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
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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
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. The <em>extension</em> of a {@code Path} is defined to be the
49 * portion of the path after but not including the last dot ({@code '.'}) and
50 * is part of the name element farthest from the root. {@code Path} defines the
51 * {@link #getFileName() getFileName}, {@link #getParent getParent},
52 * {@link #getRoot getRoot}, {@link #getExtension getExtension}, and
53 * {@link #subpath subpath} methods to access the path components or a
54 * subsequence of its name elements.
55 *
56 * <p> In addition to accessing the components of a path, a {@code Path} also
57 * defines the {@link #resolve(Path) resolve} and {@link #resolveSibling(Path)
58 * resolveSibling} methods to combine paths. The {@link #relativize relativize}
59 * method that can be used to construct a relative path between two paths.
60 * Paths can be {@link #compareTo compared}, and tested against each other using
61 * the {@link #startsWith startsWith} and {@link #endsWith endsWith} methods.
62 *
63 * <p> This interface extends {@link Watchable} interface so that a directory
64 * located by a path can be {@link #register registered} with a {@link
65 * WatchService} and entries in the directory watched. </p>
66 *
67 * <p> <b>WARNING:</b> This interface is only intended to be implemented by
68 * those developing custom file system implementations. Methods may be added to
69 * this interface in future releases. </p>
70 *
71 * <h2>Accessing Files</h2>
72 * <p> Paths may be used with the {@link Files} class to operate on files,
73 * directories, and other types of files. For example, suppose we want a {@link
74 * java.io.BufferedReader} to read text from a file "{@code access.log}". The
75 * file is located in a directory "{@code logs}" relative to the current working
76 * directory and is UTF-8 encoded.
77 * <pre>
78 * Path path = FileSystems.getDefault().getPath("logs", "access.log");
79 * BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8);
80 * </pre>
81 *
82 * <a id="interop"></a><h2>Interoperability</h2>
83 * <p> Paths associated with the default {@link
84 * java.nio.file.spi.FileSystemProvider provider} are generally interoperable
85 * with the {@link java.io.File java.io.File} class. Paths created by other
86 * providers are unlikely to be interoperable with the abstract path names
87 * represented by {@code java.io.File}. The {@link java.io.File#toPath toPath}
88 * method may be used to obtain a {@code Path} from the abstract path name
89 * represented by a {@code java.io.File} object. The resulting {@code Path} can
90 * be used to operate on the same file as the {@code java.io.File} object. In
91 * addition, the {@link #toFile toFile} method is useful to construct a {@code
92 * File} from the {@code String} representation of a {@code Path}.
93 *
94 * <h2>Concurrency</h2>
95 * <p> Implementations of this interface are immutable and safe for use by
96 * multiple concurrent threads.
97 *
98 * @since 1.7
99 * @see Paths
100 */
101
102 public interface Path
103 extends Comparable<Path>, Iterable<Path>, Watchable
104 {
105 /**
106 * Returns the file system that created this object.
107 *
108 * @return the file system that created this object
109 */
110 FileSystem getFileSystem();
111
112 /**
113 * Tells whether or not this path is absolute.
114 *
115 * <p> An absolute path is complete in that it doesn't need to be combined
116 * with other path information in order to locate a file.
117 *
118 * @return {@code true} if, and only if, this path is absolute
119 */
120 boolean isAbsolute();
121
122 /**
123 * Returns the root component of this path as a {@code Path} object,
124 * or {@code null} if this path does not have a root component.
125 *
126 * @return a path representing the root component of this path,
127 * or {@code null}
128 */
129 Path getRoot();
130
131 /**
132 * Returns the name of the file or directory denoted by this path as a
133 * {@code Path} object. The file name is the <em>farthest</em> element from
134 * the root in the directory hierarchy.
135 *
136 * @return a path representing the name of the file or directory, or
137 * {@code null} if this path has zero elements
138 */
139 Path getFileName();
140
141 /**
142 * Returns the <em>parent path</em>, or {@code null} if this path does not
143 * have a parent.
144 *
145 * <p> The parent of this path object consists of this path's root
146 * component, if any, and each element in the path except for the
147 * <em>farthest</em> from the root in the directory hierarchy. This method
148 * does not access the file system; the path or its parent may not exist.
149 * Furthermore, this method does not eliminate special names such as "."
150 * and ".." that may be used in some implementations. On UNIX for example,
151 * the parent of "{@code /a/b/c}" is "{@code /a/b}", and the parent of
152 * {@code "x/y/.}" is "{@code x/y}". This method may be used with the {@link
153 * #normalize normalize} method, to eliminate redundant names, for cases where
154 * <em>shell-like</em> navigation is required.
155 *
156 * <p> If this path has more than one element, and no root component, then
157 * this method is equivalent to evaluating the expression:
158 * <blockquote><pre>
159 * subpath(0, getNameCount()-1);
160 * </pre></blockquote>
161 *
162 * @return a path representing the path's parent
163 */
164 Path getParent();
165
166 /**
167 * Returns the extension of this {@code Path} as a {@code String}.
168 * The extension is that portion of the path after the last dot
169 * ({@code '.'}). If this path is empty, does not contain a dot, ends
170 * with a dot, or has a {@link FileSystem#getSeparator() name-separator}
171 * after the last dot, then this method returns an empty {@code String}.
172 *
173 * @implSpec
174 * For the cases where a non-empty string would be returned, the default
175 * implementation is equivalent for this path to:
176 * <pre>{@code
177 * toString().substring(toString().lastIndexOf(".") + 1);
178 * }</pre>
179 *
180 * @return the extension of this path or an empty {@code String}
181 *
182 * @since 11
183 */
184 default String getExtension() {
185 String path = toString();
186
187 int lastDot = path.lastIndexOf(".");
188 if (lastDot == -1 || lastDot == path.length() - 1 ||
189 path.indexOf(getFileSystem().getSeparator(), lastDot + 1) != -1) {
190 return "";
191 }
192
193 return path.substring(lastDot + 1);
194 }
195
196 /**
197 * Returns the number of name elements in the path.
198 *
199 * @return the number of elements in the path, or {@code 0} if this path
200 * only represents a root component
201 */
202 int getNameCount();
203
204 /**
205 * Returns a name element of this path as a {@code Path} object.
206 *
207 * <p> The {@code index} parameter is the index of the name element to return.
208 * The element that is <em>closest</em> to the root in the directory hierarchy
209 * has index {@code 0}. The element that is <em>farthest</em> from the root
210 * has index {@link #getNameCount count}{@code -1}.
211 *
212 * @param index
213 * the index of the element
214 *
215 * @return the name element
216 *
217 * @throws IllegalArgumentException
218 * if {@code index} is negative, {@code index} is greater than or
219 * equal to the number of elements, or this path has zero name
220 * elements
221 */
222 Path getName(int index);
223
224 /**
225 * Returns a relative {@code Path} that is a subsequence of the name
226 * elements of this path.
227 *
228 * <p> The {@code beginIndex} and {@code endIndex} parameters specify the
229 * subsequence of name elements. The name that is <em>closest</em> to the root
230 * in the directory hierarchy has index {@code 0}. The name that is
231 * <em>farthest</em> from the root has index {@link #getNameCount
232 * count}{@code -1}. The returned {@code Path} object has the name elements
233 * that begin at {@code beginIndex} and extend to the element at index {@code
234 * endIndex-1}.
235 *
236 * @param beginIndex
237 * the index of the first element, inclusive
238 * @param endIndex
239 * the index of the last element, exclusive
240 *
241 * @return a new {@code Path} object that is a subsequence of the name
242 * elements in this {@code Path}
243 *
244 * @throws IllegalArgumentException
245 * if {@code beginIndex} is negative, or greater than or equal to
246 * the number of elements. If {@code endIndex} is less than or
247 * equal to {@code beginIndex}, or larger than the number of elements.
248 */
249 Path subpath(int beginIndex, int endIndex);
250
251 /**
252 * Tests if this path starts with the given path.
253 *
254 * <p> This path <em>starts</em> with the given path if this path's root
255 * component <em>starts</em> with the root component of the given path,
256 * and this path starts with the same name elements as the given path.
257 * If the given path has more name elements than this path then {@code false}
258 * is returned.
259 *
260 * <p> Whether or not the root component of this path starts with the root
261 * component of the given path is file system specific. If this path does
262 * not have a root component and the given path has a root component then
263 * this path does not start with the given path.
264 *
265 * <p> If the given path is associated with a different {@code FileSystem}
266 * to this path then {@code false} is returned.
267 *
268 * @param other
269 * the given path
270 *
271 * @return {@code true} if this path starts with the given path; otherwise
272 * {@code false}
273 */
274 boolean startsWith(Path other);
275
276 /**
277 * Tests if this path starts with a {@code Path}, constructed by converting
278 * the given path string, in exactly the manner specified by the {@link
279 * #startsWith(Path) startsWith(Path)} method. On UNIX for example, the path
280 * "{@code foo/bar}" starts with "{@code foo}" and "{@code foo/bar}". It
281 * does not start with "{@code f}" or "{@code fo}".
282 *
283 * @implSpec
284 * The default implementation is equivalent for this path to:
285 * <pre>{@code
286 * startsWith(getFileSystem().getPath(other));
287 * }</pre>
288 *
289 * @param other
290 * the given path string
291 *
292 * @return {@code true} if this path starts with the given path; otherwise
293 * {@code false}
294 *
295 * @throws InvalidPathException
296 * If the path string cannot be converted to a Path.
297 */
298 default boolean startsWith(String other) {
299 return startsWith(getFileSystem().getPath(other));
300 }
301
302 /**
303 * Tests if this path ends with the given path.
304 *
305 * <p> If the given path has <em>N</em> elements, and no root component,
306 * and this path has <em>N</em> or more elements, then this path ends with
307 * the given path if the last <em>N</em> elements of each path, starting at
308 * the element farthest from the root, are equal.
309 *
310 * <p> If the given path has a root component then this path ends with the
311 * given path if the root component of this path <em>ends with</em> the root
312 * component of the given path, and the corresponding elements of both paths
313 * are equal. Whether or not the root component of this path ends with the
314 * root component of the given path is file system specific. If this path
315 * does not have a root component and the given path has a root component
316 * then this path does not end with the given path.
317 *
318 * <p> If the given path is associated with a different {@code FileSystem}
319 * to this path then {@code false} is returned.
320 *
321 * @param other
322 * the given path
323 *
324 * @return {@code true} if this path ends with the given path; otherwise
325 * {@code false}
326 */
327 boolean endsWith(Path other);
328
329 /**
330 * Tests if this path ends with a {@code Path}, constructed by converting
331 * the given path string, in exactly the manner specified by the {@link
332 * #endsWith(Path) endsWith(Path)} method. On UNIX for example, the path
333 * "{@code foo/bar}" ends with "{@code foo/bar}" and "{@code bar}". It does
334 * not end with "{@code r}" or "{@code /bar}". Note that trailing separators
335 * are not taken into account, and so invoking this method on the {@code
336 * Path}"{@code foo/bar}" with the {@code String} "{@code bar/}" returns
337 * {@code true}.
338 *
339 * @implSpec
340 * The default implementation is equivalent for this path to:
341 * <pre>{@code
342 * endsWith(getFileSystem().getPath(other));
343 * }</pre>
344 *
345 * @param other
346 * the given path string
347 *
348 * @return {@code true} if this path ends with the given path; otherwise
349 * {@code false}
350 *
351 * @throws InvalidPathException
352 * If the path string cannot be converted to a Path.
353 */
354 default boolean endsWith(String other) {
355 return endsWith(getFileSystem().getPath(other));
356 }
357
358 /**
359 * Returns a path that is this path with redundant name elements eliminated.
360 *
361 * <p> The precise definition of this method is implementation dependent but
362 * in general it derives from this path, a path that does not contain
363 * <em>redundant</em> name elements. In many file systems, the "{@code .}"
364 * and "{@code ..}" are special names used to indicate the current directory
365 * and parent directory. In such file systems all occurrences of "{@code .}"
366 * are considered redundant. If a "{@code ..}" is preceded by a
367 * non-"{@code ..}" name then both names are considered redundant (the
368 * process to identify such names is repeated until it is no longer
369 * applicable).
370 *
371 * <p> This method does not access the file system; the path may not locate
372 * a file that exists. Eliminating "{@code ..}" and a preceding name from a
373 * path may result in the path that locates a different file than the original
374 * path. This can arise when the preceding name is a symbolic link.
375 *
376 * @return the resulting path or this path if it does not contain
377 * redundant name elements; an empty path is returned if this path
378 * does not have a root component and all name elements are redundant
379 *
380 * @see #getParent
381 * @see #toRealPath
382 */
383 Path normalize();
384
385 // -- resolution and relativization --
386
387 /**
388 * Resolve the given path against this path.
389 *
390 * <p> If the {@code other} parameter is an {@link #isAbsolute() absolute}
391 * path then this method trivially returns {@code other}. If {@code other}
392 * is an <i>empty path</i> then this method trivially returns this path.
393 * Otherwise this method considers this path to be a directory and resolves
394 * the given path against this path. In the simplest case, the given path
395 * does not have a {@link #getRoot root} component, in which case this method
396 * <em>joins</em> the given path to this path and returns a resulting path
397 * that {@link #endsWith ends} with the given path. Where the given path has
398 * a root component then resolution is highly implementation dependent and
399 * therefore unspecified.
400 *
401 * @param other
402 * the path to resolve against this path
403 *
404 * @return the resulting path
405 *
406 * @see #relativize
407 */
408 Path resolve(Path other);
409
410 /**
411 * Converts a given path string to a {@code Path} and resolves it against
412 * this {@code Path} in exactly the manner specified by the {@link
413 * #resolve(Path) resolve} method. For example, suppose that the name
414 * separator is "{@code /}" and a path represents "{@code foo/bar}", then
415 * invoking this method with the path string "{@code gus}" will result in
416 * the {@code Path} "{@code foo/bar/gus}".
417 *
418 * @implSpec
419 * The default implementation is equivalent for this path to:
420 * <pre>{@code
421 * resolve(getFileSystem().getPath(other));
422 * }</pre>
423 *
424 * @param other
425 * the path string to resolve against this path
426 *
427 * @return the resulting path
428 *
429 * @throws InvalidPathException
430 * if the path string cannot be converted to a Path.
431 *
432 * @see FileSystem#getPath
433 */
434 default Path resolve(String other) {
435 return resolve(getFileSystem().getPath(other));
436 }
437
438 /**
439 * Resolves the given path against this path's {@link #getParent parent}
440 * path. This is useful where a file name needs to be <i>replaced</i> with
441 * another file name. For example, suppose that the name separator is
442 * "{@code /}" and a path represents "{@code dir1/dir2/foo}", then invoking
443 * this method with the {@code Path} "{@code bar}" will result in the {@code
444 * Path} "{@code dir1/dir2/bar}". If this path does not have a parent path,
445 * or {@code other} is {@link #isAbsolute() absolute}, then this method
446 * returns {@code other}. If {@code other} is an empty path then this method
447 * returns this path's parent, or where this path doesn't have a parent, the
448 * empty path.
449 *
450 * @implSpec
451 * The default implementation is equivalent for this path to:
452 * <pre>{@code
453 * (getParent() == null) ? other : getParent().resolve(other);
454 * }</pre>
455 * unless {@code other == null}, in which case a
456 * {@code NullPointerException} is thrown.
457 *
458 * @param other
459 * the path to resolve against this path's parent
460 *
461 * @return the resulting path
462 *
463 * @see #resolve(Path)
464 */
465 default Path resolveSibling(Path other) {
466 if (other == null)
467 throw new NullPointerException();
468 Path parent = getParent();
469 return (parent == null) ? other : parent.resolve(other);
470 }
471
472 /**
473 * Converts a given path string to a {@code Path} and resolves it against
474 * this path's {@link #getParent parent} path in exactly the manner
475 * specified by the {@link #resolveSibling(Path) resolveSibling} method.
476 *
477 * @implSpec
478 * The default implementation is equivalent for this path to:
479 * <pre>{@code
480 * resolveSibling(getFileSystem().getPath(other));
481 * }</pre>
482 *
483 * @param other
484 * the path string to resolve against this path's parent
485 *
486 * @return the resulting path
487 *
488 * @throws InvalidPathException
489 * if the path string cannot be converted to a Path.
490 *
491 * @see FileSystem#getPath
492 */
493 default Path resolveSibling(String other) {
494 return resolveSibling(getFileSystem().getPath(other));
495 }
496
497 /**
498 * Constructs a relative path between this path and a given path.
499 *
500 * <p> Relativization is the inverse of {@link #resolve(Path) resolution}.
501 * This method attempts to construct a {@link #isAbsolute relative} path
502 * that when {@link #resolve(Path) resolved} against this path, yields a
503 * path that locates the same file as the given path. For example, on UNIX,
504 * if this path is {@code "/a/b"} and the given path is {@code "/a/b/c/d"}
505 * then the resulting relative path would be {@code "c/d"}. Where this
506 * path and the given path do not have a {@link #getRoot root} component,
507 * then a relative path can be constructed. A relative path cannot be
508 * constructed if only one of the paths have a root component. Where both
509 * paths have a root component then it is implementation dependent if a
510 * relative path can be constructed. If this path and the given path are
511 * {@link #equals equal} then an <i>empty path</i> is returned.
512 *
513 * <p> For any two {@link #normalize normalized} paths <i>p</i> and
514 * <i>q</i>, where <i>q</i> does not have a root component,
515 * <blockquote>
516 * <i>p</i>{@code .relativize(}<i>p</i>
517 * {@code .resolve(}<i>q</i>{@code )).equals(}<i>q</i>{@code )}
518 * </blockquote>
519 *
520 * <p> When symbolic links are supported, then whether the resulting path,
521 * when resolved against this path, yields a path that can be used to locate
522 * the {@link Files#isSameFile same} file as {@code other} is implementation
523 * dependent. For example, if this path is {@code "/a/b"} and the given
524 * path is {@code "/a/x"} then the resulting relative path may be {@code
525 * "../x"}. If {@code "b"} is a symbolic link then is implementation
526 * dependent if {@code "a/b/../x"} would locate the same file as {@code "/a/x"}.
527 *
528 * @param other
529 * the path to relativize against this path
530 *
531 * @return the resulting relative path, or an empty path if both paths are
532 * equal
533 *
534 * @throws IllegalArgumentException
535 * if {@code other} is not a {@code Path} that can be relativized
536 * against this path
537 */
538 Path relativize(Path other);
539
540 /**
541 * Returns a URI to represent this path.
542 *
543 * <p> This method constructs an absolute {@link URI} with a {@link
544 * URI#getScheme() scheme} equal to the URI scheme that identifies the
545 * provider. The exact form of the scheme specific part is highly provider
546 * dependent.
547 *
548 * <p> In the case of the default provider, the URI is hierarchical with
549 * a {@link URI#getPath() path} component that is absolute. The query and
550 * fragment components are undefined. Whether the authority component is
551 * defined or not is implementation dependent. There is no guarantee that
552 * the {@code URI} may be used to construct a {@link java.io.File java.io.File}.
553 * In particular, if this path represents a Universal Naming Convention (UNC)
554 * path, then the UNC server name may be encoded in the authority component
555 * of the resulting URI. In the case of the default provider, and the file
556 * exists, and it can be determined that the file is a directory, then the
557 * resulting {@code URI} will end with a slash.
558 *
559 * <p> The default provider provides a similar <em>round-trip</em> guarantee
560 * to the {@link java.io.File} class. For a given {@code Path} <i>p</i> it
561 * is guaranteed that
562 * <blockquote>
563 * {@link Paths#get(URI) Paths.get}{@code (}<i>p</i>{@code .toUri()).equals(}<i>p</i>
564 * {@code .}{@link #toAbsolutePath() toAbsolutePath}{@code ())}
565 * </blockquote>
566 * so long as the original {@code Path}, the {@code URI}, and the new {@code
567 * Path} are all created in (possibly different invocations of) the same
568 * Java virtual machine. Whether other providers make any guarantees is
569 * provider specific and therefore unspecified.
570 *
571 * <p> When a file system is constructed to access the contents of a file
572 * as a file system then it is highly implementation specific if the returned
573 * URI represents the given path in the file system or it represents a
574 * <em>compound</em> URI that encodes the URI of the enclosing file system.
575 * A format for compound URIs is not defined in this release; such a scheme
576 * may be added in a future release.
577 *
578 * @return the URI representing this path
579 *
580 * @throws java.io.IOError
581 * if an I/O error occurs obtaining the absolute path, or where a
582 * file system is constructed to access the contents of a file as
583 * a file system, and the URI of the enclosing file system cannot be
584 * obtained
585 *
586 * @throws SecurityException
587 * In the case of the default provider, and a security manager
588 * is installed, the {@link #toAbsolutePath toAbsolutePath} method
589 * throws a security exception.
590 */
591 URI toUri();
592
593 /**
594 * Returns a {@code Path} object representing the absolute path of this
595 * path.
596 *
597 * <p> If this path is already {@link Path#isAbsolute absolute} then this
598 * method simply returns this path. Otherwise, this method resolves the path
599 * in an implementation dependent manner, typically by resolving the path
600 * against a file system default directory. Depending on the implementation,
601 * this method may throw an I/O error if the file system is not accessible.
602 *
603 * @return a {@code Path} object representing the absolute path
604 *
605 * @throws java.io.IOError
606 * if an I/O error occurs
607 * @throws SecurityException
608 * In the case of the default provider, a security manager
609 * is installed, and this path is not absolute, then the security
610 * manager's {@link SecurityManager#checkPropertyAccess(String)
611 * checkPropertyAccess} method is invoked to check access to the
612 * system property {@code user.dir}
613 */
614 Path toAbsolutePath();
615
616 /**
617 * Returns the <em>real</em> path of an existing file.
618 *
619 * <p> The precise definition of this method is implementation dependent but
620 * in general it derives from this path, an {@link #isAbsolute absolute}
621 * path that locates the {@link Files#isSameFile same} file as this path, but
622 * with name elements that represent the actual name of the directories
623 * and the file. For example, where filename comparisons on a file system
624 * are case insensitive then the name elements represent the names in their
625 * actual case. Additionally, the resulting path has redundant name
626 * elements removed.
627 *
628 * <p> If this path is relative then its absolute path is first obtained,
629 * as if by invoking the {@link #toAbsolutePath toAbsolutePath} method.
630 *
631 * <p> The {@code options} array may be used to indicate how symbolic links
632 * are handled. By default, symbolic links are resolved to their final
633 * target. If the option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is
634 * present then this method does not resolve symbolic links.
635 *
636 * Some implementations allow special names such as "{@code ..}" to refer to
637 * the parent directory. When deriving the <em>real path</em>, and a
638 * "{@code ..}" (or equivalent) is preceded by a non-"{@code ..}" name then
639 * an implementation will typically cause both names to be removed. When
640 * not resolving symbolic links and the preceding name is a symbolic link
641 * then the names are only removed if it guaranteed that the resulting path
642 * will locate the same file as this path.
643 *
644 * @param options
645 * options indicating how symbolic links are handled
646 *
647 * @return an absolute path represent the <em>real</em> path of the file
648 * located by this object
649 *
650 * @throws IOException
651 * if the file does not exist or an I/O error occurs
652 * @throws SecurityException
653 * In the case of the default provider, and a security manager
654 * is installed, its {@link SecurityManager#checkRead(String) checkRead}
655 * method is invoked to check read access to the file, and where
656 * this path is not absolute, its {@link SecurityManager#checkPropertyAccess(String)
657 * checkPropertyAccess} method is invoked to check access to the
658 * system property {@code user.dir}
659 */
660 Path toRealPath(LinkOption... options) throws IOException;
661
662 /**
663 * Returns a {@link File} object representing this path. Where this {@code
664 * Path} is associated with the default provider, then this method is
665 * equivalent to returning a {@code File} object constructed with the
666 * {@code String} representation of this path.
667 *
668 * <p> If this path was created by invoking the {@code File} {@link
669 * File#toPath toPath} method then there is no guarantee that the {@code
670 * File} object returned by this method is {@link #equals equal} to the
671 * original {@code File}.
672 *
673 * @implSpec
674 * The default implementation is equivalent for this path to:
675 * <pre>{@code
676 * new File(toString());
677 * }</pre>
678 * if the {@code FileSystem} which created this {@code Path} is the default
679 * file system; otherwise an {@code UnsupportedOperationException} is
680 * thrown.
681 *
682 * @return a {@code File} object representing this path
683 *
684 * @throws UnsupportedOperationException
685 * if this {@code Path} is not associated with the default provider
686 */
687 default File toFile() {
688 if (getFileSystem() == FileSystems.getDefault()) {
689 return new File(toString());
690 } else {
691 throw new UnsupportedOperationException("Path not associated with "
692 + "default file system.");
693 }
694 }
695
696 // -- watchable --
697
698 /**
699 * Registers the file located by this path with a watch service.
700 *
701 * <p> In this release, this path locates a directory that exists. The
702 * directory is registered with the watch service so that entries in the
703 * directory can be watched. The {@code events} parameter is the events to
704 * register and may contain the following events:
705 * <ul>
706 * <li>{@link StandardWatchEventKinds#ENTRY_CREATE ENTRY_CREATE} -
707 * entry created or moved into the directory</li>
708 * <li>{@link StandardWatchEventKinds#ENTRY_DELETE ENTRY_DELETE} -
709 * entry deleted or moved out of the directory</li>
710 * <li>{@link StandardWatchEventKinds#ENTRY_MODIFY ENTRY_MODIFY} -
711 * entry in directory was modified</li>
712 * </ul>
713 *
714 * <p> The {@link WatchEvent#context context} for these events is the
715 * relative path between the directory located by this path, and the path
716 * that locates the directory entry that is created, deleted, or modified.
717 *
718 * <p> The set of events may include additional implementation specific
719 * event that are not defined by the enum {@link StandardWatchEventKinds}
720 *
721 * <p> The {@code modifiers} parameter specifies <em>modifiers</em> that
722 * qualify how the directory is registered. This release does not define any
723 * <em>standard</em> modifiers. It may contain implementation specific
724 * modifiers.
725 *
726 * <p> Where a file is registered with a watch service by means of a symbolic
727 * link then it is implementation specific if the watch continues to depend
728 * on the existence of the symbolic link after it is registered.
729 *
730 * @param watcher
731 * the watch service to which this object is to be registered
732 * @param events
733 * the events for which this object should be registered
734 * @param modifiers
735 * the modifiers, if any, that modify how the object is registered
736 *
737 * @return a key representing the registration of this object with the
738 * given watch service
739 *
740 * @throws UnsupportedOperationException
741 * if unsupported events or modifiers are specified
742 * @throws IllegalArgumentException
743 * if an invalid combination of events or modifiers is specified
744 * @throws ClosedWatchServiceException
745 * if the watch service is closed
746 * @throws NotDirectoryException
747 * if the file is registered to watch the entries in a directory
748 * and the file is not a directory <i>(optional specific exception)</i>
749 * @throws IOException
750 * if an I/O error occurs
751 * @throws SecurityException
752 * In the case of the default provider, and a security manager is
753 * installed, the {@link SecurityManager#checkRead(String) checkRead}
754 * method is invoked to check read access to the file.
755 */
756 @Override
757 WatchKey register(WatchService watcher,
758 WatchEvent.Kind<?>[] events,
759 WatchEvent.Modifier... modifiers)
760 throws IOException;
761
762 /**
763 * Registers the file located by this path with a watch service.
764 *
765 * <p> An invocation of this method behaves in exactly the same way as the
766 * invocation
767 * <pre>
768 * watchable.{@link #register(WatchService,WatchEvent.Kind[],WatchEvent.Modifier[]) register}(watcher, events, new WatchEvent.Modifier[0]);
769 * </pre>
770 *
771 * <p> <b>Usage Example:</b>
772 * Suppose we wish to register a directory for entry create, delete, and modify
773 * events:
774 * <pre>
775 * Path dir = ...
776 * WatchService watcher = ...
777 *
778 * WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
779 * </pre>
780 *
781 * @implSpec
782 * The default implementation is equivalent for this path to:
783 * <pre>{@code
784 * register(watcher, events, new WatchEvent.Modifier[0]);
785 * }</pre>
786 *
787 * @param watcher
788 * The watch service to which this object is to be registered
789 * @param events
790 * The events for which this object should be registered
791 *
792 * @return A key representing the registration of this object with the
793 * given watch service
794 *
795 * @throws UnsupportedOperationException
796 * If unsupported events are specified
797 * @throws IllegalArgumentException
798 * If an invalid combination of events is specified
799 * @throws ClosedWatchServiceException
800 * If the watch service is closed
801 * @throws NotDirectoryException
802 * If the file is registered to watch the entries in a directory
803 * and the file is not a directory <i>(optional specific exception)</i>
804 * @throws IOException
805 * If an I/O error occurs
806 * @throws SecurityException
807 * In the case of the default provider, and a security manager is
808 * installed, the {@link SecurityManager#checkRead(String) checkRead}
809 * method is invoked to check read access to the file.
810 */
811 @Override
812 default WatchKey register(WatchService watcher,
813 WatchEvent.Kind<?>... events) throws IOException {
814 return register(watcher, events, new WatchEvent.Modifier[0]);
815 }
816
817 // -- Iterable --
818
819 /**
820 * Returns an iterator over the name elements of this path.
821 *
822 * <p> The first element returned by the iterator represents the name
823 * element that is closest to the root in the directory hierarchy, the
824 * second element is the next closest, and so on. The last element returned
825 * is the name of the file or directory denoted by this path. The {@link
826 * #getRoot root} component, if present, is not returned by the iterator.
827 *
828 * @implSpec
829 * The default implementation returns an {@code Iterator<Path>} which, for
830 * this path, traverses the {@code Path}s returned by
831 * {@code getName(index)}, where {@code index} ranges from zero to
832 * {@code getNameCount() - 1}, inclusive.
833 *
834 * @return an iterator over the name elements of this path.
835 */
836 @Override
837 default Iterator<Path> iterator() {
838 return new Iterator<>() {
839 private int i = 0;
840
841 @Override
842 public boolean hasNext() {
843 return (i < getNameCount());
844 }
845
846 @Override
847 public Path next() {
848 if (i < getNameCount()) {
849 Path result = getName(i);
850 i++;
851 return result;
852 } else {
853 throw new NoSuchElementException();
854 }
855 }
856 };
857 }
858
859 // -- compareTo/equals/hashCode --
860
861 /**
862 * Compares two abstract paths lexicographically. The ordering defined by
863 * this method is provider specific, and in the case of the default
864 * provider, platform specific. This method does not access the file system
865 * and neither file is required to exist.
866 *
867 * <p> This method may not be used to compare paths that are associated
868 * with different file system providers.
869 *
870 * @param other the path compared to this path.
871 *
872 * @return zero if the argument is {@link #equals equal} to this path, a
873 * value less than zero if this path is lexicographically less than
874 * the argument, or a value greater than zero if this path is
875 * lexicographically greater than the argument
876 *
877 * @throws ClassCastException
878 * if the paths are associated with different providers
879 */
880 @Override
881 int compareTo(Path other);
882
883 /**
884 * Tests this path for equality with the given object.
885 *
886 * <p> If the given object is not a Path, or is a Path associated with a
887 * different {@code FileSystem}, then this method returns {@code false}.
888 *
889 * <p> Whether or not two path are equal depends on the file system
890 * implementation. In some cases the paths are compared without regard
891 * to case, and others are case sensitive. This method does not access the
892 * file system and the file is not required to exist. Where required, the
893 * {@link Files#isSameFile isSameFile} method may be used to check if two
894 * paths locate the same file.
895 *
896 * <p> This method satisfies the general contract of the {@link
897 * java.lang.Object#equals(Object) Object.equals} method. </p>
898 *
899 * @param other
900 * the object to which this object is to be compared
901 *
902 * @return {@code true} if, and only if, the given object is a {@code Path}
903 * that is identical to this {@code Path}
904 */
905 boolean equals(Object other);
906
907 /**
908 * Computes a hash code for this path.
909 *
910 * <p> The hash code is based upon the components of the path, and
911 * satisfies the general contract of the {@link Object#hashCode
912 * Object.hashCode} method.
913 *
914 * @return the hash-code value for this path
915 */
916 int hashCode();
917
918 /**
919 * Returns the string representation of this path.
920 *
921 * <p> If this path was created by converting a path string using the
922 * {@link FileSystem#getPath getPath} method then the path string returned
923 * by this method may differ from the original String used to create the path.
924 *
925 * <p> The returned path string uses the default name {@link
926 * FileSystem#getSeparator separator} to separate names in the path.
927 *
928 * @return the string representation of this path
929 */
930 String toString();
931 }