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
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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.nio.file.spi.FileSystemProvider;
32 import java.util.Iterator;
33 import java.util.NoSuchElementException;
34
35 /**
36 * An object that may be used to locate a file in a file system. It will
37 * typically represent a system dependent file path.
38 *
39 * <p> A {@code Path} represents a path that is hierarchical and composed of a
40 * sequence of directory and file name elements separated by a special separator
41 * or delimiter. A <em>root component</em>, that identifies a file system
42 * hierarchy, may also be present. The name element that is <em>farthest</em>
43 * from the root of the directory hierarchy is the name of a file or directory.
44 * The other name elements are directory names. A {@code Path} can represent a
45 * root, a root and a sequence of names, or simply one or more name elements.
46 * A {@code Path} is considered to be an <i>empty path</i> if it consists
47 * solely of one name element that is empty. Accessing a file using an
48 * <i>empty path</i> is equivalent to accessing the default directory of the
49 * file system. {@code Path} defines the {@link #getFileName() getFileName},
50 * {@link #getParent getParent}, {@link #getRoot getRoot}, and {@link #subpath
51 * subpath} methods to access the path components or a subsequence of its name
52 * elements.
53 *
54 * <p> In addition to accessing the components of a path, a {@code Path} also
55 * defines the {@link #resolve(Path) resolve} and {@link #resolveSibling(Path)
56 * resolveSibling} methods to combine paths. The {@link #relativize relativize}
57 * method that can be used to construct a relative path between two paths.
58 * Paths can be {@link #compareTo compared}, and tested against each other using
59 * the {@link #startsWith startsWith} and {@link #endsWith endsWith} methods.
60 *
61 * <p> This interface extends {@link Watchable} interface so that a directory
62 * located by a path can be {@link #register registered} with a {@link
63 * WatchService} and entries in the directory watched. </p>
64 *
65 * <p> <b>WARNING:</b> This interface is only intended to be implemented by
66 * those developing custom file system implementations. Methods may be added to
67 * this interface in future releases. </p>
68 *
69 * <h2>Accessing Files</h2>
70 * <p> Paths may be used with the {@link Files} class to operate on files,
71 * directories, and other types of files. For example, suppose we want a {@link
72 * java.io.BufferedReader} to read text from a file "{@code access.log}". The
73 * file is located in a directory "{@code logs}" relative to the current working
74 * directory and is UTF-8 encoded.
75 * <pre>
76 * Path path = FileSystems.getDefault().getPath("logs", "access.log");
77 * BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8);
78 * </pre>
79 *
80 * <a id="interop"></a><h2>Interoperability</h2>
81 * <p> Paths associated with the default {@link
82 * java.nio.file.spi.FileSystemProvider provider} are generally interoperable
83 * with the {@link java.io.File java.io.File} class. Paths created by other
84 * providers are unlikely to be interoperable with the abstract path names
85 * represented by {@code java.io.File}. The {@link java.io.File#toPath toPath}
86 * method may be used to obtain a {@code Path} from the abstract path name
87 * represented by a {@code java.io.File} object. The resulting {@code Path} can
88 * be used to operate on the same file as the {@code java.io.File} object. In
89 * addition, the {@link #toFile toFile} method is useful to construct a {@code
90 * File} from the {@code String} representation of a {@code Path}.
91 *
92 * <h2>Concurrency</h2>
93 * <p> Implementations of this interface are immutable and safe for use by
94 * multiple concurrent threads.
95 *
96 * @since 1.7
97 */
98
99 public interface Path
100 extends Comparable<Path>, Iterable<Path>, Watchable
101 {
102 /**
103 * Converts a path string, or a sequence of strings that when joined form
104 * a path string, to a {@code Path}. If {@code more} does not specify any
105 * elements then the value of the {@code first} parameter is the path string
106 * to convert. If {@code more} specifies one or more elements then each
107 * non-empty string, including {@code first}, is considered to be a sequence
108 * of name elements and is joined to form a path string.
109 * The details as to how the Strings are joined is provider specific but
110 * typically they will be joined using the {@link FileSystem#getSeparator
111 * name-separator} as the separator. For example, if the name separator is
112 * "{@code /}" and {@code getPath("/foo","bar","gus")} is invoked, then the
113 * path string {@code "/foo/bar/gus"} is converted to a {@code Path}.
114 * A {@code Path} representing an empty path is returned if {@code first}
115 * is the empty string and {@code more} does not contain any non-empty
116 * strings.
117 *
118 * <p> The {@code Path} is obtained by invoking the {@link FileSystem#getPath
119 * getPath} method of the {@link FileSystems#getDefault default} {@link
120 * FileSystem}.
121 *
122 * <p> Note that while this method is very convenient, using it will imply
123 * an assumed reference to the default {@code FileSystem} and limit the
124 * utility of the calling code. Hence it should not be used in library code
125 * intended for flexible reuse. A more flexible alternative is to use an
126 * existing {@code Path} instance as an anchor, such as:
127 * <pre>
128 * Path dir = ...
129 * Path path = dir.resolve("file");
130 * </pre>
131 *
132 * @param first
133 * the path string or initial part of the path string
134 * @param more
135 * additional strings to be joined to form the path string
136 *
137 * @return the resulting {@code Path}
138 *
139 * @throws InvalidPathException
140 * if the path string cannot be converted to a {@code Path}
141 *
142 * @see FileSystem#getPath
143 */
144 public static Path get(String first, String... more) {
145 return FileSystems.getDefault().getPath(first, more);
146 }
147
148 /**
149 * Converts the given URI to a {@link Path} object.
150 *
151 * <p> This method iterates over the {@link FileSystemProvider#installedProviders()
152 * installed} providers to locate the provider that is identified by the
153 * URI {@link URI#getScheme scheme} of the given URI. URI schemes are
154 * compared without regard to case. If the provider is found then its {@link
155 * FileSystemProvider#getPath getPath} method is invoked to convert the
156 * URI.
157 *
158 * <p> In the case of the default provider, identified by the URI scheme
159 * "file", the given URI has a non-empty path component, and undefined query
160 * and fragment components. Whether the authority component may be present
161 * is platform specific. The returned {@code Path} is associated with the
162 * {@link FileSystems#getDefault default} file system.
163 *
164 * <p> The default provider provides a similar <em>round-trip</em> guarantee
165 * to the {@link java.io.File} class. For a given {@code Path} <i>p</i> it
166 * is guaranteed that
167 * <blockquote>{@code
168 * Path.get(}<i>p</i>{@code .}{@link Path#toUri() toUri}{@code ()).equals(}
169 * <i>p</i>{@code .}{@link Path#toAbsolutePath() toAbsolutePath}{@code ())}
170 * </blockquote>
171 * so long as the original {@code Path}, the {@code URI}, and the new {@code
172 * Path} are all created in (possibly different invocations of) the same
173 * Java virtual machine. Whether other providers make any guarantees is
174 * provider specific and therefore unspecified.
175 *
176 * @param uri
177 * the URI to convert
178 *
179 * @return the resulting {@code Path}
180 *
181 * @throws IllegalArgumentException
182 * if preconditions on the {@code uri} parameter do not hold. The
183 * format of the URI is provider specific.
184 * @throws FileSystemNotFoundException
185 * The file system, identified by the URI, does not exist and
186 * cannot be created automatically, or the provider identified by
187 * the URI's scheme component is not installed
188 * @throws SecurityException
189 * if a security manager is installed and it denies an unspecified
190 * permission to access the file system
191 */
192 public static Path get(URI uri) {
193 String scheme = uri.getScheme();
194 if (scheme == null)
195 throw new IllegalArgumentException("Missing scheme");
196
197 // check for default provider to avoid loading of installed providers
198 if (scheme.equalsIgnoreCase("file"))
199 return FileSystems.getDefault().provider().getPath(uri);
200
201 // try to find provider
202 for (FileSystemProvider provider: FileSystemProvider.installedProviders()) {
203 if (provider.getScheme().equalsIgnoreCase(scheme)) {
204 return provider.getPath(uri);
205 }
206 }
207
208 throw new FileSystemNotFoundException("Provider \"" + scheme + "\" not installed");
209 }
210
211 /**
212 * Returns the file system that created this object.
213 *
214 * @return the file system that created this object
215 */
216 FileSystem getFileSystem();
217
218 /**
219 * Tells whether or not this path is absolute.
220 *
221 * <p> An absolute path is complete in that it doesn't need to be combined
222 * with other path information in order to locate a file.
223 *
224 * @return {@code true} if, and only if, this path is absolute
225 */
226 boolean isAbsolute();
227
228 /**
229 * Returns the root component of this path as a {@code Path} object,
230 * or {@code null} if this path does not have a root component.
231 *
232 * @return a path representing the root component of this path,
233 * or {@code null}
234 */
235 Path getRoot();
236
237 /**
238 * Returns the name of the file or directory denoted by this path as a
239 * {@code Path} object. The file name is the <em>farthest</em> element from
240 * the root in the directory hierarchy.
241 *
242 * @return a path representing the name of the file or directory, or
243 * {@code null} if this path has zero elements
244 */
245 Path getFileName();
246
247 /**
248 * Returns the <em>parent path</em>, or {@code null} if this path does not
249 * have a parent.
250 *
251 * <p> The parent of this path object consists of this path's root
252 * component, if any, and each element in the path except for the
253 * <em>farthest</em> from the root in the directory hierarchy. This method
254 * does not access the file system; the path or its parent may not exist.
255 * Furthermore, this method does not eliminate special names such as "."
256 * and ".." that may be used in some implementations. On UNIX for example,
257 * the parent of "{@code /a/b/c}" is "{@code /a/b}", and the parent of
258 * {@code "x/y/.}" is "{@code x/y}". This method may be used with the {@link
259 * #normalize normalize} method, to eliminate redundant names, for cases where
260 * <em>shell-like</em> navigation is required.
261 *
262 * <p> If this path has more than one element, and no root component, then
263 * this method is equivalent to evaluating the expression:
264 * <blockquote><pre>
265 * subpath(0, getNameCount()-1);
266 * </pre></blockquote>
267 *
268 * @return a path representing the path's parent
269 */
270 Path getParent();
271
272 /**
273 * Returns the number of name elements in the path.
274 *
275 * @return the number of elements in the path, or {@code 0} if this path
276 * only represents a root component
277 */
278 int getNameCount();
279
280 /**
281 * Returns a name element of this path as a {@code Path} object.
282 *
283 * <p> The {@code index} parameter is the index of the name element to return.
284 * The element that is <em>closest</em> to the root in the directory hierarchy
285 * has index {@code 0}. The element that is <em>farthest</em> from the root
286 * has index {@link #getNameCount count}{@code -1}.
287 *
288 * @param index
289 * the index of the element
290 *
291 * @return the name element
292 *
293 * @throws IllegalArgumentException
294 * if {@code index} is negative, {@code index} is greater than or
295 * equal to the number of elements, or this path has zero name
296 * elements
297 */
298 Path getName(int index);
299
300 /**
301 * Returns a relative {@code Path} that is a subsequence of the name
302 * elements of this path.
303 *
304 * <p> The {@code beginIndex} and {@code endIndex} parameters specify the
305 * subsequence of name elements. The name that is <em>closest</em> to the root
306 * in the directory hierarchy has index {@code 0}. The name that is
307 * <em>farthest</em> from the root has index {@link #getNameCount
308 * count}{@code -1}. The returned {@code Path} object has the name elements
309 * that begin at {@code beginIndex} and extend to the element at index {@code
310 * endIndex-1}.
311 *
312 * @param beginIndex
313 * the index of the first element, inclusive
314 * @param endIndex
315 * the index of the last element, exclusive
316 *
317 * @return a new {@code Path} object that is a subsequence of the name
318 * elements in this {@code Path}
319 *
320 * @throws IllegalArgumentException
321 * if {@code beginIndex} is negative, or greater than or equal to
322 * the number of elements. If {@code endIndex} is less than or
323 * equal to {@code beginIndex}, or larger than the number of elements.
324 */
325 Path subpath(int beginIndex, int endIndex);
326
327 /**
328 * Tests if this path starts with the given path.
329 *
330 * <p> This path <em>starts</em> with the given path if this path's root
331 * component <em>starts</em> with the root component of the given path,
332 * and this path starts with the same name elements as the given path.
333 * If the given path has more name elements than this path then {@code false}
334 * is returned.
335 *
336 * <p> Whether or not the root component of this path starts with the root
337 * component of the given path is file system specific. If this path does
338 * not have a root component and the given path has a root component then
339 * this path does not start with the given path.
340 *
341 * <p> If the given path is associated with a different {@code FileSystem}
342 * to this path then {@code false} is returned.
343 *
344 * @param other
345 * the given path
346 *
347 * @return {@code true} if this path starts with the given path; otherwise
348 * {@code false}
349 */
350 boolean startsWith(Path other);
351
352 /**
353 * Tests if this path starts with a {@code Path}, constructed by converting
354 * the given path string, in exactly the manner specified by the {@link
355 * #startsWith(Path) startsWith(Path)} method. On UNIX for example, the path
356 * "{@code foo/bar}" starts with "{@code foo}" and "{@code foo/bar}". It
357 * does not start with "{@code f}" or "{@code fo}".
358 *
359 * @implSpec
360 * The default implementation is equivalent for this path to:
361 * <pre>{@code
362 * startsWith(getFileSystem().getPath(other));
363 * }</pre>
364 *
365 * @param other
366 * the given path string
367 *
368 * @return {@code true} if this path starts with the given path; otherwise
369 * {@code false}
370 *
371 * @throws InvalidPathException
372 * If the path string cannot be converted to a Path.
373 */
374 default boolean startsWith(String other) {
375 return startsWith(getFileSystem().getPath(other));
376 }
377
378 /**
379 * Tests if this path ends with the given path.
380 *
381 * <p> If the given path has <em>N</em> elements, and no root component,
382 * and this path has <em>N</em> or more elements, then this path ends with
383 * the given path if the last <em>N</em> elements of each path, starting at
384 * the element farthest from the root, are equal.
385 *
386 * <p> If the given path has a root component then this path ends with the
387 * given path if the root component of this path <em>ends with</em> the root
388 * component of the given path, and the corresponding elements of both paths
389 * are equal. Whether or not the root component of this path ends with the
390 * root component of the given path is file system specific. If this path
391 * does not have a root component and the given path has a root component
392 * then this path does not end with the given path.
393 *
394 * <p> If the given path is associated with a different {@code FileSystem}
395 * to this path then {@code false} is returned.
396 *
397 * @param other
398 * the given path
399 *
400 * @return {@code true} if this path ends with the given path; otherwise
401 * {@code false}
402 */
403 boolean endsWith(Path other);
404
405 /**
406 * Tests if this path ends with a {@code Path}, constructed by converting
407 * the given path string, in exactly the manner specified by the {@link
408 * #endsWith(Path) endsWith(Path)} method. On UNIX for example, the path
409 * "{@code foo/bar}" ends with "{@code foo/bar}" and "{@code bar}". It does
410 * not end with "{@code r}" or "{@code /bar}". Note that trailing separators
411 * are not taken into account, and so invoking this method on the {@code
412 * Path}"{@code foo/bar}" with the {@code String} "{@code bar/}" returns
413 * {@code true}.
414 *
415 * @implSpec
416 * The default implementation is equivalent for this path to:
417 * <pre>{@code
418 * endsWith(getFileSystem().getPath(other));
419 * }</pre>
420 *
421 * @param other
422 * the given path string
423 *
424 * @return {@code true} if this path ends with the given path; otherwise
425 * {@code false}
426 *
427 * @throws InvalidPathException
428 * If the path string cannot be converted to a Path.
429 */
430 default boolean endsWith(String other) {
431 return endsWith(getFileSystem().getPath(other));
432 }
433
434 /**
435 * Returns a path that is this path with redundant name elements eliminated.
436 *
437 * <p> The precise definition of this method is implementation dependent but
438 * in general it derives from this path, a path that does not contain
439 * <em>redundant</em> name elements. In many file systems, the "{@code .}"
440 * and "{@code ..}" are special names used to indicate the current directory
441 * and parent directory. In such file systems all occurrences of "{@code .}"
442 * are considered redundant. If a "{@code ..}" is preceded by a
443 * non-"{@code ..}" name then both names are considered redundant (the
444 * process to identify such names is repeated until it is no longer
445 * applicable).
446 *
447 * <p> This method does not access the file system; the path may not locate
448 * a file that exists. Eliminating "{@code ..}" and a preceding name from a
449 * path may result in the path that locates a different file than the original
450 * path. This can arise when the preceding name is a symbolic link.
451 *
452 * @return the resulting path or this path if it does not contain
453 * redundant name elements; an empty path is returned if this path
454 * does not have a root component and all name elements are redundant
455 *
456 * @see #getParent
457 * @see #toRealPath
458 */
459 Path normalize();
460
461 // -- resolution and relativization --
462
463 /**
464 * Resolve the given path against this path.
465 *
466 * <p> If the {@code other} parameter is an {@link #isAbsolute() absolute}
467 * path then this method trivially returns {@code other}. If {@code other}
468 * is an <i>empty path</i> then this method trivially returns this path.
469 * Otherwise this method considers this path to be a directory and resolves
470 * the given path against this path. In the simplest case, the given path
471 * does not have a {@link #getRoot root} component, in which case this method
472 * <em>joins</em> the given path to this path and returns a resulting path
473 * that {@link #endsWith ends} with the given path. Where the given path has
474 * a root component then resolution is highly implementation dependent and
475 * therefore unspecified.
476 *
477 * @param other
478 * the path to resolve against this path
479 *
480 * @return the resulting path
481 *
482 * @see #relativize
483 */
484 Path resolve(Path other);
485
486 /**
487 * Converts a given path string to a {@code Path} and resolves it against
488 * this {@code Path} in exactly the manner specified by the {@link
489 * #resolve(Path) resolve} method. For example, suppose that the name
490 * separator is "{@code /}" and a path represents "{@code foo/bar}", then
491 * invoking this method with the path string "{@code gus}" will result in
492 * the {@code Path} "{@code foo/bar/gus}".
493 *
494 * @implSpec
495 * The default implementation is equivalent for this path to:
496 * <pre>{@code
497 * resolve(getFileSystem().getPath(other));
498 * }</pre>
499 *
500 * @param other
501 * the path string to resolve against this path
502 *
503 * @return the resulting path
504 *
505 * @throws InvalidPathException
506 * if the path string cannot be converted to a Path.
507 *
508 * @see FileSystem#getPath
509 */
510 default Path resolve(String other) {
511 return resolve(getFileSystem().getPath(other));
512 }
513
514 /**
515 * Resolves the given path against this path's {@link #getParent parent}
516 * path. This is useful where a file name needs to be <i>replaced</i> with
517 * another file name. For example, suppose that the name separator is
518 * "{@code /}" and a path represents "{@code dir1/dir2/foo}", then invoking
519 * this method with the {@code Path} "{@code bar}" will result in the {@code
520 * Path} "{@code dir1/dir2/bar}". If this path does not have a parent path,
521 * or {@code other} is {@link #isAbsolute() absolute}, then this method
522 * returns {@code other}. If {@code other} is an empty path then this method
523 * returns this path's parent, or where this path doesn't have a parent, the
524 * empty path.
525 *
526 * @implSpec
527 * The default implementation is equivalent for this path to:
528 * <pre>{@code
529 * (getParent() == null) ? other : getParent().resolve(other);
530 * }</pre>
531 * unless {@code other == null}, in which case a
532 * {@code NullPointerException} is thrown.
533 *
534 * @param other
535 * the path to resolve against this path's parent
536 *
537 * @return the resulting path
538 *
539 * @see #resolve(Path)
540 */
541 default Path resolveSibling(Path other) {
542 if (other == null)
543 throw new NullPointerException();
544 Path parent = getParent();
545 return (parent == null) ? other : parent.resolve(other);
546 }
547
548 /**
549 * Converts a given path string to a {@code Path} and resolves it against
550 * this path's {@link #getParent parent} path in exactly the manner
551 * specified by the {@link #resolveSibling(Path) resolveSibling} method.
552 *
553 * @implSpec
554 * The default implementation is equivalent for this path to:
555 * <pre>{@code
556 * resolveSibling(getFileSystem().getPath(other));
557 * }</pre>
558 *
559 * @param other
560 * the path string to resolve against this path's parent
561 *
562 * @return the resulting path
563 *
564 * @throws InvalidPathException
565 * if the path string cannot be converted to a Path.
566 *
567 * @see FileSystem#getPath
568 */
569 default Path resolveSibling(String other) {
570 return resolveSibling(getFileSystem().getPath(other));
571 }
572
573 /**
574 * Constructs a relative path between this path and a given path.
575 *
576 * <p> Relativization is the inverse of {@link #resolve(Path) resolution}.
577 * This method attempts to construct a {@link #isAbsolute relative} path
578 * that when {@link #resolve(Path) resolved} against this path, yields a
579 * path that locates the same file as the given path. For example, on UNIX,
580 * if this path is {@code "/a/b"} and the given path is {@code "/a/b/c/d"}
581 * then the resulting relative path would be {@code "c/d"}. Where this
582 * path and the given path do not have a {@link #getRoot root} component,
583 * then a relative path can be constructed. A relative path cannot be
584 * constructed if only one of the paths have a root component. Where both
585 * paths have a root component then it is implementation dependent if a
586 * relative path can be constructed. If this path and the given path are
587 * {@link #equals equal} then an <i>empty path</i> is returned.
588 *
589 * <p> For any two {@link #normalize normalized} paths <i>p</i> and
590 * <i>q</i>, where <i>q</i> does not have a root component,
591 * <blockquote>
592 * <i>p</i>{@code .relativize(}<i>p</i>
593 * {@code .resolve(}<i>q</i>{@code )).equals(}<i>q</i>{@code )}
594 * </blockquote>
595 *
596 * <p> When symbolic links are supported, then whether the resulting path,
597 * when resolved against this path, yields a path that can be used to locate
598 * the {@link Files#isSameFile same} file as {@code other} is implementation
599 * dependent. For example, if this path is {@code "/a/b"} and the given
600 * path is {@code "/a/x"} then the resulting relative path may be {@code
601 * "../x"}. If {@code "b"} is a symbolic link then is implementation
602 * dependent if {@code "a/b/../x"} would locate the same file as {@code "/a/x"}.
603 *
604 * @param other
605 * the path to relativize against this path
606 *
607 * @return the resulting relative path, or an empty path if both paths are
608 * equal
609 *
610 * @throws IllegalArgumentException
611 * if {@code other} is not a {@code Path} that can be relativized
612 * against this path
613 */
614 Path relativize(Path other);
615
616 /**
617 * Returns a URI to represent this path.
618 *
619 * <p> This method constructs an absolute {@link URI} with a {@link
620 * URI#getScheme() scheme} equal to the URI scheme that identifies the
621 * provider. The exact form of the scheme specific part is highly provider
622 * dependent.
623 *
624 * <p> In the case of the default provider, the URI is hierarchical with
625 * a {@link URI#getPath() path} component that is absolute. The query and
626 * fragment components are undefined. Whether the authority component is
627 * defined or not is implementation dependent. There is no guarantee that
628 * the {@code URI} may be used to construct a {@link java.io.File java.io.File}.
629 * In particular, if this path represents a Universal Naming Convention (UNC)
630 * path, then the UNC server name may be encoded in the authority component
631 * of the resulting URI. In the case of the default provider, and the file
632 * exists, and it can be determined that the file is a directory, then the
633 * resulting {@code URI} will end with a slash.
634 *
635 * <p> The default provider provides a similar <em>round-trip</em> guarantee
636 * to the {@link java.io.File} class. For a given {@code Path} <i>p</i> it
637 * is guaranteed that
638 * <blockquote>
639 * {@link Path#get(URI) Path.get}{@code (}<i>p</i>{@code .toUri()).equals(}<i>p</i>
640 * {@code .}{@link #toAbsolutePath() toAbsolutePath}{@code ())}
641 * </blockquote>
642 * so long as the original {@code Path}, the {@code URI}, and the new {@code
643 * Path} are all created in (possibly different invocations of) the same
644 * Java virtual machine. Whether other providers make any guarantees is
645 * provider specific and therefore unspecified.
646 *
647 * <p> When a file system is constructed to access the contents of a file
648 * as a file system then it is highly implementation specific if the returned
649 * URI represents the given path in the file system or it represents a
650 * <em>compound</em> URI that encodes the URI of the enclosing file system.
651 * A format for compound URIs is not defined in this release; such a scheme
652 * may be added in a future release.
653 *
654 * @return the URI representing this path
655 *
656 * @throws java.io.IOError
657 * if an I/O error occurs obtaining the absolute path, or where a
658 * file system is constructed to access the contents of a file as
659 * a file system, and the URI of the enclosing file system cannot be
660 * obtained
661 *
662 * @throws SecurityException
663 * In the case of the default provider, and a security manager
664 * is installed, the {@link #toAbsolutePath toAbsolutePath} method
665 * throws a security exception.
666 */
667 URI toUri();
668
669 /**
670 * Returns a {@code Path} object representing the absolute path of this
671 * path.
672 *
673 * <p> If this path is already {@link Path#isAbsolute absolute} then this
674 * method simply returns this path. Otherwise, this method resolves the path
675 * in an implementation dependent manner, typically by resolving the path
676 * against a file system default directory. Depending on the implementation,
677 * this method may throw an I/O error if the file system is not accessible.
678 *
679 * @return a {@code Path} object representing the absolute path
680 *
681 * @throws java.io.IOError
682 * if an I/O error occurs
683 * @throws SecurityException
684 * In the case of the default provider, a security manager
685 * is installed, and this path is not absolute, then the security
686 * manager's {@link SecurityManager#checkPropertyAccess(String)
687 * checkPropertyAccess} method is invoked to check access to the
688 * system property {@code user.dir}
689 */
690 Path toAbsolutePath();
691
692 /**
693 * Returns the <em>real</em> path of an existing file.
694 *
695 * <p> The precise definition of this method is implementation dependent but
696 * in general it derives from this path, an {@link #isAbsolute absolute}
697 * path that locates the {@link Files#isSameFile same} file as this path, but
698 * with name elements that represent the actual name of the directories
699 * and the file. For example, where filename comparisons on a file system
700 * are case insensitive then the name elements represent the names in their
701 * actual case. Additionally, the resulting path has redundant name
702 * elements removed.
703 *
704 * <p> If this path is relative then its absolute path is first obtained,
705 * as if by invoking the {@link #toAbsolutePath toAbsolutePath} method.
706 *
707 * <p> The {@code options} array may be used to indicate how symbolic links
708 * are handled. By default, symbolic links are resolved to their final
709 * target. If the option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is
710 * present then this method does not resolve symbolic links.
711 *
712 * Some implementations allow special names such as "{@code ..}" to refer to
713 * the parent directory. When deriving the <em>real path</em>, and a
714 * "{@code ..}" (or equivalent) is preceded by a non-"{@code ..}" name then
715 * an implementation will typically cause both names to be removed. When
716 * not resolving symbolic links and the preceding name is a symbolic link
717 * then the names are only removed if it guaranteed that the resulting path
718 * will locate the same file as this path.
719 *
720 * @param options
721 * options indicating how symbolic links are handled
722 *
723 * @return an absolute path represent the <em>real</em> path of the file
724 * located by this object
725 *
726 * @throws IOException
727 * if the file does not exist or an I/O error occurs
728 * @throws SecurityException
729 * In the case of the default provider, and a security manager
730 * is installed, its {@link SecurityManager#checkRead(String) checkRead}
731 * method is invoked to check read access to the file, and where
732 * this path is not absolute, its {@link SecurityManager#checkPropertyAccess(String)
733 * checkPropertyAccess} method is invoked to check access to the
734 * system property {@code user.dir}
735 */
736 Path toRealPath(LinkOption... options) throws IOException;
737
738 /**
739 * Returns a {@link File} object representing this path. Where this {@code
740 * Path} is associated with the default provider, then this method is
741 * equivalent to returning a {@code File} object constructed with the
742 * {@code String} representation of this path.
743 *
744 * <p> If this path was created by invoking the {@code File} {@link
745 * File#toPath toPath} method then there is no guarantee that the {@code
746 * File} object returned by this method is {@link #equals equal} to the
747 * original {@code File}.
748 *
749 * @implSpec
750 * The default implementation is equivalent for this path to:
751 * <pre>{@code
752 * new File(toString());
753 * }</pre>
754 * if the {@code FileSystem} which created this {@code Path} is the default
755 * file system; otherwise an {@code UnsupportedOperationException} is
756 * thrown.
757 *
758 * @return a {@code File} object representing this path
759 *
760 * @throws UnsupportedOperationException
761 * if this {@code Path} is not associated with the default provider
762 */
763 default File toFile() {
764 if (getFileSystem() == FileSystems.getDefault()) {
765 return new File(toString());
766 } else {
767 throw new UnsupportedOperationException("Path not associated with "
768 + "default file system.");
769 }
770 }
771
772 // -- watchable --
773
774 /**
775 * Registers the file located by this path with a watch service.
776 *
777 * <p> In this release, this path locates a directory that exists. The
778 * directory is registered with the watch service so that entries in the
779 * directory can be watched. The {@code events} parameter is the events to
780 * register and may contain the following events:
781 * <ul>
782 * <li>{@link StandardWatchEventKinds#ENTRY_CREATE ENTRY_CREATE} -
783 * entry created or moved into the directory</li>
784 * <li>{@link StandardWatchEventKinds#ENTRY_DELETE ENTRY_DELETE} -
785 * entry deleted or moved out of the directory</li>
786 * <li>{@link StandardWatchEventKinds#ENTRY_MODIFY ENTRY_MODIFY} -
787 * entry in directory was modified</li>
788 * </ul>
789 *
790 * <p> The {@link WatchEvent#context context} for these events is the
791 * relative path between the directory located by this path, and the path
792 * that locates the directory entry that is created, deleted, or modified.
793 *
794 * <p> The set of events may include additional implementation specific
795 * event that are not defined by the enum {@link StandardWatchEventKinds}
796 *
797 * <p> The {@code modifiers} parameter specifies <em>modifiers</em> that
798 * qualify how the directory is registered. This release does not define any
799 * <em>standard</em> modifiers. It may contain implementation specific
800 * modifiers.
801 *
802 * <p> Where a file is registered with a watch service by means of a symbolic
803 * link then it is implementation specific if the watch continues to depend
804 * on the existence of the symbolic link after it is registered.
805 *
806 * @param watcher
807 * the watch service to which this object is to be registered
808 * @param events
809 * the events for which this object should be registered
810 * @param modifiers
811 * the modifiers, if any, that modify how the object is registered
812 *
813 * @return a key representing the registration of this object with the
814 * given watch service
815 *
816 * @throws UnsupportedOperationException
817 * if unsupported events or modifiers are specified
818 * @throws IllegalArgumentException
819 * if an invalid combination of events or modifiers is specified
820 * @throws ClosedWatchServiceException
821 * if the watch service is closed
822 * @throws NotDirectoryException
823 * if the file is registered to watch the entries in a directory
824 * and the file is not a directory <i>(optional specific exception)</i>
825 * @throws IOException
826 * if an I/O error occurs
827 * @throws SecurityException
828 * In the case of the default provider, and a security manager is
829 * installed, the {@link SecurityManager#checkRead(String) checkRead}
830 * method is invoked to check read access to the file.
831 */
832 @Override
833 WatchKey register(WatchService watcher,
834 WatchEvent.Kind<?>[] events,
835 WatchEvent.Modifier... modifiers)
836 throws IOException;
837
838 /**
839 * Registers the file located by this path with a watch service.
840 *
841 * <p> An invocation of this method behaves in exactly the same way as the
842 * invocation
843 * <pre>
844 * watchable.{@link #register(WatchService,WatchEvent.Kind[],WatchEvent.Modifier[]) register}(watcher, events, new WatchEvent.Modifier[0]);
845 * </pre>
846 *
847 * <p> <b>Usage Example:</b>
848 * Suppose we wish to register a directory for entry create, delete, and modify
849 * events:
850 * <pre>
851 * Path dir = ...
852 * WatchService watcher = ...
853 *
854 * WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
855 * </pre>
856 *
857 * @implSpec
858 * The default implementation is equivalent for this path to:
859 * <pre>{@code
860 * register(watcher, events, new WatchEvent.Modifier[0]);
861 * }</pre>
862 *
863 * @param watcher
864 * The watch service to which this object is to be registered
865 * @param events
866 * The events for which this object should be registered
867 *
868 * @return A key representing the registration of this object with the
869 * given watch service
870 *
871 * @throws UnsupportedOperationException
872 * If unsupported events are specified
873 * @throws IllegalArgumentException
874 * If an invalid combination of events is specified
875 * @throws ClosedWatchServiceException
876 * If the watch service is closed
877 * @throws NotDirectoryException
878 * If the file is registered to watch the entries in a directory
879 * and the file is not a directory <i>(optional specific exception)</i>
880 * @throws IOException
881 * If an I/O error occurs
882 * @throws SecurityException
883 * In the case of the default provider, and a security manager is
884 * installed, the {@link SecurityManager#checkRead(String) checkRead}
885 * method is invoked to check read access to the file.
886 */
887 @Override
888 default WatchKey register(WatchService watcher,
889 WatchEvent.Kind<?>... events) throws IOException {
890 return register(watcher, events, new WatchEvent.Modifier[0]);
891 }
892
893 // -- Iterable --
894
895 /**
896 * Returns an iterator over the name elements of this path.
897 *
898 * <p> The first element returned by the iterator represents the name
899 * element that is closest to the root in the directory hierarchy, the
900 * second element is the next closest, and so on. The last element returned
901 * is the name of the file or directory denoted by this path. The {@link
902 * #getRoot root} component, if present, is not returned by the iterator.
903 *
904 * @implSpec
905 * The default implementation returns an {@code Iterator<Path>} which, for
906 * this path, traverses the {@code Path}s returned by
907 * {@code getName(index)}, where {@code index} ranges from zero to
908 * {@code getNameCount() - 1}, inclusive.
909 *
910 * @return an iterator over the name elements of this path.
911 */
912 @Override
913 default Iterator<Path> iterator() {
914 return new Iterator<>() {
915 private int i = 0;
916
917 @Override
918 public boolean hasNext() {
919 return (i < getNameCount());
920 }
921
922 @Override
923 public Path next() {
924 if (i < getNameCount()) {
925 Path result = getName(i);
926 i++;
927 return result;
928 } else {
929 throw new NoSuchElementException();
930 }
931 }
932 };
933 }
934
935 // -- compareTo/equals/hashCode --
936
937 /**
938 * Compares two abstract paths lexicographically. The ordering defined by
939 * this method is provider specific, and in the case of the default
940 * provider, platform specific. This method does not access the file system
941 * and neither file is required to exist.
942 *
943 * <p> This method may not be used to compare paths that are associated
944 * with different file system providers.
945 *
946 * @param other the path compared to this path.
947 *
948 * @return zero if the argument is {@link #equals equal} to this path, a
949 * value less than zero if this path is lexicographically less than
950 * the argument, or a value greater than zero if this path is
951 * lexicographically greater than the argument
952 *
953 * @throws ClassCastException
954 * if the paths are associated with different providers
955 */
956 @Override
957 int compareTo(Path other);
958
959 /**
960 * Tests this path for equality with the given object.
961 *
962 * <p> If the given object is not a Path, or is a Path associated with a
963 * different {@code FileSystem}, then this method returns {@code false}.
964 *
965 * <p> Whether or not two path are equal depends on the file system
966 * implementation. In some cases the paths are compared without regard
967 * to case, and others are case sensitive. This method does not access the
968 * file system and the file is not required to exist. Where required, the
969 * {@link Files#isSameFile isSameFile} method may be used to check if two
970 * paths locate the same file.
971 *
972 * <p> This method satisfies the general contract of the {@link
973 * java.lang.Object#equals(Object) Object.equals} method. </p>
974 *
975 * @param other
976 * the object to which this object is to be compared
977 *
978 * @return {@code true} if, and only if, the given object is a {@code Path}
979 * that is identical to this {@code Path}
980 */
981 boolean equals(Object other);
982
983 /**
984 * Computes a hash code for this path.
985 *
986 * <p> The hash code is based upon the components of the path, and
987 * satisfies the general contract of the {@link Object#hashCode
988 * Object.hashCode} method.
989 *
990 * @return the hash-code value for this path
991 */
992 int hashCode();
993
994 /**
995 * Returns the string representation of this path.
996 *
997 * <p> If this path was created by converting a path string using the
998 * {@link FileSystem#getPath getPath} method then the path string returned
999 * by this method may differ from the original String used to create the path.
1000 *
1001 * <p> The returned path string uses the default name {@link
1002 * FileSystem#getSeparator separator} to separate names in the path.
1003 *
1004 * @return the string representation of this path
1005 */
1006 String toString();
1007 }