1 /*
2 * Copyright (c) 2007, 2013, 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
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7 * published by the Free Software Foundation. Oracle designates this
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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).
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24 */
25
26 package java.nio.file;
27
28 import java.io.File;
29 import java.io.IOException;
30 import java.net.URI;
31 import java.util.Iterator;
32 import java.util.NoSuchElementException;
33
34 /**
35 * An object that may be used to locate a file in a file system. It will
36 * typically represent a system dependent file path.
37 *
38 * <p> A {@code Path} represents a path that is hierarchical and composed of a
39 * sequence of directory and file name elements separated by a special separator
40 * or delimiter. A <em>root component</em>, that identifies a file system
41 * hierarchy, may also be present. The name element that is <em>farthest</em>
42 * from the root of the directory hierarchy is the name of a file or directory.
43 * The other name elements are directory names. A {@code Path} can represent a
44 * root, a root and a sequence of names, or simply one or more name elements.
45 * A {@code Path} is considered to be an <i>empty path</i> if it consists
46 * solely of one name element that is empty. Accessing a file using an
47 * <i>empty path</i> is equivalent to accessing the default directory of the
48 * file system. {@code Path} defines the {@link #getFileName() getFileName},
49 * {@link #getParent getParent}, {@link #getRoot getRoot}, and {@link #subpath
50 * subpath} methods to access the path components or a subsequence of its name
51 * elements.
52 *
53 * <p> In addition to accessing the components of a path, a {@code Path} also
54 * defines the {@link #resolve(Path) resolve} and {@link #resolveSibling(Path)
55 * resolveSibling} methods to combine paths. The {@link #relativize relativize}
56 * method that can be used to construct a relative path between two paths.
57 * Paths can be {@link #compareTo compared}, and tested against each other using
58 * the {@link #startsWith startsWith} and {@link #endsWith endsWith} methods.
59 *
60 * <p> This interface extends {@link Watchable} interface so that a directory
61 * located by a path can be {@link #register registered} with a {@link
62 * WatchService} and entries in the directory watched. </p>
63 *
64 * <p> <b>WARNING:</b> This interface is only intended to be implemented by
65 * those developing custom file system implementations. Methods may be added to
66 * this interface in future releases. </p>
67 *
68 * <h2>Accessing Files</h2>
69 * <p> Paths may be used with the {@link Files} class to operate on files,
70 * directories, and other types of files. For example, suppose we want a {@link
71 * java.io.BufferedReader} to read text from a file "{@code access.log}". The
72 * file is located in a directory "{@code logs}" relative to the current working
73 * directory and is UTF-8 encoded.
74 * <pre>
75 * Path path = FileSystems.getDefault().getPath("logs", "access.log");
76 * BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8);
77 * </pre>
78 *
79 * <a name="interop"></a><h2>Interoperability</h2>
80 * <p> Paths associated with the default {@link
81 * java.nio.file.spi.FileSystemProvider provider} are generally interoperable
82 * with the {@link java.io.File java.io.File} class. Paths created by other
83 * providers are unlikely to be interoperable with the abstract path names
84 * represented by {@code java.io.File}. The {@link java.io.File#toPath toPath}
85 * method may be used to obtain a {@code Path} from the abstract path name
86 * represented by a {@code java.io.File} object. The resulting {@code Path} can
87 * be used to operate on the same file as the {@code java.io.File} object. In
88 * addition, the {@link #toFile toFile} method is useful to construct a {@code
89 * File} from the {@code String} representation of a {@code Path}.
90 *
91 * <h2>Concurrency</h2>
92 * <p> Implementations of this interface are immutable and safe for use by
93 * multiple concurrent threads.
94 *
95 * @since 1.7
96 * @see Paths
97 */
98
99 public interface Path
100 extends Comparable<Path>, Iterable<Path>, Watchable
101 {
102 /**
103 * Returns the file system that created this object.
104 *
105 * @return the file system that created this object
106 */
107 FileSystem getFileSystem();
108
109 /**
110 * Tells whether or not this path is absolute.
111 *
112 * <p> An absolute path is complete in that it doesn't need to be combined
113 * with other path information in order to locate a file.
114 *
115 * @return {@code true} if, and only if, this path is absolute
116 */
117 boolean isAbsolute();
118
119 /**
120 * Returns the root component of this path as a {@code Path} object,
121 * or {@code null} if this path does not have a root component.
122 *
123 * @return a path representing the root component of this path,
124 * or {@code null}
125 */
126 Path getRoot();
127
128 /**
129 * Returns the name of the file or directory denoted by this path as a
130 * {@code Path} object. The file name is the <em>farthest</em> element from
131 * the root in the directory hierarchy.
132 *
133 * @return a path representing the name of the file or directory, or
134 * {@code null} if this path has zero elements
135 */
136 Path getFileName();
137
138 /**
139 * Returns the <em>parent path</em>, or {@code null} if this path does not
140 * have a parent.
141 *
142 * <p> The parent of this path object consists of this path's root
143 * component, if any, and each element in the path except for the
144 * <em>farthest</em> from the root in the directory hierarchy. This method
145 * does not access the file system; the path or its parent may not exist.
146 * Furthermore, this method does not eliminate special names such as "."
147 * and ".." that may be used in some implementations. On UNIX for example,
148 * the parent of "{@code /a/b/c}" is "{@code /a/b}", and the parent of
149 * {@code "x/y/.}" is "{@code x/y}". This method may be used with the {@link
150 * #normalize normalize} method, to eliminate redundant names, for cases where
151 * <em>shell-like</em> navigation is required.
152 *
153 * <p> If this path has one or more elements, and no root component, then
154 * this method is equivalent to evaluating the expression:
155 * <blockquote><pre>
156 * subpath(0, getNameCount()-1);
157 * </pre></blockquote>
158 *
159 * @return a path representing the path's parent
160 */
161 Path getParent();
162
163 /**
164 * Returns the number of name elements in the path.
165 *
166 * @return the number of elements in the path, or {@code 0} if this path
167 * only represents a root component
168 */
169 int getNameCount();
170
171 /**
172 * Returns a name element of this path as a {@code Path} object.
173 *
174 * <p> The {@code index} parameter is the index of the name element to return.
175 * The element that is <em>closest</em> to the root in the directory hierarchy
176 * has index {@code 0}. The element that is <em>farthest</em> from the root
177 * has index {@link #getNameCount count}{@code -1}.
178 *
179 * @param index
180 * the index of the element
181 *
182 * @return the name element
183 *
184 * @throws IllegalArgumentException
185 * if {@code index} is negative, {@code index} is greater than or
186 * equal to the number of elements, or this path has zero name
187 * elements
188 */
189 Path getName(int index);
190
191 /**
192 * Returns a relative {@code Path} that is a subsequence of the name
193 * elements of this path.
194 *
195 * <p> The {@code beginIndex} and {@code endIndex} parameters specify the
196 * subsequence of name elements. The name that is <em>closest</em> to the root
197 * in the directory hierarchy has index {@code 0}. The name that is
198 * <em>farthest</em> from the root has index {@link #getNameCount
199 * count}{@code -1}. The returned {@code Path} object has the name elements
200 * that begin at {@code beginIndex} and extend to the element at index {@code
201 * endIndex-1}.
202 *
203 * @param beginIndex
204 * the index of the first element, inclusive
205 * @param endIndex
206 * the index of the last element, exclusive
207 *
208 * @return a new {@code Path} object that is a subsequence of the name
209 * elements in this {@code Path}
210 *
211 * @throws IllegalArgumentException
212 * if {@code beginIndex} is negative, or greater than or equal to
213 * the number of elements. If {@code endIndex} is less than or
214 * equal to {@code beginIndex}, or larger than the number of elements.
215 */
216 Path subpath(int beginIndex, int endIndex);
217
218 /**
219 * Tests if this path starts with the given path.
220 *
221 * <p> This path <em>starts</em> with the given path if this path's root
222 * component <em>starts</em> with the root component of the given path,
223 * and this path starts with the same name elements as the given path.
224 * If the given path has more name elements than this path then {@code false}
225 * is returned.
226 *
227 * <p> Whether or not the root component of this path starts with the root
228 * component of the given path is file system specific. If this path does
229 * not have a root component and the given path has a root component then
230 * this path does not start with the given path.
231 *
232 * <p> If the given path is associated with a different {@code FileSystem}
233 * to this path then {@code false} is returned.
234 *
235 * @param other
236 * the given path
237 *
238 * @return {@code true} if this path starts with the given path; otherwise
239 * {@code false}
240 */
241 boolean startsWith(Path other);
242
243 /**
244 * Tests if this path starts with a {@code Path}, constructed by converting
245 * the given path string, in exactly the manner specified by the {@link
246 * #startsWith(Path) startsWith(Path)} method. On UNIX for example, the path
247 * "{@code foo/bar}" starts with "{@code foo}" and "{@code foo/bar}". It
248 * does not start with "{@code f}" or "{@code fo}".
249 *
250 * @implSpec
251 * The default implementation is equivalent for this path to:
252 * <pre>{@code
253 * startsWith(getFileSystem().getPath(other));
254 * }</pre>
255 *
256 * @param other
257 * the given path string
258 *
259 * @return {@code true} if this path starts with the given path; otherwise
260 * {@code false}
261 *
262 * @throws InvalidPathException
263 * If the path string cannot be converted to a Path.
264 */
265 default boolean startsWith(String other) {
266 return startsWith(getFileSystem().getPath(other));
267 }
268
269 /**
270 * Tests if this path ends with the given path.
271 *
272 * <p> If the given path has <em>N</em> elements, and no root component,
273 * and this path has <em>N</em> or more elements, then this path ends with
274 * the given path if the last <em>N</em> elements of each path, starting at
275 * the element farthest from the root, are equal.
276 *
277 * <p> If the given path has a root component then this path ends with the
278 * given path if the root component of this path <em>ends with</em> the root
279 * component of the given path, and the corresponding elements of both paths
280 * are equal. Whether or not the root component of this path ends with the
281 * root component of the given path is file system specific. If this path
282 * does not have a root component and the given path has a root component
283 * then this path does not end with the given path.
284 *
285 * <p> If the given path is associated with a different {@code FileSystem}
286 * to this path then {@code false} is returned.
287 *
288 * @param other
289 * the given path
290 *
291 * @return {@code true} if this path ends with the given path; otherwise
292 * {@code false}
293 */
294 boolean endsWith(Path other);
295
296 /**
297 * Tests if this path ends with a {@code Path}, constructed by converting
298 * the given path string, in exactly the manner specified by the {@link
299 * #endsWith(Path) endsWith(Path)} method. On UNIX for example, the path
300 * "{@code foo/bar}" ends with "{@code foo/bar}" and "{@code bar}". It does
301 * not end with "{@code r}" or "{@code /bar}". Note that trailing separators
302 * are not taken into account, and so invoking this method on the {@code
303 * Path}"{@code foo/bar}" with the {@code String} "{@code bar/}" returns
304 * {@code true}.
305 *
306 * @implSpec
307 * The default implementation is equivalent for this path to:
308 * <pre>{@code
309 * endsWith(getFileSystem().getPath(other));
310 * }</pre>
311 *
312 * @param other
313 * the given path string
314 *
315 * @return {@code true} if this path ends with the given path; otherwise
316 * {@code false}
317 *
318 * @throws InvalidPathException
319 * If the path string cannot be converted to a Path.
320 */
321 default boolean endsWith(String other) {
322 return endsWith(getFileSystem().getPath(other));
323 }
324
325 /**
326 * Returns a path that is this path with redundant name elements eliminated.
327 *
328 * <p> The precise definition of this method is implementation dependent but
329 * in general it derives from this path, a path that does not contain
330 * <em>redundant</em> name elements. In many file systems, the "{@code .}"
331 * and "{@code ..}" are special names used to indicate the current directory
332 * and parent directory. In such file systems all occurrences of "{@code .}"
333 * are considered redundant. If a "{@code ..}" is preceded by a
334 * non-"{@code ..}" name then both names are considered redundant (the
335 * process to identify such names is repeated until it is no longer
336 * applicable).
337 *
338 * <p> This method does not access the file system; the path may not locate
339 * a file that exists. Eliminating "{@code ..}" and a preceding name from a
340 * path may result in the path that locates a different file than the original
341 * path. This can arise when the preceding name is a symbolic link.
342 *
343 * @return the resulting path or this path if it does not contain
344 * redundant name elements; an empty path is returned if this path
345 * does not have a root component and all name elements are redundant
346 *
347 * @see #getParent
348 * @see #toRealPath
349 */
350 Path normalize();
351
352 // -- resolution and relativization --
353
354 /**
355 * Resolve the given path against this path.
356 *
357 * <p> If the {@code other} parameter is an {@link #isAbsolute() absolute}
358 * path then this method trivially returns {@code other}. If {@code other}
359 * is an <i>empty path</i> then this method trivially returns this path.
360 * Otherwise this method considers this path to be a directory and resolves
361 * the given path against this path. In the simplest case, the given path
362 * does not have a {@link #getRoot root} component, in which case this method
363 * <em>joins</em> the given path to this path and returns a resulting path
364 * that {@link #endsWith ends} with the given path. Where the given path has
365 * a root component then resolution is highly implementation dependent and
366 * therefore unspecified.
367 *
368 * @param other
369 * the path to resolve against this path
370 *
371 * @return the resulting path
372 *
373 * @see #relativize
374 */
375 Path resolve(Path other);
376
377 /**
378 * Converts a given path string to a {@code Path} and resolves it against
379 * this {@code Path} in exactly the manner specified by the {@link
380 * #resolve(Path) resolve} method. For example, suppose that the name
381 * separator is "{@code /}" and a path represents "{@code foo/bar}", then
382 * invoking this method with the path string "{@code gus}" will result in
383 * the {@code Path} "{@code foo/bar/gus}".
384 *
385 * @implSpec
386 * The default implementation is equivalent for this path to:
387 * <pre>{@code
388 * resolve(getFileSystem().getPath(other));
389 * }</pre>
390 *
391 * @param other
392 * the path string to resolve against this path
393 *
394 * @return the resulting path
395 *
396 * @throws InvalidPathException
397 * if the path string cannot be converted to a Path.
398 *
399 * @see FileSystem#getPath
400 */
401 default Path resolve(String other) {
402 return resolve(getFileSystem().getPath(other));
403 }
404
405 /**
406 * Resolves the given path against this path's {@link #getParent parent}
407 * path. This is useful where a file name needs to be <i>replaced</i> with
408 * another file name. For example, suppose that the name separator is
409 * "{@code /}" and a path represents "{@code dir1/dir2/foo}", then invoking
410 * this method with the {@code Path} "{@code bar}" will result in the {@code
411 * Path} "{@code dir1/dir2/bar}". If this path does not have a parent path,
412 * or {@code other} is {@link #isAbsolute() absolute}, then this method
413 * returns {@code other}. If {@code other} is an empty path then this method
414 * returns this path's parent, or where this path doesn't have a parent, the
415 * empty path.
416 *
417 * @implSpec
418 * The default implementation is equivalent for this path to:
419 * <pre>{@code
420 * (getParent() == null) ? other : getParent().resolve(other);
421 * }</pre>
422 * unless {@code other == null}, in which case a
423 * {@code NullPointerException} is thrown.
424 *
425 * @param other
426 * the path to resolve against this path's parent
427 *
428 * @return the resulting path
429 *
430 * @see #resolve(Path)
431 */
432 default Path resolveSibling(Path other) {
433 if (other == null)
434 throw new NullPointerException();
435 Path parent = getParent();
436 return (parent == null) ? other : parent.resolve(other);
437 }
438
439 /**
440 * Converts a given path string to a {@code Path} and resolves it against
441 * this path's {@link #getParent parent} path in exactly the manner
442 * specified by the {@link #resolveSibling(Path) resolveSibling} method.
443 *
444 * @implSpec
445 * The default implementation is equivalent for this path to:
446 * <pre>{@code
447 * resolveSibling(getFileSystem().getPath(other));
448 * }</pre>
449 *
450 * @param other
451 * the path string to resolve against this path's parent
452 *
453 * @return the resulting path
454 *
455 * @throws InvalidPathException
456 * if the path string cannot be converted to a Path.
457 *
458 * @see FileSystem#getPath
459 */
460 default Path resolveSibling(String other) {
461 return resolveSibling(getFileSystem().getPath(other));
462 }
463
464 /**
465 * Constructs a relative path between this path and a given path.
466 *
467 * <p> Relativization is the inverse of {@link #resolve(Path) resolution}.
468 * This method attempts to construct a {@link #isAbsolute relative} path
469 * that when {@link #resolve(Path) resolved} against this path, yields a
470 * path that locates the same file as the given path. For example, on UNIX,
471 * if this path is {@code "/a/b"} and the given path is {@code "/a/b/c/d"}
472 * then the resulting relative path would be {@code "c/d"}. Where this
473 * path and the given path do not have a {@link #getRoot root} component,
474 * then a relative path can be constructed. A relative path cannot be
475 * constructed if only one of the paths have a root component. Where both
476 * paths have a root component then it is implementation dependent if a
477 * relative path can be constructed. If this path and the given path are
478 * {@link #equals equal} then an <i>empty path</i> is returned.
479 *
480 * <p> For any two {@link #normalize normalized} paths <i>p</i> and
481 * <i>q</i>, where <i>q</i> does not have a root component,
482 * <blockquote>
483 * <i>p</i><tt>.relativize(</tt><i>p</i><tt>.resolve(</tt><i>q</i><tt>)).equals(</tt><i>q</i><tt>)</tt>
484 * </blockquote>
485 *
486 * <p> When symbolic links are supported, then whether the resulting path,
487 * when resolved against this path, yields a path that can be used to locate
488 * the {@link Files#isSameFile same} file as {@code other} is implementation
489 * dependent. For example, if this path is {@code "/a/b"} and the given
490 * path is {@code "/a/x"} then the resulting relative path may be {@code
491 * "../x"}. If {@code "b"} is a symbolic link then is implementation
492 * dependent if {@code "a/b/../x"} would locate the same file as {@code "/a/x"}.
493 *
494 * @param other
495 * the path to relativize against this path
496 *
497 * @return the resulting relative path, or an empty path if both paths are
498 * equal
499 *
500 * @throws IllegalArgumentException
501 * if {@code other} is not a {@code Path} that can be relativized
502 * against this path
503 */
504 Path relativize(Path other);
505
506 /**
507 * Returns a URI to represent this path.
508 *
509 * <p> This method constructs an absolute {@link URI} with a {@link
510 * URI#getScheme() scheme} equal to the URI scheme that identifies the
511 * provider. The exact form of the scheme specific part is highly provider
512 * dependent.
513 *
514 * <p> In the case of the default provider, the URI is hierarchical with
515 * a {@link URI#getPath() path} component that is absolute. The query and
516 * fragment components are undefined. Whether the authority component is
517 * defined or not is implementation dependent. There is no guarantee that
518 * the {@code URI} may be used to construct a {@link java.io.File java.io.File}.
519 * In particular, if this path represents a Universal Naming Convention (UNC)
520 * path, then the UNC server name may be encoded in the authority component
521 * of the resulting URI. In the case of the default provider, and the file
522 * exists, and it can be determined that the file is a directory, then the
523 * resulting {@code URI} will end with a slash.
524 *
525 * <p> The default provider provides a similar <em>round-trip</em> guarantee
526 * to the {@link java.io.File} class. For a given {@code Path} <i>p</i> it
527 * is guaranteed that
528 * <blockquote><tt>
529 * {@link Paths#get(URI) Paths.get}(</tt><i>p</i><tt>.toUri()).equals(</tt><i>p</i>
530 * <tt>.{@link #toAbsolutePath() toAbsolutePath}())</tt>
531 * </blockquote>
532 * so long as the original {@code Path}, the {@code URI}, and the new {@code
533 * Path} are all created in (possibly different invocations of) the same
534 * Java virtual machine. Whether other providers make any guarantees is
535 * provider specific and therefore unspecified.
536 *
537 * <p> When a file system is constructed to access the contents of a file
538 * as a file system then it is highly implementation specific if the returned
539 * URI represents the given path in the file system or it represents a
540 * <em>compound</em> URI that encodes the URI of the enclosing file system.
541 * A format for compound URIs is not defined in this release; such a scheme
542 * may be added in a future release.
543 *
544 * @return the URI representing this path
545 *
546 * @throws java.io.IOError
547 * if an I/O error occurs obtaining the absolute path, or where a
548 * file system is constructed to access the contents of a file as
549 * a file system, and the URI of the enclosing file system cannot be
550 * obtained
551 *
552 * @throws SecurityException
553 * In the case of the default provider, and a security manager
554 * is installed, the {@link #toAbsolutePath toAbsolutePath} method
555 * throws a security exception.
556 */
557 URI toUri();
558
559 /**
560 * Returns a {@code Path} object representing the absolute path of this
561 * path.
562 *
563 * <p> If this path is already {@link Path#isAbsolute absolute} then this
564 * method simply returns this path. Otherwise, this method resolves the path
565 * in an implementation dependent manner, typically by resolving the path
566 * against a file system default directory. Depending on the implementation,
567 * this method may throw an I/O error if the file system is not accessible.
568 *
569 * @return a {@code Path} object representing the absolute path
570 *
571 * @throws java.io.IOError
572 * if an I/O error occurs
573 * @throws SecurityException
574 * In the case of the default provider, a security manager
575 * is installed, and this path is not absolute, then the security
576 * manager's {@link SecurityManager#checkPropertyAccess(String)
577 * checkPropertyAccess} method is invoked to check access to the
578 * system property {@code user.dir}
579 */
580 Path toAbsolutePath();
581
582 /**
583 * Returns the <em>real</em> path of an existing file.
584 *
585 * <p> The precise definition of this method is implementation dependent but
586 * in general it derives from this path, an {@link #isAbsolute absolute}
587 * path that locates the {@link Files#isSameFile same} file as this path, but
588 * with name elements that represent the actual name of the directories
589 * and the file. For example, where filename comparisons on a file system
590 * are case insensitive then the name elements represent the names in their
591 * actual case. Additionally, the resulting path has redundant name
592 * elements removed.
593 *
594 * <p> If this path is relative then its absolute path is first obtained,
595 * as if by invoking the {@link #toAbsolutePath toAbsolutePath} method.
596 *
597 * <p> The {@code options} array may be used to indicate how symbolic links
598 * are handled. By default, symbolic links are resolved to their final
599 * target. If the option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is
600 * present then this method does not resolve symbolic links.
601 *
602 * Some implementations allow special names such as "{@code ..}" to refer to
603 * the parent directory. When deriving the <em>real path</em>, and a
604 * "{@code ..}" (or equivalent) is preceded by a non-"{@code ..}" name then
605 * an implementation will typically cause both names to be removed. When
606 * not resolving symbolic links and the preceding name is a symbolic link
607 * then the names are only removed if it guaranteed that the resulting path
608 * will locate the same file as this path.
609 *
610 * @param options
611 * options indicating how symbolic links are handled
612 *
613 * @return an absolute path represent the <em>real</em> path of the file
614 * located by this object
615 *
616 * @throws IOException
617 * if the file does not exist or an I/O error occurs
618 * @throws SecurityException
619 * In the case of the default provider, and a security manager
620 * is installed, its {@link SecurityManager#checkRead(String) checkRead}
621 * method is invoked to check read access to the file, and where
622 * this path is not absolute, its {@link SecurityManager#checkPropertyAccess(String)
623 * checkPropertyAccess} method is invoked to check access to the
624 * system property {@code user.dir}
625 */
626 Path toRealPath(LinkOption... options) throws IOException;
627
628 /**
629 * Returns a {@link File} object representing this path. Where this {@code
630 * Path} is associated with the default provider, then this method is
631 * equivalent to returning a {@code File} object constructed with the
632 * {@code String} representation of this path.
633 *
634 * <p> If this path was created by invoking the {@code File} {@link
635 * File#toPath toPath} method then there is no guarantee that the {@code
636 * File} object returned by this method is {@link #equals equal} to the
637 * original {@code File}.
638 *
639 * @implSpec
640 * The default implementation is equivalent for this path to:
641 * <pre>{@code
642 * new File(toString());
643 * }</pre>
644 * if the {@code FileSystem} which created this {@code Path} is the default
645 * file system; otherwise an {@code UnsupportedOperationException} is
646 * thrown.
647 *
648 * @return a {@code File} object representing this path
649 *
650 * @throws UnsupportedOperationException
651 * if this {@code Path} is not associated with the default provider
652 */
653 default File toFile() {
654 if (getFileSystem() == FileSystems.getDefault()) {
655 return new File(toString());
656 } else {
657 throw new UnsupportedOperationException("Path not associated with "
658 + "default file system.");
659 }
660 }
661
662 // -- watchable --
663
664 /**
665 * Registers the file located by this path with a watch service.
666 *
667 * <p> In this release, this path locates a directory that exists. The
668 * directory is registered with the watch service so that entries in the
669 * directory can be watched. The {@code events} parameter is the events to
670 * register and may contain the following events:
671 * <ul>
672 * <li>{@link StandardWatchEventKinds#ENTRY_CREATE ENTRY_CREATE} -
673 * entry created or moved into the directory</li>
674 * <li>{@link StandardWatchEventKinds#ENTRY_DELETE ENTRY_DELETE} -
675 * entry deleted or moved out of the directory</li>
676 * <li>{@link StandardWatchEventKinds#ENTRY_MODIFY ENTRY_MODIFY} -
677 * entry in directory was modified</li>
678 * </ul>
679 *
680 * <p> The {@link WatchEvent#context context} for these events is the
681 * relative path between the directory located by this path, and the path
682 * that locates the directory entry that is created, deleted, or modified.
683 *
684 * <p> The set of events may include additional implementation specific
685 * event that are not defined by the enum {@link StandardWatchEventKinds}
686 *
687 * <p> The {@code modifiers} parameter specifies <em>modifiers</em> that
688 * qualify how the directory is registered. This release does not define any
689 * <em>standard</em> modifiers. It may contain implementation specific
690 * modifiers.
691 *
692 * <p> Where a file is registered with a watch service by means of a symbolic
693 * link then it is implementation specific if the watch continues to depend
694 * on the existence of the symbolic link after it is registered.
695 *
696 * @param watcher
697 * the watch service to which this object is to be registered
698 * @param events
699 * the events for which this object should be registered
700 * @param modifiers
701 * the modifiers, if any, that modify how the object is registered
702 *
703 * @return a key representing the registration of this object with the
704 * given watch service
705 *
706 * @throws UnsupportedOperationException
707 * if unsupported events or modifiers are specified
708 * @throws IllegalArgumentException
709 * if an invalid combination of events or modifiers is specified
710 * @throws ClosedWatchServiceException
711 * if the watch service is closed
712 * @throws NotDirectoryException
713 * if the file is registered to watch the entries in a directory
714 * and the file is not a directory <i>(optional specific exception)</i>
715 * @throws IOException
716 * if an I/O error occurs
717 * @throws SecurityException
718 * In the case of the default provider, and a security manager is
719 * installed, the {@link SecurityManager#checkRead(String) checkRead}
720 * method is invoked to check read access to the file.
721 */
722 @Override
723 WatchKey register(WatchService watcher,
724 WatchEvent.Kind<?>[] events,
725 WatchEvent.Modifier... modifiers)
726 throws IOException;
727
728 /**
729 * Registers the file located by this path with a watch service.
730 *
731 * <p> An invocation of this method behaves in exactly the same way as the
732 * invocation
733 * <pre>
734 * watchable.{@link #register(WatchService,WatchEvent.Kind[],WatchEvent.Modifier[]) register}(watcher, events, new WatchEvent.Modifier[0]);
735 * </pre>
736 *
737 * <p> <b>Usage Example:</b>
738 * Suppose we wish to register a directory for entry create, delete, and modify
739 * events:
740 * <pre>
741 * Path dir = ...
742 * WatchService watcher = ...
743 *
744 * WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
745 * </pre>
746 *
747 * @implSpec
748 * The default implementation is equivalent for this path to:
749 * <pre>{@code
750 * register(watcher, events, new WatchEvent.Modifier[0]);
751 * }</pre>
752 *
753 * @param watcher
754 * The watch service to which this object is to be registered
755 * @param events
756 * The events for which this object should be registered
757 *
758 * @return A key representing the registration of this object with the
759 * given watch service
760 *
761 * @throws UnsupportedOperationException
762 * If unsupported events are specified
763 * @throws IllegalArgumentException
764 * If an invalid combination of events is specified
765 * @throws ClosedWatchServiceException
766 * If the watch service is closed
767 * @throws NotDirectoryException
768 * If the file is registered to watch the entries in a directory
769 * and the file is not a directory <i>(optional specific exception)</i>
770 * @throws IOException
771 * If an I/O error occurs
772 * @throws SecurityException
773 * In the case of the default provider, and a security manager is
774 * installed, the {@link SecurityManager#checkRead(String) checkRead}
775 * method is invoked to check read access to the file.
776 */
777 @Override
778 default WatchKey register(WatchService watcher,
779 WatchEvent.Kind<?>... events) throws IOException {
780 return register(watcher, events, new WatchEvent.Modifier[0]);
781 }
782
783 // -- Iterable --
784
785 /**
786 * Returns an iterator over the name elements of this path.
787 *
788 * <p> The first element returned by the iterator represents the name
789 * element that is closest to the root in the directory hierarchy, the
790 * second element is the next closest, and so on. The last element returned
791 * is the name of the file or directory denoted by this path. The {@link
792 * #getRoot root} component, if present, is not returned by the iterator.
793 *
794 * @implSpec
795 * The default implementation returns an {@code Iterator<Path>} which, for
796 * this path, traverses the {@code Path}s returned by
797 * {@code getName(index)}, where {@code index} ranges from zero to
798 * {@code getNameCount() - 1}, inclusive.
799 *
800 * @return an iterator over the name elements of this path.
801 */
802 @Override
803 default Iterator<Path> iterator() {
804 return new Iterator<>() {
805 private int i = 0;
806
807 @Override
808 public boolean hasNext() {
809 return (i < getNameCount());
810 }
811
812 @Override
813 public Path next() {
814 if (i < getNameCount()) {
815 Path result = getName(i);
816 i++;
817 return result;
818 } else {
819 throw new NoSuchElementException();
820 }
821 }
822 };
823 }
824
825 // -- compareTo/equals/hashCode --
826
827 /**
828 * Compares two abstract paths lexicographically. The ordering defined by
829 * this method is provider specific, and in the case of the default
830 * provider, platform specific. This method does not access the file system
831 * and neither file is required to exist.
832 *
833 * <p> This method may not be used to compare paths that are associated
834 * with different file system providers.
835 *
836 * @param other the path compared to this path.
837 *
838 * @return zero if the argument is {@link #equals equal} to this path, a
839 * value less than zero if this path is lexicographically less than
840 * the argument, or a value greater than zero if this path is
841 * lexicographically greater than the argument
842 *
843 * @throws ClassCastException
844 * if the paths are associated with different providers
845 */
846 @Override
847 int compareTo(Path other);
848
849 /**
850 * Tests this path for equality with the given object.
851 *
852 * <p> If the given object is not a Path, or is a Path associated with a
853 * different {@code FileSystem}, then this method returns {@code false}.
854 *
855 * <p> Whether or not two path are equal depends on the file system
856 * implementation. In some cases the paths are compared without regard
857 * to case, and others are case sensitive. This method does not access the
858 * file system and the file is not required to exist. Where required, the
859 * {@link Files#isSameFile isSameFile} method may be used to check if two
860 * paths locate the same file.
861 *
862 * <p> This method satisfies the general contract of the {@link
863 * java.lang.Object#equals(Object) Object.equals} method. </p>
864 *
865 * @param other
866 * the object to which this object is to be compared
867 *
868 * @return {@code true} if, and only if, the given object is a {@code Path}
869 * that is identical to this {@code Path}
870 */
871 boolean equals(Object other);
872
873 /**
874 * Computes a hash code for this path.
875 *
876 * <p> The hash code is based upon the components of the path, and
877 * satisfies the general contract of the {@link Object#hashCode
878 * Object.hashCode} method.
879 *
880 * @return the hash-code value for this path
881 */
882 int hashCode();
883
884 /**
885 * Returns the string representation of this path.
886 *
887 * <p> If this path was created by converting a path string using the
888 * {@link FileSystem#getPath getPath} method then the path string returned
889 * by this method may differ from the original String used to create the path.
890 *
891 * <p> The returned path string uses the default name {@link
892 * FileSystem#getSeparator separator} to separate names in the path.
893 *
894 * @return the string representation of this path
895 */
896 String toString();
897 }