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).
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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 import java.util.Objects;
34 import java.util.stream.Stream;
35
36 /**
37 * An object that may be used to locate a file in a file system. It will
38 * typically represent a system dependent file path.
39 *
40 * <p> A {@code Path} represents a path that is hierarchical and composed of a
41 * sequence of directory and file name elements separated by a special separator
42 * or delimiter. A <em>root component</em>, that identifies a file system
43 * hierarchy, may also be present. The name element that is <em>farthest</em>
44 * from the root of the directory hierarchy is the name of a file or directory.
45 * The other name elements are directory names. A {@code Path} can represent a
46 * root, a root and a sequence of names, or simply one or more name elements.
47 * A {@code Path} is considered to be an <i>empty path</i> if it consists
48 * solely of one name element that is empty. Accessing a file using an
49 * <i>empty path</i> is equivalent to accessing the default directory of the
50 * file system. {@code Path} defines the {@link #getFileName() getFileName},
51 * {@link #getParent getParent}, {@link #getRoot getRoot}, and {@link #subpath
52 * subpath} methods to access the path components or a subsequence of its name
53 * elements.
54 *
55 * <p> In addition to accessing the components of a path, a {@code Path} also
56 * defines the {@link #resolve(Path) resolve} and {@link #resolveSibling(Path)
57 * resolveSibling} methods to combine paths. The {@link #relativize relativize}
58 * method that can be used to construct a relative path between two paths.
59 * Paths can be {@link #compareTo compared}, and tested against each other using
60 * the {@link #startsWith startsWith} and {@link #endsWith endsWith} methods.
61 *
62 * <p> This interface extends {@link Watchable} interface so that a directory
63 * located by a path can be {@link #register registered} with a {@link
64 * WatchService} and entries in the directory watched. </p>
65 *
66 * <p> <b>WARNING:</b> This interface is only intended to be implemented by
67 * those developing custom file system implementations. Methods may be added to
68 * this interface in future releases. </p>
69 *
70 * <h2>Accessing Files</h2>
71 * <p> Paths may be used with the {@link Files} class to operate on files,
72 * directories, and other types of files. For example, suppose we want a {@link
73 * java.io.BufferedReader} to read text from a file "{@code access.log}". The
74 * file is located in a directory "{@code logs}" relative to the current working
75 * directory and is UTF-8 encoded.
76 * <pre>
77 * Path path = FileSystems.getDefault().getPath("logs", "access.log");
78 * BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8);
79 * </pre>
80 *
81 * <a id="interop"></a><h2>Interoperability</h2>
82 * <p> Paths associated with the default {@link
83 * java.nio.file.spi.FileSystemProvider provider} are generally interoperable
84 * with the {@link java.io.File java.io.File} class. Paths created by other
85 * providers are unlikely to be interoperable with the abstract path names
86 * represented by {@code java.io.File}. The {@link java.io.File#toPath toPath}
87 * method may be used to obtain a {@code Path} from the abstract path name
88 * represented by a {@code java.io.File} object. The resulting {@code Path} can
89 * be used to operate on the same file as the {@code java.io.File} object. In
90 * addition, the {@link #toFile toFile} method is useful to construct a {@code
91 * File} from the {@code String} representation of a {@code Path}.
92 *
93 * <h2>Concurrency</h2>
94 * <p> Implementations of this interface are immutable and safe for use by
95 * multiple concurrent threads.
96 *
97 * @since 1.7
98 * @see Paths
99 */
100
101 public interface Path
102 extends Comparable<Path>, Iterable<Path>, Watchable
103 {
104 /**
105 * Returns the file system that created this object.
106 *
107 * @return the file system that created this object
108 */
109 FileSystem getFileSystem();
110
111 /**
112 * Tells whether or not this path is absolute.
113 *
114 * <p> An absolute path is complete in that it doesn't need to be combined
115 * with other path information in order to locate a file.
116 *
117 * @return {@code true} if, and only if, this path is absolute
118 */
119 boolean isAbsolute();
120
121 /**
122 * Returns the root component of this path as a {@code Path} object,
123 * or {@code null} if this path does not have a root component.
124 *
125 * @return a path representing the root component of this path,
126 * or {@code null}
127 */
128 Path getRoot();
129
130 /**
131 * Returns the name of the file or directory denoted by this path as a
132 * {@code Path} object. The file name is the <em>farthest</em> element from
133 * the root in the directory hierarchy.
134 *
135 * @return a path representing the name of the file or directory, or
136 * {@code null} if this path has zero elements
137 */
138 Path getFileName();
139
140 /**
141 * Returns the <em>parent path</em>, or {@code null} if this path does not
142 * have a parent.
143 *
144 * <p> The parent of this path object consists of this path's root
145 * component, if any, and each element in the path except for the
146 * <em>farthest</em> from the root in the directory hierarchy. This method
147 * does not access the file system; the path or its parent may not exist.
148 * Furthermore, this method does not eliminate special names such as "."
149 * and ".." that may be used in some implementations. On UNIX for example,
150 * the parent of "{@code /a/b/c}" is "{@code /a/b}", and the parent of
151 * {@code "x/y/.}" is "{@code x/y}". This method may be used with the {@link
152 * #normalize normalize} method, to eliminate redundant names, for cases where
153 * <em>shell-like</em> navigation is required.
154 *
155 * <p> If this path has more than one element, and no root component, then
156 * this method is equivalent to evaluating the expression:
157 * <blockquote><pre>
158 * subpath(0, getNameCount()-1);
159 * </pre></blockquote>
160 *
161 * @return a path representing the path's parent
162 */
163 Path getParent();
164
165 /**
166 * Returns the number of name elements in the path.
167 *
168 * @return the number of elements in the path, or {@code 0} if this path
169 * only represents a root component
170 */
171 int getNameCount();
172
173 /**
174 * Returns a name element of this path as a {@code Path} object.
175 *
176 * <p> The {@code index} parameter is the index of the name element to return.
177 * The element that is <em>closest</em> to the root in the directory hierarchy
178 * has index {@code 0}. The element that is <em>farthest</em> from the root
179 * has index {@link #getNameCount count}{@code -1}.
180 *
181 * @param index
182 * the index of the element
183 *
184 * @return the name element
185 *
186 * @throws IllegalArgumentException
187 * if {@code index} is negative, {@code index} is greater than or
188 * equal to the number of elements, or this path has zero name
189 * elements
190 */
191 Path getName(int index);
192
193 /**
194 * Returns a relative {@code Path} that is a subsequence of the name
195 * elements of this path.
196 *
197 * <p> The {@code beginIndex} and {@code endIndex} parameters specify the
198 * subsequence of name elements. The name that is <em>closest</em> to the root
199 * in the directory hierarchy has index {@code 0}. The name that is
200 * <em>farthest</em> from the root has index {@link #getNameCount
201 * count}{@code -1}. The returned {@code Path} object has the name elements
202 * that begin at {@code beginIndex} and extend to the element at index {@code
203 * endIndex-1}.
204 *
205 * @param beginIndex
206 * the index of the first element, inclusive
207 * @param endIndex
208 * the index of the last element, exclusive
209 *
210 * @return a new {@code Path} object that is a subsequence of the name
211 * elements in this {@code Path}
212 *
213 * @throws IllegalArgumentException
214 * if {@code beginIndex} is negative, or greater than or equal to
215 * the number of elements. If {@code endIndex} is less than or
216 * equal to {@code beginIndex}, or larger than the number of elements.
217 */
218 Path subpath(int beginIndex, int endIndex);
219
220 /**
221 * Tests if this path starts with the given path.
222 *
223 * <p> This path <em>starts</em> with the given path if this path's root
224 * component <em>starts</em> with the root component of the given path,
225 * and this path starts with the same name elements as the given path.
226 * If the given path has more name elements than this path then {@code false}
227 * is returned.
228 *
229 * <p> Whether or not the root component of this path starts with the root
230 * component of the given path is file system specific. If this path does
231 * not have a root component and the given path has a root component then
232 * this path does not start with the given path.
233 *
234 * <p> If the given path is associated with a different {@code FileSystem}
235 * to this path then {@code false} is returned.
236 *
237 * @param other
238 * the given path
239 *
240 * @return {@code true} if this path starts with the given path; otherwise
241 * {@code false}
242 */
243 boolean startsWith(Path other);
244
245 /**
246 * Tests if this path starts with a {@code Path}, constructed by converting
247 * the given path string, in exactly the manner specified by the {@link
248 * #startsWith(Path) startsWith(Path)} method. On UNIX for example, the path
249 * "{@code foo/bar}" starts with "{@code foo}" and "{@code foo/bar}". It
250 * does not start with "{@code f}" or "{@code fo}".
251 *
252 * @implSpec
253 * The default implementation is equivalent for this path to:
254 * <pre>{@code
255 * startsWith(getFileSystem().getPath(other));
256 * }</pre>
257 *
258 * @param other
259 * the given path string
260 *
261 * @return {@code true} if this path starts with the given path; otherwise
262 * {@code false}
263 *
264 * @throws InvalidPathException
265 * If the path string cannot be converted to a Path.
266 */
267 default boolean startsWith(String other) {
268 return startsWith(getFileSystem().getPath(other));
269 }
270
271 /**
272 * Tests if this path ends with the given path.
273 *
274 * <p> If the given path has <em>N</em> elements, and no root component,
275 * and this path has <em>N</em> or more elements, then this path ends with
276 * the given path if the last <em>N</em> elements of each path, starting at
277 * the element farthest from the root, are equal.
278 *
279 * <p> If the given path has a root component then this path ends with the
280 * given path if the root component of this path <em>ends with</em> the root
281 * component of the given path, and the corresponding elements of both paths
282 * are equal. Whether or not the root component of this path ends with the
283 * root component of the given path is file system specific. If this path
284 * does not have a root component and the given path has a root component
285 * then this path does not end with the given path.
286 *
287 * <p> If the given path is associated with a different {@code FileSystem}
288 * to this path then {@code false} is returned.
289 *
290 * @param other
291 * the given path
292 *
293 * @return {@code true} if this path ends with the given path; otherwise
294 * {@code false}
295 */
296 boolean endsWith(Path other);
297
298 /**
299 * Tests if this path ends with a {@code Path}, constructed by converting
300 * the given path string, in exactly the manner specified by the {@link
301 * #endsWith(Path) endsWith(Path)} method. On UNIX for example, the path
302 * "{@code foo/bar}" ends with "{@code foo/bar}" and "{@code bar}". It does
303 * not end with "{@code r}" or "{@code /bar}". Note that trailing separators
304 * are not taken into account, and so invoking this method on the {@code
305 * Path}"{@code foo/bar}" with the {@code String} "{@code bar/}" returns
306 * {@code true}.
307 *
308 * @implSpec
309 * The default implementation is equivalent for this path to:
310 * <pre>{@code
311 * endsWith(getFileSystem().getPath(other));
312 * }</pre>
313 *
314 * @param other
315 * the given path string
316 *
317 * @return {@code true} if this path ends with the given path; otherwise
318 * {@code false}
319 *
320 * @throws InvalidPathException
321 * If the path string cannot be converted to a Path.
322 */
323 default boolean endsWith(String other) {
324 return endsWith(getFileSystem().getPath(other));
325 }
326
327 /**
328 * Returns whether the extension of this path is in a specified list.
329 * The extension is that portion of the path after the last dot
330 * ({@code '.'}). If this path is empty, ends with a dot, or has a
331 * {@link FileSystem#getSeparator() name-separator} after the last dot,
332 * or the parameter is empty, then this method returns {@code false}.
333 * Any arguments in the parameter which are either empty or contain a
334 * dot are ignored.
335 *
336 * @param extensions
337 * the extensions to be checked
338 *
339 * @return whether this path has one of the specified extensions
340 */
341 default boolean hasExtension(String... extensions) {
342 Objects.requireNonNull(extensions);
343
344 String path = toString();
345 if (path.isEmpty()) {
346 return false;
347 }
348
349 int lastDot = path.lastIndexOf(".");
350 if (lastDot == path.length() - 1) {
351 return false;
352 }
353
354 String separator = getFileSystem().getSeparator();
355 if (path.indexOf(separator, lastDot) != -1) {
356 return false;
357 }
358
359 return Stream.of(extensions)
360 .filter(e -> !e.isEmpty() && !e.contains("."))
361 .anyMatch(path::endsWith);
362 }
363
364 /**
365 * Returns a path that is this path with redundant name elements eliminated.
366 *
367 * <p> The precise definition of this method is implementation dependent but
368 * in general it derives from this path, a path that does not contain
369 * <em>redundant</em> name elements. In many file systems, the "{@code .}"
370 * and "{@code ..}" are special names used to indicate the current directory
371 * and parent directory. In such file systems all occurrences of "{@code .}"
372 * are considered redundant. If a "{@code ..}" is preceded by a
373 * non-"{@code ..}" name then both names are considered redundant (the
374 * process to identify such names is repeated until it is no longer
375 * applicable).
376 *
377 * <p> This method does not access the file system; the path may not locate
378 * a file that exists. Eliminating "{@code ..}" and a preceding name from a
379 * path may result in the path that locates a different file than the original
380 * path. This can arise when the preceding name is a symbolic link.
381 *
382 * @return the resulting path or this path if it does not contain
383 * redundant name elements; an empty path is returned if this path
384 * does not have a root component and all name elements are redundant
385 *
386 * @see #getParent
387 * @see #toRealPath
388 */
389 Path normalize();
390
391 // -- resolution and relativization --
392
393 /**
394 * Resolve the given path against this path.
395 *
396 * <p> If the {@code other} parameter is an {@link #isAbsolute() absolute}
397 * path then this method trivially returns {@code other}. If {@code other}
398 * is an <i>empty path</i> then this method trivially returns this path.
399 * Otherwise this method considers this path to be a directory and resolves
400 * the given path against this path. In the simplest case, the given path
401 * does not have a {@link #getRoot root} component, in which case this method
402 * <em>joins</em> the given path to this path and returns a resulting path
403 * that {@link #endsWith ends} with the given path. Where the given path has
404 * a root component then resolution is highly implementation dependent and
405 * therefore unspecified.
406 *
407 * @param other
408 * the path to resolve against this path
409 *
410 * @return the resulting path
411 *
412 * @see #relativize
413 */
414 Path resolve(Path other);
415
416 /**
417 * Converts a given path string to a {@code Path} and resolves it against
418 * this {@code Path} in exactly the manner specified by the {@link
419 * #resolve(Path) resolve} method. For example, suppose that the name
420 * separator is "{@code /}" and a path represents "{@code foo/bar}", then
421 * invoking this method with the path string "{@code gus}" will result in
422 * the {@code Path} "{@code foo/bar/gus}".
423 *
424 * @implSpec
425 * The default implementation is equivalent for this path to:
426 * <pre>{@code
427 * resolve(getFileSystem().getPath(other));
428 * }</pre>
429 *
430 * @param other
431 * the path string to resolve against this path
432 *
433 * @return the resulting path
434 *
435 * @throws InvalidPathException
436 * if the path string cannot be converted to a Path.
437 *
438 * @see FileSystem#getPath
439 */
440 default Path resolve(String other) {
441 return resolve(getFileSystem().getPath(other));
442 }
443
444 /**
445 * Resolves the given path against this path's {@link #getParent parent}
446 * path. This is useful where a file name needs to be <i>replaced</i> with
447 * another file name. For example, suppose that the name separator is
448 * "{@code /}" and a path represents "{@code dir1/dir2/foo}", then invoking
449 * this method with the {@code Path} "{@code bar}" will result in the {@code
450 * Path} "{@code dir1/dir2/bar}". If this path does not have a parent path,
451 * or {@code other} is {@link #isAbsolute() absolute}, then this method
452 * returns {@code other}. If {@code other} is an empty path then this method
453 * returns this path's parent, or where this path doesn't have a parent, the
454 * empty path.
455 *
456 * @implSpec
457 * The default implementation is equivalent for this path to:
458 * <pre>{@code
459 * (getParent() == null) ? other : getParent().resolve(other);
460 * }</pre>
461 * unless {@code other == null}, in which case a
462 * {@code NullPointerException} is thrown.
463 *
464 * @param other
465 * the path to resolve against this path's parent
466 *
467 * @return the resulting path
468 *
469 * @see #resolve(Path)
470 */
471 default Path resolveSibling(Path other) {
472 if (other == null)
473 throw new NullPointerException();
474 Path parent = getParent();
475 return (parent == null) ? other : parent.resolve(other);
476 }
477
478 /**
479 * Converts a given path string to a {@code Path} and resolves it against
480 * this path's {@link #getParent parent} path in exactly the manner
481 * specified by the {@link #resolveSibling(Path) resolveSibling} method.
482 *
483 * @implSpec
484 * The default implementation is equivalent for this path to:
485 * <pre>{@code
486 * resolveSibling(getFileSystem().getPath(other));
487 * }</pre>
488 *
489 * @param other
490 * the path string to resolve against this path's parent
491 *
492 * @return the resulting path
493 *
494 * @throws InvalidPathException
495 * if the path string cannot be converted to a Path.
496 *
497 * @see FileSystem#getPath
498 */
499 default Path resolveSibling(String other) {
500 return resolveSibling(getFileSystem().getPath(other));
501 }
502
503 /**
504 * Constructs a relative path between this path and a given path.
505 *
506 * <p> Relativization is the inverse of {@link #resolve(Path) resolution}.
507 * This method attempts to construct a {@link #isAbsolute relative} path
508 * that when {@link #resolve(Path) resolved} against this path, yields a
509 * path that locates the same file as the given path. For example, on UNIX,
510 * if this path is {@code "/a/b"} and the given path is {@code "/a/b/c/d"}
511 * then the resulting relative path would be {@code "c/d"}. Where this
512 * path and the given path do not have a {@link #getRoot root} component,
513 * then a relative path can be constructed. A relative path cannot be
514 * constructed if only one of the paths have a root component. Where both
515 * paths have a root component then it is implementation dependent if a
516 * relative path can be constructed. If this path and the given path are
517 * {@link #equals equal} then an <i>empty path</i> is returned.
518 *
519 * <p> For any two {@link #normalize normalized} paths <i>p</i> and
520 * <i>q</i>, where <i>q</i> does not have a root component,
521 * <blockquote>
522 * <i>p</i>{@code .relativize(}<i>p</i>
523 * {@code .resolve(}<i>q</i>{@code )).equals(}<i>q</i>{@code )}
524 * </blockquote>
525 *
526 * <p> When symbolic links are supported, then whether the resulting path,
527 * when resolved against this path, yields a path that can be used to locate
528 * the {@link Files#isSameFile same} file as {@code other} is implementation
529 * dependent. For example, if this path is {@code "/a/b"} and the given
530 * path is {@code "/a/x"} then the resulting relative path may be {@code
531 * "../x"}. If {@code "b"} is a symbolic link then is implementation
532 * dependent if {@code "a/b/../x"} would locate the same file as {@code "/a/x"}.
533 *
534 * @param other
535 * the path to relativize against this path
536 *
537 * @return the resulting relative path, or an empty path if both paths are
538 * equal
539 *
540 * @throws IllegalArgumentException
541 * if {@code other} is not a {@code Path} that can be relativized
542 * against this path
543 */
544 Path relativize(Path other);
545
546 /**
547 * Returns a URI to represent this path.
548 *
549 * <p> This method constructs an absolute {@link URI} with a {@link
550 * URI#getScheme() scheme} equal to the URI scheme that identifies the
551 * provider. The exact form of the scheme specific part is highly provider
552 * dependent.
553 *
554 * <p> In the case of the default provider, the URI is hierarchical with
555 * a {@link URI#getPath() path} component that is absolute. The query and
556 * fragment components are undefined. Whether the authority component is
557 * defined or not is implementation dependent. There is no guarantee that
558 * the {@code URI} may be used to construct a {@link java.io.File java.io.File}.
559 * In particular, if this path represents a Universal Naming Convention (UNC)
560 * path, then the UNC server name may be encoded in the authority component
561 * of the resulting URI. In the case of the default provider, and the file
562 * exists, and it can be determined that the file is a directory, then the
563 * resulting {@code URI} will end with a slash.
564 *
565 * <p> The default provider provides a similar <em>round-trip</em> guarantee
566 * to the {@link java.io.File} class. For a given {@code Path} <i>p</i> it
567 * is guaranteed that
568 * <blockquote>
569 * {@link Paths#get(URI) Paths.get}{@code (}<i>p</i>{@code .toUri()).equals(}<i>p</i>
570 * {@code .}{@link #toAbsolutePath() toAbsolutePath}{@code ())}
571 * </blockquote>
572 * so long as the original {@code Path}, the {@code URI}, and the new {@code
573 * Path} are all created in (possibly different invocations of) the same
574 * Java virtual machine. Whether other providers make any guarantees is
575 * provider specific and therefore unspecified.
576 *
577 * <p> When a file system is constructed to access the contents of a file
578 * as a file system then it is highly implementation specific if the returned
579 * URI represents the given path in the file system or it represents a
580 * <em>compound</em> URI that encodes the URI of the enclosing file system.
581 * A format for compound URIs is not defined in this release; such a scheme
582 * may be added in a future release.
583 *
584 * @return the URI representing this path
585 *
586 * @throws java.io.IOError
587 * if an I/O error occurs obtaining the absolute path, or where a
588 * file system is constructed to access the contents of a file as
589 * a file system, and the URI of the enclosing file system cannot be
590 * obtained
591 *
592 * @throws SecurityException
593 * In the case of the default provider, and a security manager
594 * is installed, the {@link #toAbsolutePath toAbsolutePath} method
595 * throws a security exception.
596 */
597 URI toUri();
598
599 /**
600 * Returns a {@code Path} object representing the absolute path of this
601 * path.
602 *
603 * <p> If this path is already {@link Path#isAbsolute absolute} then this
604 * method simply returns this path. Otherwise, this method resolves the path
605 * in an implementation dependent manner, typically by resolving the path
606 * against a file system default directory. Depending on the implementation,
607 * this method may throw an I/O error if the file system is not accessible.
608 *
609 * @return a {@code Path} object representing the absolute path
610 *
611 * @throws java.io.IOError
612 * if an I/O error occurs
613 * @throws SecurityException
614 * In the case of the default provider, a security manager
615 * is installed, and this path is not absolute, then the security
616 * manager's {@link SecurityManager#checkPropertyAccess(String)
617 * checkPropertyAccess} method is invoked to check access to the
618 * system property {@code user.dir}
619 */
620 Path toAbsolutePath();
621
622 /**
623 * Returns the <em>real</em> path of an existing file.
624 *
625 * <p> The precise definition of this method is implementation dependent but
626 * in general it derives from this path, an {@link #isAbsolute absolute}
627 * path that locates the {@link Files#isSameFile same} file as this path, but
628 * with name elements that represent the actual name of the directories
629 * and the file. For example, where filename comparisons on a file system
630 * are case insensitive then the name elements represent the names in their
631 * actual case. Additionally, the resulting path has redundant name
632 * elements removed.
633 *
634 * <p> If this path is relative then its absolute path is first obtained,
635 * as if by invoking the {@link #toAbsolutePath toAbsolutePath} method.
636 *
637 * <p> The {@code options} array may be used to indicate how symbolic links
638 * are handled. By default, symbolic links are resolved to their final
639 * target. If the option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is
640 * present then this method does not resolve symbolic links.
641 *
642 * Some implementations allow special names such as "{@code ..}" to refer to
643 * the parent directory. When deriving the <em>real path</em>, and a
644 * "{@code ..}" (or equivalent) is preceded by a non-"{@code ..}" name then
645 * an implementation will typically cause both names to be removed. When
646 * not resolving symbolic links and the preceding name is a symbolic link
647 * then the names are only removed if it guaranteed that the resulting path
648 * will locate the same file as this path.
649 *
650 * @param options
651 * options indicating how symbolic links are handled
652 *
653 * @return an absolute path represent the <em>real</em> path of the file
654 * located by this object
655 *
656 * @throws IOException
657 * if the file does not exist or an I/O error occurs
658 * @throws SecurityException
659 * In the case of the default provider, and a security manager
660 * is installed, its {@link SecurityManager#checkRead(String) checkRead}
661 * method is invoked to check read access to the file, and where
662 * this path is not absolute, its {@link SecurityManager#checkPropertyAccess(String)
663 * checkPropertyAccess} method is invoked to check access to the
664 * system property {@code user.dir}
665 */
666 Path toRealPath(LinkOption... options) throws IOException;
667
668 /**
669 * Returns a {@link File} object representing this path. Where this {@code
670 * Path} is associated with the default provider, then this method is
671 * equivalent to returning a {@code File} object constructed with the
672 * {@code String} representation of this path.
673 *
674 * <p> If this path was created by invoking the {@code File} {@link
675 * File#toPath toPath} method then there is no guarantee that the {@code
676 * File} object returned by this method is {@link #equals equal} to the
677 * original {@code File}.
678 *
679 * @implSpec
680 * The default implementation is equivalent for this path to:
681 * <pre>{@code
682 * new File(toString());
683 * }</pre>
684 * if the {@code FileSystem} which created this {@code Path} is the default
685 * file system; otherwise an {@code UnsupportedOperationException} is
686 * thrown.
687 *
688 * @return a {@code File} object representing this path
689 *
690 * @throws UnsupportedOperationException
691 * if this {@code Path} is not associated with the default provider
692 */
693 default File toFile() {
694 if (getFileSystem() == FileSystems.getDefault()) {
695 return new File(toString());
696 } else {
697 throw new UnsupportedOperationException("Path not associated with "
698 + "default file system.");
699 }
700 }
701
702 // -- watchable --
703
704 /**
705 * Registers the file located by this path with a watch service.
706 *
707 * <p> In this release, this path locates a directory that exists. The
708 * directory is registered with the watch service so that entries in the
709 * directory can be watched. The {@code events} parameter is the events to
710 * register and may contain the following events:
711 * <ul>
712 * <li>{@link StandardWatchEventKinds#ENTRY_CREATE ENTRY_CREATE} -
713 * entry created or moved into the directory</li>
714 * <li>{@link StandardWatchEventKinds#ENTRY_DELETE ENTRY_DELETE} -
715 * entry deleted or moved out of the directory</li>
716 * <li>{@link StandardWatchEventKinds#ENTRY_MODIFY ENTRY_MODIFY} -
717 * entry in directory was modified</li>
718 * </ul>
719 *
720 * <p> The {@link WatchEvent#context context} for these events is the
721 * relative path between the directory located by this path, and the path
722 * that locates the directory entry that is created, deleted, or modified.
723 *
724 * <p> The set of events may include additional implementation specific
725 * event that are not defined by the enum {@link StandardWatchEventKinds}
726 *
727 * <p> The {@code modifiers} parameter specifies <em>modifiers</em> that
728 * qualify how the directory is registered. This release does not define any
729 * <em>standard</em> modifiers. It may contain implementation specific
730 * modifiers.
731 *
732 * <p> Where a file is registered with a watch service by means of a symbolic
733 * link then it is implementation specific if the watch continues to depend
734 * on the existence of the symbolic link after it is registered.
735 *
736 * @param watcher
737 * the watch service to which this object is to be registered
738 * @param events
739 * the events for which this object should be registered
740 * @param modifiers
741 * the modifiers, if any, that modify how the object is registered
742 *
743 * @return a key representing the registration of this object with the
744 * given watch service
745 *
746 * @throws UnsupportedOperationException
747 * if unsupported events or modifiers are specified
748 * @throws IllegalArgumentException
749 * if an invalid combination of events or modifiers is specified
750 * @throws ClosedWatchServiceException
751 * if the watch service is closed
752 * @throws NotDirectoryException
753 * if the file is registered to watch the entries in a directory
754 * and the file is not a directory <i>(optional specific exception)</i>
755 * @throws IOException
756 * if an I/O error occurs
757 * @throws SecurityException
758 * In the case of the default provider, and a security manager is
759 * installed, the {@link SecurityManager#checkRead(String) checkRead}
760 * method is invoked to check read access to the file.
761 */
762 @Override
763 WatchKey register(WatchService watcher,
764 WatchEvent.Kind<?>[] events,
765 WatchEvent.Modifier... modifiers)
766 throws IOException;
767
768 /**
769 * Registers the file located by this path with a watch service.
770 *
771 * <p> An invocation of this method behaves in exactly the same way as the
772 * invocation
773 * <pre>
774 * watchable.{@link #register(WatchService,WatchEvent.Kind[],WatchEvent.Modifier[]) register}(watcher, events, new WatchEvent.Modifier[0]);
775 * </pre>
776 *
777 * <p> <b>Usage Example:</b>
778 * Suppose we wish to register a directory for entry create, delete, and modify
779 * events:
780 * <pre>
781 * Path dir = ...
782 * WatchService watcher = ...
783 *
784 * WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
785 * </pre>
786 *
787 * @implSpec
788 * The default implementation is equivalent for this path to:
789 * <pre>{@code
790 * register(watcher, events, new WatchEvent.Modifier[0]);
791 * }</pre>
792 *
793 * @param watcher
794 * The watch service to which this object is to be registered
795 * @param events
796 * The events for which this object should be registered
797 *
798 * @return A key representing the registration of this object with the
799 * given watch service
800 *
801 * @throws UnsupportedOperationException
802 * If unsupported events are specified
803 * @throws IllegalArgumentException
804 * If an invalid combination of events is specified
805 * @throws ClosedWatchServiceException
806 * If the watch service is closed
807 * @throws NotDirectoryException
808 * If the file is registered to watch the entries in a directory
809 * and the file is not a directory <i>(optional specific exception)</i>
810 * @throws IOException
811 * If an I/O error occurs
812 * @throws SecurityException
813 * In the case of the default provider, and a security manager is
814 * installed, the {@link SecurityManager#checkRead(String) checkRead}
815 * method is invoked to check read access to the file.
816 */
817 @Override
818 default WatchKey register(WatchService watcher,
819 WatchEvent.Kind<?>... events) throws IOException {
820 return register(watcher, events, new WatchEvent.Modifier[0]);
821 }
822
823 // -- Iterable --
824
825 /**
826 * Returns an iterator over the name elements of this path.
827 *
828 * <p> The first element returned by the iterator represents the name
829 * element that is closest to the root in the directory hierarchy, the
830 * second element is the next closest, and so on. The last element returned
831 * is the name of the file or directory denoted by this path. The {@link
832 * #getRoot root} component, if present, is not returned by the iterator.
833 *
834 * @implSpec
835 * The default implementation returns an {@code Iterator<Path>} which, for
836 * this path, traverses the {@code Path}s returned by
837 * {@code getName(index)}, where {@code index} ranges from zero to
838 * {@code getNameCount() - 1}, inclusive.
839 *
840 * @return an iterator over the name elements of this path.
841 */
842 @Override
843 default Iterator<Path> iterator() {
844 return new Iterator<>() {
845 private int i = 0;
846
847 @Override
848 public boolean hasNext() {
849 return (i < getNameCount());
850 }
851
852 @Override
853 public Path next() {
854 if (i < getNameCount()) {
855 Path result = getName(i);
856 i++;
857 return result;
858 } else {
859 throw new NoSuchElementException();
860 }
861 }
862 };
863 }
864
865 // -- compareTo/equals/hashCode --
866
867 /**
868 * Compares two abstract paths lexicographically. The ordering defined by
869 * this method is provider specific, and in the case of the default
870 * provider, platform specific. This method does not access the file system
871 * and neither file is required to exist.
872 *
873 * <p> This method may not be used to compare paths that are associated
874 * with different file system providers.
875 *
876 * @param other the path compared to this path.
877 *
878 * @return zero if the argument is {@link #equals equal} to this path, a
879 * value less than zero if this path is lexicographically less than
880 * the argument, or a value greater than zero if this path is
881 * lexicographically greater than the argument
882 *
883 * @throws ClassCastException
884 * if the paths are associated with different providers
885 */
886 @Override
887 int compareTo(Path other);
888
889 /**
890 * Tests this path for equality with the given object.
891 *
892 * <p> If the given object is not a Path, or is a Path associated with a
893 * different {@code FileSystem}, then this method returns {@code false}.
894 *
895 * <p> Whether or not two path are equal depends on the file system
896 * implementation. In some cases the paths are compared without regard
897 * to case, and others are case sensitive. This method does not access the
898 * file system and the file is not required to exist. Where required, the
899 * {@link Files#isSameFile isSameFile} method may be used to check if two
900 * paths locate the same file.
901 *
902 * <p> This method satisfies the general contract of the {@link
903 * java.lang.Object#equals(Object) Object.equals} method. </p>
904 *
905 * @param other
906 * the object to which this object is to be compared
907 *
908 * @return {@code true} if, and only if, the given object is a {@code Path}
909 * that is identical to this {@code Path}
910 */
911 boolean equals(Object other);
912
913 /**
914 * Computes a hash code for this path.
915 *
916 * <p> The hash code is based upon the components of the path, and
917 * satisfies the general contract of the {@link Object#hashCode
918 * Object.hashCode} method.
919 *
920 * @return the hash-code value for this path
921 */
922 int hashCode();
923
924 /**
925 * Returns the string representation of this path.
926 *
927 * <p> If this path was created by converting a path string using the
928 * {@link FileSystem#getPath getPath} method then the path string returned
929 * by this method may differ from the original String used to create the path.
930 *
931 * <p> The returned path string uses the default name {@link
932 * FileSystem#getSeparator separator} to separate names in the path.
933 *
934 * @return the string representation of this path
935 */
936 String toString();
937 }