 * the file does not exist, is not a directory, or it cannot
2289 * be determined if the file is a directory or not.
2290 *
2291 * @throws SecurityException
2292 * In the case of the default provider, and a security manager is
2293 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2294 * method denies read access to the file.
2295 */
2296 public static boolean isDirectory(Path path, LinkOption... options) {
2297 if (options.length == 0) {
2298 FileSystemProvider provider = provider(path);
2299 if (provider instanceof AbstractFileSystemProvider)
2300 return ((AbstractFileSystemProvider)provider).isDirectory(path);
2301 }
2302
2303 try {
2304 return readAttributes(path, BasicFileAttributes.class, options).isDirectory();
2305 } catch (IOException ioe) {
2306 return false;
2307 }
2308 }
2309
2310 /**
2311 * Tests whether a file is a regular file with opaque content.
2312 *
2313 * <p> The {@code options} array may be used to indicate how symbolic links
2314 * are handled for the case that the file is a symbolic link. By default,
2315 * symbolic links are followed and the file attribute of the final target
2316 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2317 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2318 *
2319 * <p> Where it is required to distinguish an I/O exception from the case
2320 * that the file is not a regular file then the file attributes can be
2321 * read with the {@link #readAttributes(Path,Class,LinkOption[])
2322 * readAttributes} method and the file type tested with the {@link
2323 * BasicFileAttributes#isRegularFile} method.
2324 *
2325 * @param path
2326 * the path to the file
2327 * @param options
2328 * options indicating how symbolic links are handled
2329 *
2330 * @return {@code true} if the file is a regular file; {@code false} if
2331 * the file does not exist, is not a regular file, or it
2332 * cannot be determined if the file is a regular file or not.
2333 *
2334 * @throws SecurityException
2335 * In the case of the default provider, and a security manager is
2336 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2337 * method denies read access to the file.
2338 */
2339 public static boolean isRegularFile(Path path, LinkOption... options) {
2340 if (options.length == 0) {
2341 FileSystemProvider provider = provider(path);
2342 if (provider instanceof AbstractFileSystemProvider)
2343 return ((AbstractFileSystemProvider)provider).isRegularFile(path);
2344 }
2345
2346 try {
2347 return readAttributes(path, BasicFileAttributes.class, options).isRegularFile();
2348 } catch (IOException ioe) {
2349 return false;
2350 }
2351 }
2352
2353 /**
2354 * Returns a file's last modified time.
2355 *
2356 * <p> The {@code options} array may be used to indicate how symbolic links
2357 * are handled for the case that the file is a symbolic link. By default,
2358 * symbolic links are followed and the file attribute of the final target
2359 * of the link is read. If the option {@link LinkOption#NOFOLLOW_LINKS
2360 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2361 *
2362 * @param path
2363 * the path to the file
2364 * @param options
2365 * options indicating how symbolic links are handled
2366 *
2367 * @return a {@code FileTime} representing the time the file was last
2368 * modified, or an implementation specific default when a time
2369 * stamp to indicate the time of last modification is not supported
2370 * by the file system
2371 *
2372 * @throws IOException
2373 * if an I/O error occurs
2374 * @throws SecurityException
2375 * In the case of the default provider, and a security manager is
2376 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2377 * method denies read access to the file.
2378 *
2379 * @see BasicFileAttributes#lastModifiedTime
2380 */
2381 public static FileTime getLastModifiedTime(Path path, LinkOption... options)
2382 throws IOException
2383 {
2384 return readAttributes(path, BasicFileAttributes.class, options).lastModifiedTime();
2385 }
2386
2387 /**
2388 * Updates a file's last modified time attribute. The file time is converted
2389 * to the epoch and precision supported by the file system. Converting from
2390 * finer to coarser granularities result in precision loss. The behavior of
2391 * this method when attempting to set the last modified time when it is not
2392 * supported by the file system or is outside the range supported by the
2393 * underlying file store is not defined. It may or not fail by throwing an
2394 * {@code IOException}.
2395 *
2396 * <p> <b>Usage Example:</b>
2397 * Suppose we want to set the last modified time to the current time:
2398 * <pre>
2399 * Path path = ...
2400 * FileTime now = FileTime.fromMillis(System.currentTimeMillis());
2401 * Files.setLastModifiedTime(path, now);
2402 * </pre>
2403 *
2404 * @param path
2405 * the path to the file
2406 * @param time
2407 * the new last modified time
2408 *
2409 * @return the given path
2410 *
2411 * @throws IOException
2412 * if an I/O error occurs
2413 * @throws SecurityException
2414 * In the case of the default provider, and a security manager is
2415 * installed, its {@link SecurityManager#checkWrite(String)
2416 * checkWrite} method denies write access to the file.
2417 *
2418 * @see BasicFileAttributeView#setTimes
2419 */
2420 public static Path setLastModifiedTime(Path path, FileTime time)
2421 throws IOException
2422 {
2423 getFileAttributeView(path, BasicFileAttributeView.class)
2424 .setTimes(Objects.requireNonNull(time), null, null);
2425 return path;
2426 }
2427
2428 /**
2429 * Returns the size of a file (in bytes). The size may differ from the
2430 * actual size on the file system due to compression, support for sparse
2431 * files, or other reasons. The size of files that are not {@link
2432 * #isRegularFile regular} files is implementation specific and
2433 * therefore unspecified.
2434 *
2435 * @param path
2436 * the path to the file
2437 *
2438 * @return the file size, in bytes
2439 *
2440 * @throws IOException
2441 * if an I/O error occurs
2442 * @throws SecurityException
2443 * In the case of the default provider, and a security manager is
2444 * installed, its {@link SecurityManager#checkRead(String) checkRead}
2445 * method denies read access to the file.
2446 *
2447 * @see BasicFileAttributes#size
2448 */
2449 public static long size(Path path) throws IOException {
2450 return readAttributes(path, BasicFileAttributes.class).size();
2451 }
2452
2453 // -- Accessibility --
2454
2455 /**
2456 * Returns {@code false} if NOFOLLOW_LINKS is present.
2457 */
2458 private static boolean followLinks(LinkOption... options) {
2459 boolean followLinks = true;
2460 for (LinkOption opt: options) {
2461 if (opt == LinkOption.NOFOLLOW_LINKS) {
2462 followLinks = false;
2463 continue;
2464 }
2465 if (opt == null)
2466 throw new NullPointerException();
2467 throw new AssertionError("Should not get here");
2468 }
2469 return followLinks;
2470 }
2471
2472 /**
2473 * Tests whether a file exists.
2474 *
2475 * <p> The {@code options} parameter may be used to indicate how symbolic links
2476 * are handled for the case that the file is a symbolic link. By default,
2477 * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
2478 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2479 *
2480 * <p> Note that the result of this method is immediately outdated. If this
2481 * method indicates the file exists then there is no guarantee that a
2482 * subsequent access will succeed. Care should be taken when using this
2483 * method in security sensitive applications.
2484 *
2485 * @param path
2486 * the path to the file to test
2487 * @param options
2488 * options indicating how symbolic links are handled
2489 * .
2490 * @return {@code true} if the file exists; {@code false} if the file does
2491 * not exist or its existence cannot be determined.
2492 *
2493 * @throws SecurityException
2494 * In the case of the default provider, the {@link
2495 * SecurityManager#checkRead(String)} is invoked to check
2496 * read access to the file.
2497 *
2498 * @see #notExists
2499 */
2500 public static boolean exists(Path path, LinkOption... options) {
2501 if (options.length == 0) {
2502 FileSystemProvider provider = provider(path);
2503 if (provider instanceof AbstractFileSystemProvider)
2504 return ((AbstractFileSystemProvider)provider).exists(path);
2505 }
2506
2507 try {
2508 if (followLinks(options)) {
2509 provider(path).checkAccess(path);
2510 } else {
2511 // attempt to read attributes without following links
2512 readAttributes(path, BasicFileAttributes.class,
2513 LinkOption.NOFOLLOW_LINKS);
2514 }
2515 // file exists
2516 return true;
2517 } catch (IOException x) {
2518 // does not exist or unable to determine if file exists
2519 return false;
2520 }
2521
2522 }
2523
2524 /**
2525 * Tests whether the file located by this path does not exist. This method
2526 * is intended for cases where it is required to take action when it can be
2527 * confirmed that a file does not exist.
2528 *
2529 * <p> The {@code options} parameter may be used to indicate how symbolic links
2530 * are handled for the case that the file is a symbolic link. By default,
2531 * symbolic links are followed. If the option {@link LinkOption#NOFOLLOW_LINKS
2532 * NOFOLLOW_LINKS} is present then symbolic links are not followed.
2533 *
2534 * <p> Note that this method is not the complement of the {@link #exists
2535 * exists} method. Where it is not possible to determine if a file exists
2536 * or not then both methods return {@code false}. As with the {@code exists}
2537 * method, the result of this method is immediately outdated. If this
2538 * method indicates the file does exist then there is no guarantee that a
2539 * subsequent attempt to create the file will succeed. Care should be taken
2540 * when using this method in security sensitive applications.
2541 *
2542 * @param path
2543 * the path to the file to test
2544 * @param options
2545 * options indicating how symbolic links are handled
2546 *
2547 * @return {@code true} if the file does not exist; {@code false} if the
2548 * file exists or its existence cannot be determined
2549 *
2550 * @throws SecurityException
2551 * In the case of the default provider, the {@link
2552 * SecurityManager#checkRead(String)} is invoked to check
2553 * read access to the file.
2554 */
2555 public static boolean notExists(Path path, LinkOption... options) {
2556 try {
2557 if (followLinks(options)) {
2558 provider(path).checkAccess(path);
2559 } else {
2560 // attempt to read attributes without following links
2561 readAttributes(path, BasicFileAttributes.class,
2562 LinkOption.NOFOLLOW_LINKS);
2563 }
2564 // file exists
2565 return false;
2566 } catch (NoSuchFileException x) {
2567 // file confirmed not to exist
2568 return true;
2569 } catch (IOException x) {
2570 return false;
2571 }
2572 }
2573
2574 /**
2575 * Used by isReadable, isWritable, isExecutable to test access to a file.
2576 */
2577 private static boolean isAccessible(Path path, AccessMode... modes) {
2578 try {
2579 provider(path).checkAccess(path, modes);
2580 return true;
2581 } catch (IOException x) {
2582 return false;
2583 }
2584 }
2585
2586 /**
2587 * Tests whether a file is readable. This method checks that a file exists
2588 * and that this Java virtual machine has appropriate privileges that would
2589 * allow it open the file for reading. Depending on the implementation, this
2590 * method may require to read file permissions, access control lists, or
2591 * other file attributes in order to check the effective access to the file.
2592 * Consequently, this method may not be atomic with respect to other file
2593 * system operations.
2594 *
2595 * <p> Note that the result of this method is immediately outdated, there is
2596 * no guarantee that a subsequent attempt to open the file for reading will
2597 * succeed (or even that it will access the same file). Care should be taken
2598 * when using this method in security sensitive applications.
2599 *
2600 * @param path
2601 * the path to the file to check
2602 *
2603 * @return {@code true} if the file exists and is readable; {@code false}
2604 * if the file does not exist, read access would be denied because
2605 * the Java virtual machine has insufficient privileges, or access
2606 * cannot be determined
2607 *
2608 * @throws SecurityException
2609 * In the case of the default provider, and a security manager is
2610 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2611 * is invoked to check read access to the file.
2612 */
2613 public static boolean isReadable(Path path) {
2614 return isAccessible(path, AccessMode.READ);
2615 }
2616
2617 /**
2618 * Tests whether a file is writable. This method checks that a file exists
2619 * and that this Java virtual machine has appropriate privileges that would
2620 * allow it open the file for writing. Depending on the implementation, this
2621 * method may require to read file permissions, access control lists, or
2622 * other file attributes in order to check the effective access to the file.
2623 * Consequently, this method may not be atomic with respect to other file
2624 * system operations.
2625 *
2626 * <p> Note that result of this method is immediately outdated, there is no
2627 * guarantee that a subsequent attempt to open the file for writing will
2628 * succeed (or even that it will access the same file). Care should be taken
2629 * when using this method in security sensitive applications.
2630 *
2631 * @param path
2632 * the path to the file to check
2633 *
2634 * @return {@code true} if the file exists and is writable; {@code false}
2635 * if the file does not exist, write access would be denied because
2636 * the Java virtual machine has insufficient privileges, or access
2637 * cannot be determined
2638 *
2639 * @throws SecurityException
2640 * In the case of the default provider, and a security manager is
2641 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2642 * is invoked to check write access to the file.
2643 */
2644 public static boolean isWritable(Path path) {
2645 return isAccessible(path, AccessMode.WRITE);
2646 }
2647
2648 /**
2649 * Tests whether a file is executable. This method checks that a file exists
2650 * and that this Java virtual machine has appropriate privileges to {@link
2651 * Runtime#exec execute} the file. The semantics may differ when checking
2652 * access to a directory. For example, on UNIX systems, checking for
2653 * execute access checks that the Java virtual machine has permission to
2654 * search the directory in order to access file or subdirectories.
2655 *
2656 * <p> Depending on the implementation, this method may require to read file
2657 * permissions, access control lists, or other file attributes in order to
2658 * check the effective access to the file. Consequently, this method may not
2659 * be atomic with respect to other file system operations.
2660 *
2661 * <p> Note that the result of this method is immediately outdated, there is
2662 * no guarantee that a subsequent attempt to execute the file will succeed
2663 * (or even that it will access the same file). Care should be taken when
2664 * using this method in security sensitive applications.
2665 *
2666 * @param path
2667 * the path to the file to check
2668 *
2669 * @return {@code true} if the file exists and is executable; {@code false}
2670 * if the file does not exist, execute access would be denied because
2671 * the Java virtual machine has insufficient privileges, or access
2672 * cannot be determined
2673 *
2674 * @throws SecurityException
2675 * In the case of the default provider, and a security manager is
2676 * installed, the {@link SecurityManager#checkExec(String)
2677 * checkExec} is invoked to check execute access to the file.
2678 */
2679 public static boolean isExecutable(Path path) {
2680 return isAccessible(path, AccessMode.EXECUTE);
2681 }
2682
2683 // -- Recursive operations --
2684
2685 /**
2686 * Walks a file tree.
2687 *
2688 * <p> This method walks a file tree rooted at a given starting file. The
2689 * file tree traversal is <em>depth-first</em> with the given {@link
2690 * FileVisitor} invoked for each file encountered. File tree traversal
2691 * completes when all accessible files in the tree have been visited, or a
2692 * visit method returns a result of {@link FileVisitResult#TERMINATE
2693 * TERMINATE}. Where a visit method terminates due an {@code IOException},
2694 * an uncaught error, or runtime exception, then the traversal is terminated
2695 * and the error or exception is propagated to the caller of this method.
2696 *
2697 * <p> For each file encountered this method attempts to read its {@link
2698 * java.nio.file.attribute.BasicFileAttributes}. If the file is not a
2699 * directory then the {@link FileVisitor#visitFile visitFile} method is
2700 * invoked with the file attributes. If the file attributes cannot be read,
2701 * due to an I/O exception, then the {@link FileVisitor#visitFileFailed
2702 * visitFileFailed} method is invoked with the I/O exception.
2703 *
2704 * <p> Where the file is a directory, and the directory could not be opened,
2705 * then the {@code visitFileFailed} method is invoked with the I/O exception,
2706 * after which, the file tree walk continues, by default, at the next
2707 * <em>sibling</em> of the directory.
2708 *
2709 * <p> Where the directory is opened successfully, then the entries in the
2710 * directory, and their <em>descendants</em> are visited. When all entries
2711 * have been visited, or an I/O error occurs during iteration of the
2712 * directory, then the directory is closed and the visitor's {@link
2713 * FileVisitor#postVisitDirectory postVisitDirectory} method is invoked.
2714 * The file tree walk then continues, by default, at the next <em>sibling</em>
2715 * of the directory.
2716 *
2717 * <p> By default, symbolic links are not automatically followed by this
2718 * method. If the {@code options} parameter contains the {@link
2719 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then symbolic links are
2720 * followed. When following links, and the attributes of the target cannot
2721 * be read, then this method attempts to get the {@code BasicFileAttributes}
2722 * of the link. If they can be read then the {@code visitFile} method is
2723 * invoked with the attributes of the link (otherwise the {@code visitFileFailed}
2724 * method is invoked as specified above).
2725 *
2726 * <p> If the {@code options} parameter contains the {@link
2727 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then this method keeps
2728 * track of directories visited so that cycles can be detected. A cycle
2729 * arises when there is an entry in a directory that is an ancestor of the
2730 * directory. Cycle detection is done by recording the {@link
2731 * java.nio.file.attribute.BasicFileAttributes#fileKey file-key} of directories,
2732 * or if file keys are not available, by invoking the {@link #isSameFile
2733 * isSameFile} method to test if a directory is the same file as an
2734 * ancestor. When a cycle is detected it is treated as an I/O error, and the
2735 * {@link FileVisitor#visitFileFailed visitFileFailed} method is invoked with
2736 * an instance of {@link FileSystemLoopException}.
2737 *
2738 * <p> The {@code maxDepth} parameter is the maximum number of levels of
2739 * directories to visit. A value of {@code 0} means that only the starting
2740 * file is visited, unless denied by the security manager. A value of
2741 * {@link Integer#MAX_VALUE MAX_VALUE} may be used to indicate that all
2742 * levels should be visited. The {@code visitFile} method is invoked for all
2743 * files, including directories, encountered at {@code maxDepth}, unless the
2744 * basic file attributes cannot be read, in which case the {@code
2745 * visitFileFailed} method is invoked.
2746 *
2747 * <p> If a visitor returns a result of {@code null} then {@code
2748 * NullPointerException} is thrown.
2749 *
2750 * <p> When a security manager is installed and it denies access to a file
2751 * (or directory), then it is ignored and the visitor is not invoked for
2752 * that file (or directory).
2753 *
2754 * @param start
2755 * the starting file
2756 * @param options
2757 * options to configure the traversal
2758 * @param maxDepth
2759 * the maximum number of directory levels to visit
2760 * @param visitor
2761 * the file visitor to invoke for each file
2762 *
2763 * @return the starting file
2764 *
2765 * @throws IllegalArgumentException
2766 * if the {@code maxDepth} parameter is negative
2767 * @throws SecurityException
2768 * If the security manager denies access to the starting file.
2769 * In the case of the default provider, the {@link
2770 * SecurityManager#checkRead(String) checkRead} method is invoked
2771 * to check read access to the directory.
2772 * @throws IOException
2773 * if an I/O error is thrown by a visitor method
2774 */
2775 public static Path walkFileTree(Path start,
2776 Set<FileVisitOption> options,
2777 int maxDepth,
2778 FileVisitor<? super Path> visitor)
2779 throws IOException
2780 {
2781 /**
2782 * Create a FileTreeWalker to walk the file tree, invoking the visitor
2783 * for each event.
2784 */
2785 try (FileTreeWalker walker = new FileTreeWalker(options, maxDepth)) {
2786 FileTreeWalker.Event ev = walker.walk(start);
2787 do {
2788 FileVisitResult result;
2789 switch (ev.type()) {
2790 case ENTRY :
2791 IOException ioe = ev.ioeException();
2792 if (ioe == null) {
2793 assert ev.attributes() != null;
2794 result = visitor.visitFile(ev.file(), ev.attributes());
2795 } else {
2796 result = visitor.visitFileFailed(ev.file(), ioe);
2797 }
2798 break;
2799
2800 case START_DIRECTORY :
2801 result = visitor.preVisitDirectory(ev.file(), ev.attributes());
2802
2803 // if SKIP_SIBLINGS and SKIP_SUBTREE is returned then
2804 // there shouldn't be any more events for the current
2805 // directory.
2806 if (result == FileVisitResult.SKIP_SUBTREE ||
2807 result == FileVisitResult.SKIP_SIBLINGS)
2808 walker.pop();
2809 break;
2810
2811 case END_DIRECTORY :
2812 result = visitor.postVisitDirectory(ev.file(), ev.ioeException());
2813
2814 // SKIP_SIBLINGS is a no-op for postVisitDirectory
2815 if (result == FileVisitResult.SKIP_SIBLINGS)
2816 result = FileVisitResult.CONTINUE;
2817 break;
2818
2819 default :
2820 throw new AssertionError("Should not get here");
2821 }
2822
2823 if (Objects.requireNonNull(result) != FileVisitResult.CONTINUE) {
2824 if (result == FileVisitResult.TERMINATE) {
2825 break;
2826 } else if (result == FileVisitResult.SKIP_SIBLINGS) {
2827 walker.skipRemainingSiblings();
2828 }
2829 }
2830 ev = walker.next();
2831 } while (ev != null);
2832 }
2833
2834 return start;
2835 }
2836
2837 /**
2838 * Walks a file tree.
2839 *
2840 * <p> This method works as if invoking it were equivalent to evaluating the
2841 * expression:
2842 * <blockquote><pre>
2843 * walkFileTree(start, EnumSet.noneOf(FileVisitOption.class), Integer.MAX_VALUE, visitor)
2844 * </pre></blockquote>
2845 * In other words, it does not follow symbolic links, and visits all levels
2846 * of the file tree.
2847 *
2848 * @param start
2849 * the starting file
2850 * @param visitor
2851 * the file visitor to invoke for each file
2852 *
2853 * @return the starting file
2854 *
2855 * @throws SecurityException
2856 * If the security manager denies access to the starting file.
2857 * In the case of the default provider, the {@link
2858 * SecurityManager#checkRead(String) checkRead} method is invoked
2859 * to check read access to the directory.
2860 * @throws IOException
2861 * if an I/O error is thrown by a visitor method
2862 */
2863 public static Path walkFileTree(Path start, FileVisitor<? super Path> visitor)
2864 throws IOException
2865 {
2866 return walkFileTree(start,
2867 EnumSet.noneOf(FileVisitOption.class),
2868 Integer.MAX_VALUE,
2869 visitor);
2870 }
2871
2872
2873 // -- Utility methods for simple usages --
2874
2875 // buffer size used for reading and writing
2876 private static final int BUFFER_SIZE = 8192;
2877
2878 /**
2879 * Opens a file for reading, returning a {@code BufferedReader} that may be
2880 * used to read text from the file in an efficient manner. Bytes from the
2881 * file are decoded into characters using the specified charset. Reading
2882 * commences at the beginning of the file.
2883 *
2884 * <p> The {@code Reader} methods that read from the file throw {@code
2885 * IOException} if a malformed or unmappable byte sequence is read.
2886 *
2887 * @param path
2888 * the path to the file
2889 * @param cs
2890 * the charset to use for decoding
2891 *
2892 * @return a new buffered reader, with default buffer size, to read text
2893 * from the file
2894 *
2895 * @throws IOException
2896 * if an I/O error occurs opening the file
2897 * @throws SecurityException
2898 * In the case of the default provider, and a security manager is
2899 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2900 * method is invoked to check read access to the file.
2901 *
2902 * @see #readAllLines
2903 */
2904 public static BufferedReader newBufferedReader(Path path, Charset cs)
2905 throws IOException
2906 {
2907 CharsetDecoder decoder = cs.newDecoder();
2908 Reader reader = new InputStreamReader(newInputStream(path), decoder);
2909 return new BufferedReader(reader);
2910 }
2911
2912 /**
2913 * Opens a file for reading, returning a {@code BufferedReader} to read text
2914 * from the file in an efficient manner. Bytes from the file are decoded into
2915 * characters using the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset
2916 * charset}.
2917 *
2918 * <p> This method works as if invoking it were equivalent to evaluating the
2919 * expression:
2920 * <pre>{@code
2921 * Files.newBufferedReader(path, StandardCharsets.UTF_8)
2922 * }</pre>
2923 *
2924 * @param path
2925 * the path to the file
2926 *
2927 * @return a new buffered reader, with default buffer size, to read text
2928 * from the file
2929 *
2930 * @throws IOException
2931 * if an I/O error occurs opening the file
2932 * @throws SecurityException
2933 * In the case of the default provider, and a security manager is
2934 * installed, the {@link SecurityManager#checkRead(String) checkRead}
2935 * method is invoked to check read access to the file.
2936 *
2937 * @since 1.8
2938 */
2939 public static BufferedReader newBufferedReader(Path path) throws IOException {
2940 return newBufferedReader(path, StandardCharsets.UTF_8);
2941 }
2942
2943 /**
2944 * Opens or creates a file for writing, returning a {@code BufferedWriter}
2945 * that may be used to write text to the file in an efficient manner.
2946 * The {@code options} parameter specifies how the file is created or
2947 * opened. If no options are present then this method works as if the {@link
2948 * StandardOpenOption#CREATE CREATE}, {@link
2949 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
2950 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
2951 * opens the file for writing, creating the file if it doesn't exist, or
2952 * initially truncating an existing {@link #isRegularFile regular-file} to
2953 * a size of {@code 0} if it exists.
2954 *
2955 * <p> The {@code Writer} methods to write text throw {@code IOException}
2956 * if the text cannot be encoded using the specified charset.
2957 *
2958 * @param path
2959 * the path to the file
2960 * @param cs
2961 * the charset to use for encoding
2962 * @param options
2963 * options specifying how the file is opened
2964 *
2965 * @return a new buffered writer, with default buffer size, to write text
2966 * to the file
2967 *
2968 * @throws IllegalArgumentException
2969 * if {@code options} contains an invalid combination of options
2970 * @throws IOException
2971 * if an I/O error occurs opening or creating the file
2972 * @throws UnsupportedOperationException
2973 * if an unsupported option is specified
2974 * @throws SecurityException
2975 * In the case of the default provider, and a security manager is
2976 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
2977 * method is invoked to check write access to the file. The {@link
2978 * SecurityManager#checkDelete(String) checkDelete} method is
2979 * invoked to check delete access if the file is opened with the
2980 * {@code DELETE_ON_CLOSE} option.
2981 *
2982 * @see #write(Path,Iterable,Charset,OpenOption[])
2983 */
2984 public static BufferedWriter newBufferedWriter(Path path, Charset cs,
2985 OpenOption... options)
2986 throws IOException
2987 {
2988 CharsetEncoder encoder = cs.newEncoder();
2989 Writer writer = new OutputStreamWriter(newOutputStream(path, options), encoder);
2990 return new BufferedWriter(writer);
2991 }
2992
2993 /**
2994 * Opens or creates a file for writing, returning a {@code BufferedWriter}
2995 * to write text to the file in an efficient manner. The text is encoded
2996 * into bytes for writing using the {@link StandardCharsets#UTF_8 UTF-8}
2997 * {@link Charset charset}.
2998 *
2999 * <p> This method works as if invoking it were equivalent to evaluating the
3000 * expression:
3001 * <pre>{@code
3002 * Files.newBufferedWriter(path, StandardCharsets.UTF_8, options)
3003 * }</pre>
3004 *
3005 * @param path
3006 * the path to the file
3007 * @param options
3008 * options specifying how the file is opened
3009 *
3010 * @return a new buffered writer, with default buffer size, to write text
3011 * to the file
3012 *
3013 * @throws IllegalArgumentException
3014 * if {@code options} contains an invalid combination of options
3015 * @throws IOException
3016 * if an I/O error occurs opening or creating the file
3017 * @throws UnsupportedOperationException
3018 * if an unsupported option is specified
3019 * @throws SecurityException
3020 * In the case of the default provider, and a security manager is
3021 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3022 * method is invoked to check write access to the file. The {@link
3023 * SecurityManager#checkDelete(String) checkDelete} method is
3024 * invoked to check delete access if the file is opened with the
3025 * {@code DELETE_ON_CLOSE} option.
3026 *
3027 * @since 1.8
3028 */
3029 public static BufferedWriter newBufferedWriter(Path path, OpenOption... options)
3030 throws IOException
3031 {
3032 return newBufferedWriter(path, StandardCharsets.UTF_8, options);
3033 }
3034
3035 /**
3036 * Copies all bytes from an input stream to a file. On return, the input
3037 * stream will be at end of stream.
3038 *
3039 * <p> By default, the copy fails if the target file already exists or is a
3040 * symbolic link. If the {@link StandardCopyOption#REPLACE_EXISTING
3041 * REPLACE_EXISTING} option is specified, and the target file already exists,
3042 * then it is replaced if it is not a non-empty directory. If the target
3043 * file exists and is a symbolic link, then the symbolic link is replaced.
3044 * In this release, the {@code REPLACE_EXISTING} option is the only option
3045 * required to be supported by this method. Additional options may be
3046 * supported in future releases.
3047 *
3048 * <p> If an I/O error occurs reading from the input stream or writing to
3049 * the file, then it may do so after the target file has been created and
3050 * after some bytes have been read or written. Consequently the input
3051 * stream may not be at end of stream and may be in an inconsistent state.
3052 * It is strongly recommended that the input stream be promptly closed if an
3053 * I/O error occurs.
3054 *
3055 * <p> This method may block indefinitely reading from the input stream (or
3056 * writing to the file). The behavior for the case that the input stream is
3057 * <i>asynchronously closed</i> or the thread interrupted during the copy is
3058 * highly input stream and file system provider specific and therefore not
3059 * specified.
3060 *
3061 * <p> <b>Usage example</b>: Suppose we want to capture a web page and save
3062 * it to a file:
3063 * <pre>
3064 * Path path = ...
3065 * URI u = URI.create("http://java.sun.com/");
3066 * try (InputStream in = u.toURL().openStream()) {
3067 * Files.copy(in, path);
3068 * }
3069 * </pre>
3070 *
3071 * @param in
3072 * the input stream to read from
3073 * @param target
3074 * the path to the file
3075 * @param options
3076 * options specifying how the copy should be done
3077 *
3078 * @return the number of bytes read or written
3079 *
3080 * @throws IOException
3081 * if an I/O error occurs when reading or writing
3082 * @throws FileAlreadyExistsException
3083 * if the target file exists but cannot be replaced because the
3084 * {@code REPLACE_EXISTING} option is not specified <i>(optional
3085 * specific exception)</i>
3086 * @throws DirectoryNotEmptyException
3087 * the {@code REPLACE_EXISTING} option is specified but the file
3088 * cannot be replaced because it is a non-empty directory
3089 * <i>(optional specific exception)</i> *
3090 * @throws UnsupportedOperationException
3091 * if {@code options} contains a copy option that is not supported
3092 * @throws SecurityException
3093 * In the case of the default provider, and a security manager is
3094 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3095 * method is invoked to check write access to the file. Where the
3096 * {@code REPLACE_EXISTING} option is specified, the security
3097 * manager's {@link SecurityManager#checkDelete(String) checkDelete}
3098 * method is invoked to check that an existing file can be deleted.
3099 */
3100 public static long copy(InputStream in, Path target, CopyOption... options)
3101 throws IOException
3102 {
3103 // ensure not null before opening file
3104 Objects.requireNonNull(in);
3105
3106 // check for REPLACE_EXISTING
3107 boolean replaceExisting = false;
3108 for (CopyOption opt: options) {
3109 if (opt == StandardCopyOption.REPLACE_EXISTING) {
3110 replaceExisting = true;
3111 } else {
3112 if (opt == null) {
3113 throw new NullPointerException("options contains 'null'");
3114 } else {
3115 throw new UnsupportedOperationException(opt + " not supported");
3116 }
3117 }
3118 }
3119
3120 // attempt to delete an existing file
3121 SecurityException se = null;
3122 if (replaceExisting) {
3123 try {
3124 deleteIfExists(target);
3125 } catch (SecurityException x) {
3126 se = x;
3127 }
3128 }
3129
3130 // attempt to create target file. If it fails with
3131 // FileAlreadyExistsException then it may be because the security
3132 // manager prevented us from deleting the file, in which case we just
3133 // throw the SecurityException.
3134 OutputStream ostream;
3135 try {
3136 ostream = newOutputStream(target, StandardOpenOption.CREATE_NEW,
3137 StandardOpenOption.WRITE);
3138 } catch (FileAlreadyExistsException x) {
3139 if (se != null)
3140 throw se;
3141 // someone else won the race and created the file
3142 throw x;
3143 }
3144
3145 // do the copy
3146 try (OutputStream out = ostream) {
3147 return in.transferTo(out);
3148 }
3149 }
3150
3151 /**
3152 * Copies all bytes from a file to an output stream.
3153 *
3154 * <p> If an I/O error occurs reading from the file or writing to the output
3155 * stream, then it may do so after some bytes have been read or written.
3156 * Consequently the output stream may be in an inconsistent state. It is
3157 * strongly recommended that the output stream be promptly closed if an I/O
3158 * error occurs.
3159 *
3160 * <p> This method may block indefinitely writing to the output stream (or
3161 * reading from the file). The behavior for the case that the output stream
3162 * is <i>asynchronously closed</i> or the thread interrupted during the copy
3163 * is highly output stream and file system provider specific and therefore
3164 * not specified.
3165 *
3166 * <p> Note that if the given output stream is {@link java.io.Flushable}
3167 * then its {@link java.io.Flushable#flush flush} method may need to invoked
3168 * after this method completes so as to flush any buffered output.
3169 *
3170 * @param source
3171 * the path to the file
3172 * @param out
3173 * the output stream to write to
3174 *
3175 * @return the number of bytes read or written
3176 *
3177 * @throws IOException
3178 * if an I/O error occurs when reading or writing
3179 * @throws SecurityException
3180 * In the case of the default provider, and a security manager is
3181 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3182 * method is invoked to check read access to the file.
3183 */
3184 public static long copy(Path source, OutputStream out) throws IOException {
3185 // ensure not null before opening file
3186 Objects.requireNonNull(out);
3187
3188 try (InputStream in = newInputStream(source)) {
3189 return in.transferTo(out);
3190 }
3191 }
3192
3193 /**
3194 * The maximum size of array to allocate.
3195 * Some VMs reserve some header words in an array.
3196 * Attempts to allocate larger arrays may result in
3197 * OutOfMemoryError: Requested array size exceeds VM limit
3198 */
3199 private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
3200
3201 /**
3202 * Reads all the bytes from an input stream. Uses {@code initialSize} as a hint
3203 * about how many bytes the stream will have.
3204 *
3205 * @param source
3206 * the input stream to read from
3207 * @param initialSize
3208 * the initial size of the byte array to allocate
3209 *
3210 * @return a byte array containing the bytes read from the file
3211 *
3212 * @throws IOException
3213 * if an I/O error occurs reading from the stream
3214 * @throws OutOfMemoryError
3215 * if an array of the required size cannot be allocated
3216 */
3217 private static byte[] read(InputStream source, int initialSize) throws IOException {
3218 int capacity = initialSize;
3219 byte[] buf = new byte[capacity];
3220 int nread = 0;
3221 int n;
3222 for (;;) {
3223 // read to EOF which may read more or less than initialSize (eg: file
3224 // is truncated while we are reading)
3225 while ((n = source.read(buf, nread, capacity - nread)) > 0)
3226 nread += n;
3227
3228 // if last call to source.read() returned -1, we are done
3229 // otherwise, try to read one more byte; if that failed we're done too
3230 if (n < 0 || (n = source.read()) < 0)
3231 break;
3232
3233 // one more byte was read; need to allocate a larger buffer
3234 if (capacity <= MAX_BUFFER_SIZE - capacity) {
3235 capacity = Math.max(capacity << 1, BUFFER_SIZE);
3236 } else {
3237 if (capacity == MAX_BUFFER_SIZE)
3238 throw new OutOfMemoryError("Required array size too large");
3239 capacity = MAX_BUFFER_SIZE;
3240 }
3241 buf = Arrays.copyOf(buf, capacity);
3242 buf[nread++] = (byte)n;
3243 }
3244 return (capacity == nread) ? buf : Arrays.copyOf(buf, nread);
3245 }
3246
3247 /**
3248 * Reads all the bytes from a file. The method ensures that the file is
3249 * closed when all bytes have been read or an I/O error, or other runtime
3250 * exception, is thrown.
3251 *
3252 * <p> Note that this method is intended for simple cases where it is
3253 * convenient to read all bytes into a byte array. It is not intended for
3254 * reading in large files.
3255 *
3256 * @param path
3257 * the path to the file
3258 *
3259 * @return a byte array containing the bytes read from the file
3260 *
3261 * @throws IOException
3262 * if an I/O error occurs reading from the stream
3263 * @throws OutOfMemoryError
3264 * if an array of the required size cannot be allocated, for
3265 * example the file is larger that {@code 2GB}
3266 * @throws SecurityException
3267 * In the case of the default provider, and a security manager is
3268 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3269 * method is invoked to check read access to the file.
3270 */
3271 public static byte[] readAllBytes(Path path) throws IOException {
3272 try (SeekableByteChannel sbc = Files.newByteChannel(path);
3273 InputStream in = Channels.newInputStream(sbc)) {
3274 long size = sbc.size();
3275 if (size > (long)MAX_BUFFER_SIZE)
3276 throw new OutOfMemoryError("Required array size too large");
3277
3278 return read(in, (int)size);
3279 }
3280 }
3281
3282 /**
3283 * Read all lines from a file. This method ensures that the file is
3284 * closed when all bytes have been read or an I/O error, or other runtime
3285 * exception, is thrown. Bytes from the file are decoded into characters
3286 * using the specified charset.
3287 *
3288 * <p> This method recognizes the following as line terminators:
3289 * <ul>
3290 * <li> <code>\u000D</code> followed by <code>\u000A</code>,
3291 * CARRIAGE RETURN followed by LINE FEED </li>
3292 * <li> <code>\u000A</code>, LINE FEED </li>
3293 * <li> <code>\u000D</code>, CARRIAGE RETURN </li>
3294 * </ul>
3295 * <p> Additional Unicode line terminators may be recognized in future
3296 * releases.
3297 *
3298 * <p> Note that this method is intended for simple cases where it is
3299 * convenient to read all lines in a single operation. It is not intended
3300 * for reading in large files.
3301 *
3302 * @param path
3303 * the path to the file
3304 * @param cs
3305 * the charset to use for decoding
3306 *
3307 * @return the lines from the file as a {@code List}; whether the {@code
3308 * List} is modifiable or not is implementation dependent and
3309 * therefore not specified
3310 *
3311 * @throws IOException
3312 * if an I/O error occurs reading from the file or a malformed or
3313 * unmappable byte sequence is read
3314 * @throws SecurityException
3315 * In the case of the default provider, and a security manager is
3316 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3317 * method is invoked to check read access to the file.
3318 *
3319 * @see #newBufferedReader
3320 */
3321 public static List<String> readAllLines(Path path, Charset cs) throws IOException {
3322 try (BufferedReader reader = newBufferedReader(path, cs)) {
3323 List<String> result = new ArrayList<>();
3324 for (;;) {
3325 String line = reader.readLine();
3326 if (line == null)
3327 break;
3328 result.add(line);
3329 }
3330 return result;
3331 }
3332 }
3333
3334 /**
3335 * Read all lines from a file. Bytes from the file are decoded into characters
3336 * using the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
3337 *
3338 * <p> This method works as if invoking it were equivalent to evaluating the
3339 * expression:
3340 * <pre>{@code
3341 * Files.readAllLines(path, StandardCharsets.UTF_8)
3342 * }</pre>
3343 *
3344 * @param path
3345 * the path to the file
3346 *
3347 * @return the lines from the file as a {@code List}; whether the {@code
3348 * List} is modifiable or not is implementation dependent and
3349 * therefore not specified
3350 *
3351 * @throws IOException
3352 * if an I/O error occurs reading from the file or a malformed or
3353 * unmappable byte sequence is read
3354 * @throws SecurityException
3355 * In the case of the default provider, and a security manager is
3356 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3357 * method is invoked to check read access to the file.
3358 *
3359 * @since 1.8
3360 */
3361 public static List<String> readAllLines(Path path) throws IOException {
3362 return readAllLines(path, StandardCharsets.UTF_8);
3363 }
3364
3365 /**
3366 * Writes bytes to a file. The {@code options} parameter specifies how
3367 * the file is created or opened. If no options are present then this method
3368 * works as if the {@link StandardOpenOption#CREATE CREATE}, {@link
3369 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3370 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3371 * opens the file for writing, creating the file if it doesn't exist, or
3372 * initially truncating an existing {@link #isRegularFile regular-file} to
3373 * a size of {@code 0}. All bytes in the byte array are written to the file.
3374 * The method ensures that the file is closed when all bytes have been
3375 * written (or an I/O error or other runtime exception is thrown). If an I/O
3376 * error occurs then it may do so after the file has been created or
3377 * truncated, or after some bytes have been written to the file.
3378 *
3379 * <p> <b>Usage example</b>: By default the method creates a new file or
3380 * overwrites an existing file. Suppose you instead want to append bytes
3381 * to an existing file:
3382 * <pre>
3383 * Path path = ...
3384 * byte[] bytes = ...
3385 * Files.write(path, bytes, StandardOpenOption.APPEND);
3386 * </pre>
3387 *
3388 * @param path
3389 * the path to the file
3390 * @param bytes
3391 * the byte array with the bytes to write
3392 * @param options
3393 * options specifying how the file is opened
3394 *
3395 * @return the path
3396 *
3397 * @throws IllegalArgumentException
3398 * if {@code options} contains an invalid combination of options
3399 * @throws IOException
3400 * if an I/O error occurs writing to or creating the file
3401 * @throws UnsupportedOperationException
3402 * if an unsupported option is specified
3403 * @throws SecurityException
3404 * In the case of the default provider, and a security manager is
3405 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3406 * method is invoked to check write access to the file. The {@link
3407 * SecurityManager#checkDelete(String) checkDelete} method is
3408 * invoked to check delete access if the file is opened with the
3409 * {@code DELETE_ON_CLOSE} option.
3410 */
3411 public static Path write(Path path, byte[] bytes, OpenOption... options)
3412 throws IOException
3413 {
3414 // ensure bytes is not null before opening file
3415 Objects.requireNonNull(bytes);
3416
3417 try (OutputStream out = Files.newOutputStream(path, options)) {
3418 int len = bytes.length;
3419 int rem = len;
3420 while (rem > 0) {
3421 int n = Math.min(rem, BUFFER_SIZE);
3422 out.write(bytes, (len-rem), n);
3423 rem -= n;
3424 }
3425 }
3426 return path;
3427 }
3428
3429 /**
3430 * Write lines of text to a file. Each line is a char sequence and is
3431 * written to the file in sequence with each line terminated by the
3432 * platform's line separator, as defined by the system property {@code
3433 * line.separator}. Characters are encoded into bytes using the specified
3434 * charset.
3435 *
3436 * <p> The {@code options} parameter specifies how the file is created
3437 * or opened. If no options are present then this method works as if the
3438 * {@link StandardOpenOption#CREATE CREATE}, {@link
3439 * StandardOpenOption#TRUNCATE_EXISTING TRUNCATE_EXISTING}, and {@link
3440 * StandardOpenOption#WRITE WRITE} options are present. In other words, it
3441 * opens the file for writing, creating the file if it doesn't exist, or
3442 * initially truncating an existing {@link #isRegularFile regular-file} to
3443 * a size of {@code 0}. The method ensures that the file is closed when all
3444 * lines have been written (or an I/O error or other runtime exception is
3445 * thrown). If an I/O error occurs then it may do so after the file has
3446 * been created or truncated, or after some bytes have been written to the
3447 * file.
3448 *
3449 * @param path
3450 * the path to the file
3451 * @param lines
3452 * an object to iterate over the char sequences
3453 * @param cs
3454 * the charset to use for encoding
3455 * @param options
3456 * options specifying how the file is opened
3457 *
3458 * @return the path
3459 *
3460 * @throws IllegalArgumentException
3461 * if {@code options} contains an invalid combination of options
3462 * @throws IOException
3463 * if an I/O error occurs writing to or creating the file, or the
3464 * text cannot be encoded using the specified charset
3465 * @throws UnsupportedOperationException
3466 * if an unsupported option is specified
3467 * @throws SecurityException
3468 * In the case of the default provider, and a security manager is
3469 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3470 * method is invoked to check write access to the file. The {@link
3471 * SecurityManager#checkDelete(String) checkDelete} method is
3472 * invoked to check delete access if the file is opened with the
3473 * {@code DELETE_ON_CLOSE} option.
3474 */
3475 public static Path write(Path path, Iterable<? extends CharSequence> lines,
3476 Charset cs, OpenOption... options)
3477 throws IOException
3478 {
3479 // ensure lines is not null before opening file
3480 Objects.requireNonNull(lines);
3481 CharsetEncoder encoder = cs.newEncoder();
3482 OutputStream out = newOutputStream(path, options);
3483 try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out, encoder))) {
3484 for (CharSequence line: lines) {
3485 writer.append(line);
3486 writer.newLine();
3487 }
3488 }
3489 return path;
3490 }
3491
3492 /**
3493 * Write lines of text to a file. Characters are encoded into bytes using
3494 * the {@link StandardCharsets#UTF_8 UTF-8} {@link Charset charset}.
3495 *
3496 * <p> This method works as if invoking it were equivalent to evaluating the
3497 * expression:
3498 * <pre>{@code
3499 * Files.write(path, lines, StandardCharsets.UTF_8, options);
3500 * }</pre>
3501 *
3502 * @param path
3503 * the path to the file
3504 * @param lines
3505 * an object to iterate over the char sequences
3506 * @param options
3507 * options specifying how the file is opened
3508 *
3509 * @return the path
3510 *
3511 * @throws IllegalArgumentException
3512 * if {@code options} contains an invalid combination of options
3513 * @throws IOException
3514 * if an I/O error occurs writing to or creating the file, or the
3515 * text cannot be encoded as {@code UTF-8}
3516 * @throws UnsupportedOperationException
3517 * if an unsupported option is specified
3518 * @throws SecurityException
3519 * In the case of the default provider, and a security manager is
3520 * installed, the {@link SecurityManager#checkWrite(String) checkWrite}
3521 * method is invoked to check write access to the file. The {@link
3522 * SecurityManager#checkDelete(String) checkDelete} method is
3523 * invoked to check delete access if the file is opened with the
3524 * {@code DELETE_ON_CLOSE} option.
3525 *
3526 * @since 1.8
3527 */
3528 public static Path write(Path path,
3529 Iterable<? extends CharSequence> lines,
3530 OpenOption... options)
3531 throws IOException
3532 {
3533 return write(path, lines, StandardCharsets.UTF_8, options);
3534 }
3535
3536 // -- Stream APIs --
3537
3538 /**
3539 * Return a lazily populated {@code Stream}, the elements of
3540 * which are the entries in the directory. The listing is not recursive.
3541 *
3542 * <p> The elements of the stream are {@link Path} objects that are
3543 * obtained as if by {@link Path#resolve(Path) resolving} the name of the
3544 * directory entry against {@code dir}. Some file systems maintain special
3545 * links to the directory itself and the directory's parent directory.
3546 * Entries representing these links are not included.
3547 *
3548 * <p> The stream is <i>weakly consistent</i>. It is thread safe but does
3549 * not freeze the directory while iterating, so it may (or may not)
3550 * reflect updates to the directory that occur after returning from this
3551 * method.
3552 *
3553 * <p> The returned stream contains a reference to an open directory.
3554 * The directory is closed by closing the stream.
3555 *
3556 * <p> Operating on a closed stream behaves as if the end of stream
3557 * has been reached. Due to read-ahead, one or more elements may be
3558 * returned after the stream has been closed.
3559 *
3560 * <p> If an {@link IOException} is thrown when accessing the directory
3561 * after this method has returned, it is wrapped in an {@link
3562 * UncheckedIOException} which will be thrown from the method that caused
3563 * the access to take place.
3564 *
3565 * @apiNote
3566 * This method must be used within a try-with-resources statement or similar
3567 * control structure to ensure that the stream's open directory is closed
3568 * promptly after the stream's operations have completed.
3569 *
3570 * @param dir The path to the directory
3571 *
3572 * @return The {@code Stream} describing the content of the
3573 * directory
3574 *
3575 * @throws NotDirectoryException
3576 * if the file could not otherwise be opened because it is not
3577 * a directory <i>(optional specific exception)</i>
3578 * @throws IOException
3579 * if an I/O error occurs when opening the directory
3580 * @throws SecurityException
3581 * In the case of the default provider, and a security manager is
3582 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3583 * method is invoked to check read access to the directory.
3584 *
3585 * @see #newDirectoryStream(Path)
3586 * @since 1.8
3587 */
3588 public static Stream<Path> list(Path dir) throws IOException {
3589 DirectoryStream<Path> ds = Files.newDirectoryStream(dir);
3590 try {
3591 final Iterator<Path> delegate = ds.iterator();
3592
3593 // Re-wrap DirectoryIteratorException to UncheckedIOException
3594 Iterator<Path> iterator = new Iterator<>() {
3595 @Override
3596 public boolean hasNext() {
3597 try {
3598 return delegate.hasNext();
3599 } catch (DirectoryIteratorException e) {
3600 throw new UncheckedIOException(e.getCause());
3601 }
3602 }
3603 @Override
3604 public Path next() {
3605 try {
3606 return delegate.next();
3607 } catch (DirectoryIteratorException e) {
3608 throw new UncheckedIOException(e.getCause());
3609 }
3610 }
3611 };
3612
3613 Spliterator<Path> spliterator =
3614 Spliterators.spliteratorUnknownSize(iterator, Spliterator.DISTINCT);
3615 return StreamSupport.stream(spliterator, false)
3616 .onClose(asUncheckedRunnable(ds));
3617 } catch (Error|RuntimeException e) {
3618 try {
3619 ds.close();
3620 } catch (IOException ex) {
3621 try {
3622 e.addSuppressed(ex);
3623 } catch (Throwable ignore) {}
3624 }
3625 throw e;
3626 }
3627 }
3628
3629 /**
3630 * Return a {@code Stream} that is lazily populated with {@code
3631 * Path} by walking the file tree rooted at a given starting file. The
3632 * file tree is traversed <em>depth-first</em>, the elements in the stream
3633 * are {@link Path} objects that are obtained as if by {@link
3634 * Path#resolve(Path) resolving} the relative path against {@code start}.
3635 *
3636 * <p> The {@code stream} walks the file tree as elements are consumed.
3637 * The {@code Stream} returned is guaranteed to have at least one
3638 * element, the starting file itself. For each file visited, the stream
3639 * attempts to read its {@link BasicFileAttributes}. If the file is a
3640 * directory and can be opened successfully, entries in the directory, and
3641 * their <em>descendants</em> will follow the directory in the stream as
3642 * they are encountered. When all entries have been visited, then the
3643 * directory is closed. The file tree walk then continues at the next
3644 * <em>sibling</em> of the directory.
3645 *
3646 * <p> The stream is <i>weakly consistent</i>. It does not freeze the
3647 * file tree while iterating, so it may (or may not) reflect updates to
3648 * the file tree that occur after returned from this method.
3649 *
3650 * <p> By default, symbolic links are not automatically followed by this
3651 * method. If the {@code options} parameter contains the {@link
3652 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then symbolic links are
3653 * followed. When following links, and the attributes of the target cannot
3654 * be read, then this method attempts to get the {@code BasicFileAttributes}
3655 * of the link.
3656 *
3657 * <p> If the {@code options} parameter contains the {@link
3658 * FileVisitOption#FOLLOW_LINKS FOLLOW_LINKS} option then the stream keeps
3659 * track of directories visited so that cycles can be detected. A cycle
3660 * arises when there is an entry in a directory that is an ancestor of the
3661 * directory. Cycle detection is done by recording the {@link
3662 * java.nio.file.attribute.BasicFileAttributes#fileKey file-key} of directories,
3663 * or if file keys are not available, by invoking the {@link #isSameFile
3664 * isSameFile} method to test if a directory is the same file as an
3665 * ancestor. When a cycle is detected it is treated as an I/O error with
3666 * an instance of {@link FileSystemLoopException}.
3667 *
3668 * <p> The {@code maxDepth} parameter is the maximum number of levels of
3669 * directories to visit. A value of {@code 0} means that only the starting
3670 * file is visited, unless denied by the security manager. A value of
3671 * {@link Integer#MAX_VALUE MAX_VALUE} may be used to indicate that all
3672 * levels should be visited.
3673 *
3674 * <p> When a security manager is installed and it denies access to a file
3675 * (or directory), then it is ignored and not included in the stream.
3676 *
3677 * <p> The returned stream contains references to one or more open directories.
3678 * The directories are closed by closing the stream.
3679 *
3680 * <p> If an {@link IOException} is thrown when accessing the directory
3681 * after this method has returned, it is wrapped in an {@link
3682 * UncheckedIOException} which will be thrown from the method that caused
3683 * the access to take place.
3684 *
3685 * @apiNote
3686 * This method must be used within a try-with-resources statement or similar
3687 * control structure to ensure that the stream's open directories are closed
3688 * promptly after the stream's operations have completed.
3689 *
3690 * @param start
3691 * the starting file
3692 * @param maxDepth
3693 * the maximum number of directory levels to visit
3694 * @param options
3695 * options to configure the traversal
3696 *
3697 * @return the {@link Stream} of {@link Path}
3698 *
3699 * @throws IllegalArgumentException
3700 * if the {@code maxDepth} parameter is negative
3701 * @throws SecurityException
3702 * If the security manager denies access to the starting file.
3703 * In the case of the default provider, the {@link
3704 * SecurityManager#checkRead(String) checkRead} method is invoked
3705 * to check read access to the directory.
3706 * @throws IOException
3707 * if an I/O error is thrown when accessing the starting file.
3708 * @since 1.8
3709 */
3710 public static Stream<Path> walk(Path start,
3711 int maxDepth,
3712 FileVisitOption... options)
3713 throws IOException
3714 {
3715 FileTreeIterator iterator = new FileTreeIterator(start, maxDepth, options);
3716 try {
3717 Spliterator<FileTreeWalker.Event> spliterator =
3718 Spliterators.spliteratorUnknownSize(iterator, Spliterator.DISTINCT);
3719 return StreamSupport.stream(spliterator, false)
3720 .onClose(iterator::close)
3721 .map(entry -> entry.file());
3722 } catch (Error|RuntimeException e) {
3723 iterator.close();
3724 throw e;
3725 }
3726 }
3727
3728 /**
3729 * Return a {@code Stream} that is lazily populated with {@code
3730 * Path} by walking the file tree rooted at a given starting file. The
3731 * file tree is traversed <em>depth-first</em>, the elements in the stream
3732 * are {@link Path} objects that are obtained as if by {@link
3733 * Path#resolve(Path) resolving} the relative path against {@code start}.
3734 *
3735 * <p> This method works as if invoking it were equivalent to evaluating the
3736 * expression:
3737 * <blockquote><pre>
3738 * walk(start, Integer.MAX_VALUE, options)
3739 * </pre></blockquote>
3740 * In other words, it visits all levels of the file tree.
3741 *
3742 * <p> The returned stream contains references to one or more open directories.
3743 * The directories are closed by closing the stream.
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 directories are closed
3748 * promptly after the stream's operations have completed.
3749 *
3750 * @param start
3751 * the starting file
3752 * @param options
3753 * options to configure the traversal
3754 *
3755 * @return the {@link Stream} of {@link Path}
3756 *
3757 * @throws SecurityException
3758 * If the security manager denies access to the starting file.
3759 * In the case of the default provider, the {@link
3760 * SecurityManager#checkRead(String) checkRead} method is invoked
3761 * to check read access to the directory.
3762 * @throws IOException
3763 * if an I/O error is thrown when accessing the starting file.
3764 *
3765 * @see #walk(Path, int, FileVisitOption...)
3766 * @since 1.8
3767 */
3768 public static Stream<Path> walk(Path start, FileVisitOption... options) throws IOException {
3769 return walk(start, Integer.MAX_VALUE, options);
3770 }
3771
3772 /**
3773 * Return a {@code Stream} that is lazily populated with {@code
3774 * Path} by searching for files in a file tree rooted at a given starting
3775 * file.
3776 *
3777 * <p> This method walks the file tree in exactly the manner specified by
3778 * the {@link #walk walk} method. For each file encountered, the given
3779 * {@link BiPredicate} is invoked with its {@link Path} and {@link
3780 * BasicFileAttributes}. The {@code Path} object is obtained as if by
3781 * {@link Path#resolve(Path) resolving} the relative path against {@code
3782 * start} and is only included in the returned {@link Stream} if
3783 * the {@code BiPredicate} returns true. Compare to calling {@link
3784 * java.util.stream.Stream#filter filter} on the {@code Stream}
3785 * returned by {@code walk} method, this method may be more efficient by
3786 * avoiding redundant retrieval of the {@code BasicFileAttributes}.
3787 *
3788 * <p> The returned stream contains references to one or more open directories.
3789 * The directories are closed by closing the stream.
3790 *
3791 * <p> If an {@link IOException} is thrown when accessing the directory
3792 * after returned from this method, it is wrapped in an {@link
3793 * UncheckedIOException} which will be thrown from the method that caused
3794 * the access to take place.
3795 *
3796 * @apiNote
3797 * This method must be used within a try-with-resources statement or similar
3798 * control structure to ensure that the stream's open directories are closed
3799 * promptly after the stream's operations have completed.
3800 *
3801 * @param start
3802 * the starting file
3803 * @param maxDepth
3804 * the maximum number of directory levels to search
3805 * @param matcher
3806 * the function used to decide whether a file should be included
3807 * in the returned stream
3808 * @param options
3809 * options to configure the traversal
3810 *
3811 * @return the {@link Stream} of {@link Path}
3812 *
3813 * @throws IllegalArgumentException
3814 * if the {@code maxDepth} parameter is negative
3815 * @throws SecurityException
3816 * If the security manager denies access to the starting file.
3817 * In the case of the default provider, the {@link
3818 * SecurityManager#checkRead(String) checkRead} method is invoked
3819 * to check read access to the directory.
3820 * @throws IOException
3821 * if an I/O error is thrown when accessing the starting file.
3822 *
3823 * @see #walk(Path, int, FileVisitOption...)
3824 * @since 1.8
3825 */
3826 public static Stream<Path> find(Path start,
3827 int maxDepth,
3828 BiPredicate<Path, BasicFileAttributes> matcher,
3829 FileVisitOption... options)
3830 throws IOException
3831 {
3832 FileTreeIterator iterator = new FileTreeIterator(start, maxDepth, options);
3833 try {
3834 Spliterator<FileTreeWalker.Event> spliterator =
3835 Spliterators.spliteratorUnknownSize(iterator, Spliterator.DISTINCT);
3836 return StreamSupport.stream(spliterator, false)
3837 .onClose(iterator::close)
3838 .filter(entry -> matcher.test(entry.file(), entry.attributes()))
3839 .map(entry -> entry.file());
3840 } catch (Error|RuntimeException e) {
3841 iterator.close();
3842 throw e;
3843 }
3844 }
3845
3846
3847 /**
3848 * Read all lines from a file as a {@code Stream}. Unlike {@link
3849 * #readAllLines(Path, Charset) readAllLines}, this method does not read
3850 * all lines into a {@code List}, but instead populates lazily as the stream
3851 * is consumed.
3852 *
3853 * <p> Bytes from the file are decoded into characters using the specified
3854 * charset and the same line terminators as specified by {@code
3855 * readAllLines} are supported.
3856 *
3857 * <p> The returned stream contains a reference to an open file. The file
3858 * is closed by closing the stream.
3859 *
3860 * <p> The file contents should not be modified during the execution of the
3861 * terminal stream operation. Otherwise, the result of the terminal stream
3862 * operation is undefined.
3863 *
3864 * <p> After this method returns, then any subsequent I/O exception that
3865 * occurs while reading from the file or when a malformed or unmappable byte
3866 * sequence is read, is wrapped in an {@link UncheckedIOException} that will
3867 * be thrown from the
3868 * {@link java.util.stream.Stream} method that caused the read to take
3869 * place. In case an {@code IOException} is thrown when closing the file,
3870 * it is also wrapped as an {@code UncheckedIOException}.
3871 *
3872 * @apiNote
3873 * This method must be used within a try-with-resources statement or similar
3874 * control structure to ensure that the stream's open file is closed promptly
3875 * after the stream's operations have completed.
3876 *
3877 * @implNote
3878 * This implementation supports good parallel stream performance for the
3879 * standard charsets {@link StandardCharsets#UTF_8 UTF-8},
3880 * {@link StandardCharsets#US_ASCII US-ASCII} and
3881 * {@link StandardCharsets#ISO_8859_1 ISO-8859-1}. Such
3882 * <em>line-optimal</em> charsets have the property that the encoded bytes
3883 * of a line feed ('\n') or a carriage return ('\r') are efficiently
3884 * identifiable from other encoded characters when randomly accessing the
3885 * bytes of the file.
3886 *
3887 * <p> For non-<em>line-optimal</em> charsets the stream source's
3888 * spliterator has poor splitting properties, similar to that of a
3889 * spliterator associated with an iterator or that associated with a stream
3890 * returned from {@link BufferedReader#lines()}. Poor splitting properties
3891 * can result in poor parallel stream performance.
3892 *
3893 * <p> For <em>line-optimal</em> charsets the stream source's spliterator
3894 * has good splitting properties, assuming the file contains a regular
3895 * sequence of lines. Good splitting properties can result in good parallel
3896 * stream performance. The spliterator for a <em>line-optimal</em> charset
3897 * takes advantage of the charset properties (a line feed or a carriage
3898 * return being efficient identifiable) such that when splitting it can
3899 * approximately divide the number of covered lines in half.
3900 *
3901 * @param path
3902 * the path to the file
3903 * @param cs
3904 * the charset to use for decoding
3905 *
3906 * @return the lines from the file as a {@code Stream}
3907 *
3908 * @throws IOException
3909 * if an I/O error occurs opening the file
3910 * @throws SecurityException
3911 * In the case of the default provider, and a security manager is
3912 * installed, the {@link SecurityManager#checkRead(String) checkRead}
3913 * method is invoked to check read access to the file.
3914 *
3915 * @see #readAllLines(Path, Charset)
3916 * @see #newBufferedReader(Path, Charset)
3917 * @see java.io.BufferedReader#lines()
3918 * @since 1.8
3919 */
3920 public static Stream<String> lines(Path path, Charset cs) throws IOException {
3921 // Use the good splitting spliterator if:
3922 // 1) the path is associated with the default file system;
3923 // 2) the character set is supported; and
3924 // 3) the file size is such that all bytes can be indexed by int values
3925 // (this limitation is imposed by ByteBuffer)
3926 if (path.getFileSystem() == FileSystems.getDefault() &&
3927 FileChannelLinesSpliterator.SUPPORTED_CHARSET_NAMES.contains(cs.name())) {
3928 FileChannel fc = FileChannel.open(path, StandardOpenOption.READ);
3929
3930 Stream<String> fcls = createFileChannelLinesStream(fc, cs);
3931 if (fcls != null) {
3932 return fcls;
3933 }
3934 fc.close();
3935 }
3936
3937 return createBufferedReaderLinesStream(Files.newBufferedReader(path, cs));
3938 }
3939
3940 private static Stream<String> createFileChannelLinesStream(FileChannel fc, Charset cs) throws IOException {
3941 try {
3942 // Obtaining the size from the FileChannel is much faster
3943 // than obtaining using path.toFile().length()
3944 long length = fc.size();
3945 // FileChannel.size() may in certain circumstances return zero
3946 // for a non-zero length file so disallow this case.
3947 if (length > 0 && length <= Integer.MAX_VALUE) {
3948 Spliterator<String> s = new FileChannelLinesSpliterator(fc, cs, 0, (int) length);
3949 return StreamSupport.stream(s, false)
3950 .onClose(Files.asUncheckedRunnable(fc));
3951 }
3952 } catch (Error|RuntimeException|IOException e) {
3953 try {
3954 fc.close();
3955 } catch (IOException ex) {
3956 try {
3957 e.addSuppressed(ex);
3958 } catch (Throwable ignore) {
3959 }
3960 }
3961 throw e;
3962 }
3963 return null;
3964 }
3965
3966 private static Stream<String> createBufferedReaderLinesStream(BufferedReader br) {
3967 try {
3968 return br.lines().onClose(asUncheckedRunnable(br));
3969 } catch (Error|RuntimeException e) {
3970 try {
3971 br.close();
3972 } catch (IOException ex) {
3973 try {
3974 e.addSuppressed(ex);
3975 } catch (Throwable ignore) {
3976 }
3977 }
3978 throw e;
3979 }
3980 }
3981
3982 /**
3983 * Read all lines from a file as a {@code Stream}. Bytes from the file are
3984 * decoded into characters using the {@link StandardCharsets#UTF_8 UTF-8}
3985 * {@link Charset charset}.
3986 *
3987 * <p> The returned stream contains a reference to an open file. The file
3988 * is closed by closing the stream.
3989 *
3990 * <p> The file contents should not be modified during the execution of the
3991 * terminal stream operation. Otherwise, the result of the terminal stream
3992 * operation is undefined.
3993 *
3994 * <p> This method works as if invoking it were equivalent to evaluating the
3995 * expression:
3996 * <pre>{@code
3997 * Files.lines(path, StandardCharsets.UTF_8)
3998 * }</pre>
3999 *
4000 * @apiNote
4001 * This method must be used within a try-with-resources statement or similar
4002 * control structure to ensure that the stream's open file is closed promptly
4003 * after the stream's operations have completed.
4004 *
4005 * @param path
4006 * the path to the file
4007 *
4008 * @return the lines from the file as a {@code Stream}
4009 *
4010 * @throws IOException
4011 * if an I/O error occurs opening the file
4012 * @throws SecurityException
4013 * In the case of the default provider, and a security manager is
4014 * installed, the {@link SecurityManager#checkRead(String) checkRead}
4015 * method is invoked to check read access to the file.
4016 *
4017 * @since 1.8
4018 */
4019 public static Stream<String> lines(Path path) throws IOException {
4020 return lines(path, StandardCharsets.UTF_8);
4021 }
4022 }