View Javadoc
1   /*
2    * Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
6    * under the terms of the GNU General Public License version 2 only, as
7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
18   * 2 along with this work; if not, write to the Free Software Foundation,
19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
21   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22   * or visit www.oracle.com if you need additional information or have any
23   * questions.
24   */
25  
26  package java.nio.file;
27  
28  import java.io.File;
29  import java.io.IOException;
30  import java.net.URI;
31  import java.util.Iterator;
32  
33  /**
34   * An object that may be used to locate a file in a file system. It will
35   * typically represent a system dependent file path.
36   *
37   * <p> A {@code Path} represents a path that is hierarchical and composed of a
38   * sequence of directory and file name elements separated by a special separator
39   * or delimiter. A <em>root component</em>, that identifies a file system
40   * hierarchy, may also be present. The name element that is <em>farthest</em>
41   * from the root of the directory hierarchy is the name of a file or directory.
42   * The other name elements are directory names. A {@code Path} can represent a
43   * root, a root and a sequence of names, or simply one or more name elements.
44   * A {@code Path} is considered to be an <i>empty path</i> if it consists
45   * solely of one name element that is empty. Accessing a file using an
46   * <i>empty path</i> is equivalent to accessing the default directory of the
47   * file system. {@code Path} defines the {@link #getFileName() getFileName},
48   * {@link #getParent getParent}, {@link #getRoot getRoot}, and {@link #subpath
49   * subpath} methods to access the path components or a subsequence of its name
50   * elements.
51   *
52   * <p> In addition to accessing the components of a path, a {@code Path} also
53   * defines the {@link #resolve(Path) resolve} and {@link #resolveSibling(Path)
54   * resolveSibling} methods to combine paths. The {@link #relativize relativize}
55   * method that can be used to construct a relative path between two paths.
56   * Paths can be {@link #compareTo compared}, and tested against each other using
57   * the {@link #startsWith startsWith} and {@link #endsWith endsWith} methods.
58   *
59   * <p> This interface extends {@link Watchable} interface so that a directory
60   * located by a path can be {@link #register registered} with a {@link
61   * WatchService} and entries in the directory watched. </p>
62   *
63   * <p> <b>WARNING:</b> This interface is only intended to be implemented by
64   * those developing custom file system implementations. Methods may be added to
65   * this interface in future releases. </p>
66   *
67   * <h2>Accessing Files</h2>
68   * <p> Paths may be used with the {@link Files} class to operate on files,
69   * directories, and other types of files. For example, suppose we want a {@link
70   * java.io.BufferedReader} to read text from a file "{@code access.log}". The
71   * file is located in a directory "{@code logs}" relative to the current working
72   * directory and is UTF-8 encoded.
73   * <pre>
74   *     Path path = FileSystems.getDefault().getPath("logs", "access.log");
75   *     BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8);
76   * </pre>
77   *
78   * <a name="interop"></a><h2>Interoperability</h2>
79   * <p> Paths associated with the default {@link
80   * java.nio.file.spi.FileSystemProvider provider} are generally interoperable
81   * with the {@link java.io.File java.io.File} class. Paths created by other
82   * providers are unlikely to be interoperable with the abstract path names
83   * represented by {@code java.io.File}. The {@link java.io.File#toPath toPath}
84   * method may be used to obtain a {@code Path} from the abstract path name
85   * represented by a {@code java.io.File} object. The resulting {@code Path} can
86   * be used to operate on the same file as the {@code java.io.File} object. In
87   * addition, the {@link #toFile toFile} method is useful to construct a {@code
88   * File} from the {@code String} representation of a {@code Path}.
89   *
90   * <h2>Concurrency</h2>
91   * <p> Implementations of this interface are immutable and safe for use by
92   * multiple concurrent threads.
93   *
94   * @since 1.7
95   * @see Paths
96   */
97  
98  public interface Path
99      extends Comparable<Path>, Iterable<Path>, Watchable
100 {
101     /**
102      * Returns the file system that created this object.
103      *
104      * @return  the file system that created this object
105      */
106     FileSystem getFileSystem();
107 
108     /**
109      * Tells whether or not this path is absolute.
110      *
111      * <p> An absolute path is complete in that it doesn't need to be combined
112      * with other path information in order to locate a file.
113      *
114      * @return  {@code true} if, and only if, this path is absolute
115      */
116     boolean isAbsolute();
117 
118     /**
119      * Returns the root component of this path as a {@code Path} object,
120      * or {@code null} if this path does not have a root component.
121      *
122      * @return  a path representing the root component of this path,
123      *          or {@code null}
124      */
125     Path getRoot();
126 
127     /**
128      * Returns the name of the file or directory denoted by this path as a
129      * {@code Path} object. The file name is the <em>farthest</em> element from
130      * the root in the directory hierarchy.
131      *
132      * @return  a path representing the name of the file or directory, or
133      *          {@code null} if this path has zero elements
134      */
135     Path getFileName();
136 
137     /**
138      * Returns the <em>parent path</em>, or {@code null} if this path does not
139      * have a parent.
140      *
141      * <p> The parent of this path object consists of this path's root
142      * component, if any, and each element in the path except for the
143      * <em>farthest</em> from the root in the directory hierarchy. This method
144      * does not access the file system; the path or its parent may not exist.
145      * Furthermore, this method does not eliminate special names such as "."
146      * and ".." that may be used in some implementations. On UNIX for example,
147      * the parent of "{@code /a/b/c}" is "{@code /a/b}", and the parent of
148      * {@code "x/y/.}" is "{@code x/y}". This method may be used with the {@link
149      * #normalize normalize} method, to eliminate redundant names, for cases where
150      * <em>shell-like</em> navigation is required.
151      *
152      * <p> If this path has one or more elements, and no root component, then
153      * this method is equivalent to evaluating the expression:
154      * <blockquote><pre>
155      * subpath(0,&nbsp;getNameCount()-1);
156      * </pre></blockquote>
157      *
158      * @return  a path representing the path's parent
159      */
160     Path getParent();
161 
162     /**
163      * Returns the number of name elements in the path.
164      *
165      * @return  the number of elements in the path, or {@code 0} if this path
166      *          only represents a root component
167      */
168     int getNameCount();
169 
170     /**
171      * Returns a name element of this path as a {@code Path} object.
172      *
173      * <p> The {@code index} parameter is the index of the name element to return.
174      * The element that is <em>closest</em> to the root in the directory hierarchy
175      * has index {@code 0}. The element that is <em>farthest</em> from the root
176      * has index {@link #getNameCount count}{@code -1}.
177      *
178      * @param   index
179      *          the index of the element
180      *
181      * @return  the name element
182      *
183      * @throws  IllegalArgumentException
184      *          if {@code index} is negative, {@code index} is greater than or
185      *          equal to the number of elements, or this path has zero name
186      *          elements
187      */
188     Path getName(int index);
189 
190     /**
191      * Returns a relative {@code Path} that is a subsequence of the name
192      * elements of this path.
193      *
194      * <p> The {@code beginIndex} and {@code endIndex} parameters specify the
195      * subsequence of name elements. The name that is <em>closest</em> to the root
196      * in the directory hierarchy has index {@code 0}. The name that is
197      * <em>farthest</em> from the root has index {@link #getNameCount
198      * count}{@code -1}. The returned {@code Path} object has the name elements
199      * that begin at {@code beginIndex} and extend to the element at index {@code
200      * endIndex-1}.
201      *
202      * @param   beginIndex
203      *          the index of the first element, inclusive
204      * @param   endIndex
205      *          the index of the last element, exclusive
206      *
207      * @return  a new {@code Path} object that is a subsequence of the name
208      *          elements in this {@code Path}
209      *
210      * @throws  IllegalArgumentException
211      *          if {@code beginIndex} is negative, or greater than or equal to
212      *          the number of elements. If {@code endIndex} is less than or
213      *          equal to {@code beginIndex}, or larger than the number of elements.
214      */
215     Path subpath(int beginIndex, int endIndex);
216 
217     /**
218      * Tests if this path starts with the given path.
219      *
220      * <p> This path <em>starts</em> with the given path if this path's root
221      * component <em>starts</em> with the root component of the given path,
222      * and this path starts with the same name elements as the given path.
223      * If the given path has more name elements than this path then {@code false}
224      * is returned.
225      *
226      * <p> Whether or not the root component of this path starts with the root
227      * component of the given path is file system specific. If this path does
228      * not have a root component and the given path has a root component then
229      * this path does not start with the given path.
230      *
231      * <p> If the given path is associated with a different {@code FileSystem}
232      * to this path then {@code false} is returned.
233      *
234      * @param   other
235      *          the given path
236      *
237      * @return  {@code true} if this path starts with the given path; otherwise
238      *          {@code false}
239      */
240     boolean startsWith(Path other);
241 
242     /**
243      * Tests if this path starts with a {@code Path}, constructed by converting
244      * the given path string, in exactly the manner specified by the {@link
245      * #startsWith(Path) startsWith(Path)} method. On UNIX for example, the path
246      * "{@code foo/bar}" starts with "{@code foo}" and "{@code foo/bar}". It
247      * does not start with "{@code f}" or "{@code fo}".
248      *
249      * @param   other
250      *          the given path string
251      *
252      * @return  {@code true} if this path starts with the given path; otherwise
253      *          {@code false}
254      *
255      * @throws  InvalidPathException
256      *          If the path string cannot be converted to a Path.
257      */
258     boolean startsWith(String other);
259 
260     /**
261      * Tests if this path ends with the given path.
262      *
263      * <p> If the given path has <em>N</em> elements, and no root component,
264      * and this path has <em>N</em> or more elements, then this path ends with
265      * the given path if the last <em>N</em> elements of each path, starting at
266      * the element farthest from the root, are equal.
267      *
268      * <p> If the given path has a root component then this path ends with the
269      * given path if the root component of this path <em>ends with</em> the root
270      * component of the given path, and the corresponding elements of both paths
271      * are equal. Whether or not the root component of this path ends with the
272      * root component of the given path is file system specific. If this path
273      * does not have a root component and the given path has a root component
274      * then this path does not end with the given path.
275      *
276      * <p> If the given path is associated with a different {@code FileSystem}
277      * to this path then {@code false} is returned.
278      *
279      * @param   other
280      *          the given path
281      *
282      * @return  {@code true} if this path ends with the given path; otherwise
283      *          {@code false}
284      */
285     boolean endsWith(Path other);
286 
287     /**
288      * Tests if this path ends with a {@code Path}, constructed by converting
289      * the given path string, in exactly the manner specified by the {@link
290      * #endsWith(Path) endsWith(Path)} method. On UNIX for example, the path
291      * "{@code foo/bar}" ends with "{@code foo/bar}" and "{@code bar}". It does
292      * not end with "{@code r}" or "{@code /bar}". Note that trailing separators
293      * are not taken into account, and so invoking this method on the {@code
294      * Path}"{@code foo/bar}" with the {@code String} "{@code bar/}" returns
295      * {@code true}.
296      *
297      * @param   other
298      *          the given path string
299      *
300      * @return  {@code true} if this path ends with the given path; otherwise
301      *          {@code false}
302      *
303      * @throws  InvalidPathException
304      *          If the path string cannot be converted to a Path.
305      */
306     boolean endsWith(String other);
307 
308     /**
309      * Returns a path that is this path with redundant name elements eliminated.
310      *
311      * <p> The precise definition of this method is implementation dependent but
312      * in general it derives from this path, a path that does not contain
313      * <em>redundant</em> name elements. In many file systems, the "{@code .}"
314      * and "{@code ..}" are special names used to indicate the current directory
315      * and parent directory. In such file systems all occurrences of "{@code .}"
316      * are considered redundant. If a "{@code ..}" is preceded by a
317      * non-"{@code ..}" name then both names are considered redundant (the
318      * process to identify such names is repeated until it is no longer
319      * applicable).
320      *
321      * <p> This method does not access the file system; the path may not locate
322      * a file that exists. Eliminating "{@code ..}" and a preceding name from a
323      * path may result in the path that locates a different file than the original
324      * path. This can arise when the preceding name is a symbolic link.
325      *
326      * @return  the resulting path or this path if it does not contain
327      *          redundant name elements; an empty path is returned if this path
328      *          does have a root component and all name elements are redundant
329      *
330      * @see #getParent
331      * @see #toRealPath
332      */
333     Path normalize();
334 
335     // -- resolution and relativization --
336 
337     /**
338      * Resolve the given path against this path.
339      *
340      * <p> If the {@code other} parameter is an {@link #isAbsolute() absolute}
341      * path then this method trivially returns {@code other}. If {@code other}
342      * is an <i>empty path</i> then this method trivially returns this path.
343      * Otherwise this method considers this path to be a directory and resolves
344      * the given path against this path. In the simplest case, the given path
345      * does not have a {@link #getRoot root} component, in which case this method
346      * <em>joins</em> the given path to this path and returns a resulting path
347      * that {@link #endsWith ends} with the given path. Where the given path has
348      * a root component then resolution is highly implementation dependent and
349      * therefore unspecified.
350      *
351      * @param   other
352      *          the path to resolve against this path
353      *
354      * @return  the resulting path
355      *
356      * @see #relativize
357      */
358     Path resolve(Path other);
359 
360     /**
361      * Converts a given path string to a {@code Path} and resolves it against
362      * this {@code Path} in exactly the manner specified by the {@link
363      * #resolve(Path) resolve} method. For example, suppose that the name
364      * separator is "{@code /}" and a path represents "{@code foo/bar}", then
365      * invoking this method with the path string "{@code gus}" will result in
366      * the {@code Path} "{@code foo/bar/gus}".
367      *
368      * @param   other
369      *          the path string to resolve against this path
370      *
371      * @return  the resulting path
372      *
373      * @throws  InvalidPathException
374      *          if the path string cannot be converted to a Path.
375      *
376      * @see FileSystem#getPath
377      */
378     Path resolve(String other);
379 
380     /**
381      * Resolves the given path against this path's {@link #getParent parent}
382      * path. This is useful where a file name needs to be <i>replaced</i> with
383      * another file name. For example, suppose that the name separator is
384      * "{@code /}" and a path represents "{@code dir1/dir2/foo}", then invoking
385      * this method with the {@code Path} "{@code bar}" will result in the {@code
386      * Path} "{@code dir1/dir2/bar}". If this path does not have a parent path,
387      * or {@code other} is {@link #isAbsolute() absolute}, then this method
388      * returns {@code other}. If {@code other} is an empty path then this method
389      * returns this path's parent, or where this path doesn't have a parent, the
390      * empty path.
391      *
392      * @param   other
393      *          the path to resolve against this path's parent
394      *
395      * @return  the resulting path
396      *
397      * @see #resolve(Path)
398      */
399     Path resolveSibling(Path other);
400 
401     /**
402      * Converts a given path string to a {@code Path} and resolves it against
403      * this path's {@link #getParent parent} path in exactly the manner
404      * specified by the {@link #resolveSibling(Path) resolveSibling} method.
405      *
406      * @param   other
407      *          the path string to resolve against this path's parent
408      *
409      * @return  the resulting path
410      *
411      * @throws  InvalidPathException
412      *          if the path string cannot be converted to a Path.
413      *
414      * @see FileSystem#getPath
415      */
416     Path resolveSibling(String other);
417 
418     /**
419      * Constructs a relative path between this path and a given path.
420      *
421      * <p> Relativization is the inverse of {@link #resolve(Path) resolution}.
422      * This method attempts to construct a {@link #isAbsolute relative} path
423      * that when {@link #resolve(Path) resolved} against this path, yields a
424      * path that locates the same file as the given path. For example, on UNIX,
425      * if this path is {@code "/a/b"} and the given path is {@code "/a/b/c/d"}
426      * then the resulting relative path would be {@code "c/d"}. Where this
427      * path and the given path do not have a {@link #getRoot root} component,
428      * then a relative path can be constructed. A relative path cannot be
429      * constructed if only one of the paths have a root component. Where both
430      * paths have a root component then it is implementation dependent if a
431      * relative path can be constructed. If this path and the given path are
432      * {@link #equals equal} then an <i>empty path</i> is returned.
433      *
434      * <p> For any two {@link #normalize normalized} paths <i>p</i> and
435      * <i>q</i>, where <i>q</i> does not have a root component,
436      * <blockquote>
437      *   <i>p</i><tt>.relativize(</tt><i>p</i><tt>.resolve(</tt><i>q</i><tt>)).equals(</tt><i>q</i><tt>)</tt>
438      * </blockquote>
439      *
440      * <p> When symbolic links are supported, then whether the resulting path,
441      * when resolved against this path, yields a path that can be used to locate
442      * the {@link Files#isSameFile same} file as {@code other} is implementation
443      * dependent. For example, if this path is  {@code "/a/b"} and the given
444      * path is {@code "/a/x"} then the resulting relative path may be {@code
445      * "../x"}. If {@code "b"} is a symbolic link then is implementation
446      * dependent if {@code "a/b/../x"} would locate the same file as {@code "/a/x"}.
447      *
448      * @param   other
449      *          the path to relativize against this path
450      *
451      * @return  the resulting relative path, or an empty path if both paths are
452      *          equal
453      *
454      * @throws  IllegalArgumentException
455      *          if {@code other} is not a {@code Path} that can be relativized
456      *          against this path
457      */
458     Path relativize(Path other);
459 
460     /**
461      * Returns a URI to represent this path.
462      *
463      * <p> This method constructs an absolute {@link URI} with a {@link
464      * URI#getScheme() scheme} equal to the URI scheme that identifies the
465      * provider. The exact form of the scheme specific part is highly provider
466      * dependent.
467      *
468      * <p> In the case of the default provider, the URI is hierarchical with
469      * a {@link URI#getPath() path} component that is absolute. The query and
470      * fragment components are undefined. Whether the authority component is
471      * defined or not is implementation dependent. There is no guarantee that
472      * the {@code URI} may be used to construct a {@link java.io.File java.io.File}.
473      * In particular, if this path represents a Universal Naming Convention (UNC)
474      * path, then the UNC server name may be encoded in the authority component
475      * of the resulting URI. In the case of the default provider, and the file
476      * exists, and it can be determined that the file is a directory, then the
477      * resulting {@code URI} will end with a slash.
478      *
479      * <p> The default provider provides a similar <em>round-trip</em> guarantee
480      * to the {@link java.io.File} class. For a given {@code Path} <i>p</i> it
481      * is guaranteed that
482      * <blockquote><tt>
483      * {@link Paths#get(URI) Paths.get}(</tt><i>p</i><tt>.toUri()).equals(</tt><i>p</i>
484      * <tt>.{@link #toAbsolutePath() toAbsolutePath}())</tt>
485      * </blockquote>
486      * so long as the original {@code Path}, the {@code URI}, and the new {@code
487      * Path} are all created in (possibly different invocations of) the same
488      * Java virtual machine. Whether other providers make any guarantees is
489      * provider specific and therefore unspecified.
490      *
491      * <p> When a file system is constructed to access the contents of a file
492      * as a file system then it is highly implementation specific if the returned
493      * URI represents the given path in the file system or it represents a
494      * <em>compound</em> URI that encodes the URI of the enclosing file system.
495      * A format for compound URIs is not defined in this release; such a scheme
496      * may be added in a future release.
497      *
498      * @return  the URI representing this path
499      *
500      * @throws  java.io.IOError
501      *          if an I/O error occurs obtaining the absolute path, or where a
502      *          file system is constructed to access the contents of a file as
503      *          a file system, and the URI of the enclosing file system cannot be
504      *          obtained
505      *
506      * @throws  SecurityException
507      *          In the case of the default provider, and a security manager
508      *          is installed, the {@link #toAbsolutePath toAbsolutePath} method
509      *          throws a security exception.
510      */
511     URI toUri();
512 
513     /**
514      * Returns a {@code Path} object representing the absolute path of this
515      * path.
516      *
517      * <p> If this path is already {@link Path#isAbsolute absolute} then this
518      * method simply returns this path. Otherwise, this method resolves the path
519      * in an implementation dependent manner, typically by resolving the path
520      * against a file system default directory. Depending on the implementation,
521      * this method may throw an I/O error if the file system is not accessible.
522      *
523      * @return  a {@code Path} object representing the absolute path
524      *
525      * @throws  java.io.IOError
526      *          if an I/O error occurs
527      * @throws  SecurityException
528      *          In the case of the default provider, a security manager
529      *          is installed, and this path is not absolute, then the security
530      *          manager's {@link SecurityManager#checkPropertyAccess(String)
531      *          checkPropertyAccess} method is invoked to check access to the
532      *          system property {@code user.dir}
533      */
534     Path toAbsolutePath();
535 
536     /**
537      * Returns the <em>real</em> path of an existing file.
538      *
539      * <p> The precise definition of this method is implementation dependent but
540      * in general it derives from this path, an {@link #isAbsolute absolute}
541      * path that locates the {@link Files#isSameFile same} file as this path, but
542      * with name elements that represent the actual name of the directories
543      * and the file. For example, where filename comparisons on a file system
544      * are case insensitive then the name elements represent the names in their
545      * actual case. Additionally, the resulting path has redundant name
546      * elements removed.
547      *
548      * <p> If this path is relative then its absolute path is first obtained,
549      * as if by invoking the {@link #toAbsolutePath toAbsolutePath} method.
550      *
551      * <p> The {@code options} array may be used to indicate how symbolic links
552      * are handled. By default, symbolic links are resolved to their final
553      * target. If the option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is
554      * present then this method does not resolve symbolic links.
555      *
556      * Some implementations allow special names such as "{@code ..}" to refer to
557      * the parent directory. When deriving the <em>real path</em>, and a
558      * "{@code ..}" (or equivalent) is preceded by a non-"{@code ..}" name then
559      * an implementation will typically cause both names to be removed. When
560      * not resolving symbolic links and the preceding name is a symbolic link
561      * then the names are only removed if it guaranteed that the resulting path
562      * will locate the same file as this path.
563      *
564      * @param   options
565      *          options indicating how symbolic links are handled
566      *
567      * @return  an absolute path represent the <em>real</em> path of the file
568      *          located by this object
569      *
570      * @throws  IOException
571      *          if the file does not exist or an I/O error occurs
572      * @throws  SecurityException
573      *          In the case of the default provider, and a security manager
574      *          is installed, its {@link SecurityManager#checkRead(String) checkRead}
575      *          method is invoked to check read access to the file, and where
576      *          this path is not absolute, its {@link SecurityManager#checkPropertyAccess(String)
577      *          checkPropertyAccess} method is invoked to check access to the
578      *          system property {@code user.dir}
579      */
580     Path toRealPath(LinkOption... options) throws IOException;
581 
582     /**
583      * Returns a {@link File} object representing this path. Where this {@code
584      * Path} is associated with the default provider, then this method is
585      * equivalent to returning a {@code File} object constructed with the
586      * {@code String} representation of this path.
587      *
588      * <p> If this path was created by invoking the {@code File} {@link
589      * File#toPath toPath} method then there is no guarantee that the {@code
590      * File} object returned by this method is {@link #equals equal} to the
591      * original {@code File}.
592      *
593      * @return  a {@code File} object representing this path
594      *
595      * @throws  UnsupportedOperationException
596      *          if this {@code Path} is not associated with the default provider
597      */
598     File toFile();
599 
600     // -- watchable --
601 
602     /**
603      * Registers the file located by this path with a watch service.
604      *
605      * <p> In this release, this path locates a directory that exists. The
606      * directory is registered with the watch service so that entries in the
607      * directory can be watched. The {@code events} parameter is the events to
608      * register and may contain the following events:
609      * <ul>
610      *   <li>{@link StandardWatchEventKinds#ENTRY_CREATE ENTRY_CREATE} -
611      *       entry created or moved into the directory</li>
612      *   <li>{@link StandardWatchEventKinds#ENTRY_DELETE ENTRY_DELETE} -
613      *        entry deleted or moved out of the directory</li>
614      *   <li>{@link StandardWatchEventKinds#ENTRY_MODIFY ENTRY_MODIFY} -
615      *        entry in directory was modified</li>
616      * </ul>
617      *
618      * <p> The {@link WatchEvent#context context} for these events is the
619      * relative path between the directory located by this path, and the path
620      * that locates the directory entry that is created, deleted, or modified.
621      *
622      * <p> The set of events may include additional implementation specific
623      * event that are not defined by the enum {@link StandardWatchEventKinds}
624      *
625      * <p> The {@code modifiers} parameter specifies <em>modifiers</em> that
626      * qualify how the directory is registered. This release does not define any
627      * <em>standard</em> modifiers. It may contain implementation specific
628      * modifiers.
629      *
630      * <p> Where a file is registered with a watch service by means of a symbolic
631      * link then it is implementation specific if the watch continues to depend
632      * on the existence of the symbolic link after it is registered.
633      *
634      * @param   watcher
635      *          the watch service to which this object is to be registered
636      * @param   events
637      *          the events for which this object should be registered
638      * @param   modifiers
639      *          the modifiers, if any, that modify how the object is registered
640      *
641      * @return  a key representing the registration of this object with the
642      *          given watch service
643      *
644      * @throws  UnsupportedOperationException
645      *          if unsupported events or modifiers are specified
646      * @throws  IllegalArgumentException
647      *          if an invalid combination of events or modifiers is specified
648      * @throws  ClosedWatchServiceException
649      *          if the watch service is closed
650      * @throws  NotDirectoryException
651      *          if the file is registered to watch the entries in a directory
652      *          and the file is not a directory  <i>(optional specific exception)</i>
653      * @throws  IOException
654      *          if an I/O error occurs
655      * @throws  SecurityException
656      *          In the case of the default provider, and a security manager is
657      *          installed, the {@link SecurityManager#checkRead(String) checkRead}
658      *          method is invoked to check read access to the file.
659      */
660     @Override
661     WatchKey register(WatchService watcher,
662                       WatchEvent.Kind<?>[] events,
663                       WatchEvent.Modifier... modifiers)
664         throws IOException;
665 
666     /**
667      * Registers the file located by this path with a watch service.
668      *
669      * <p> An invocation of this method behaves in exactly the same way as the
670      * invocation
671      * <pre>
672      *     watchable.{@link #register(WatchService,WatchEvent.Kind[],WatchEvent.Modifier[]) register}(watcher, events, new WatchEvent.Modifier[0]);
673      * </pre>
674      *
675      * <p> <b>Usage Example:</b>
676      * Suppose we wish to register a directory for entry create, delete, and modify
677      * events:
678      * <pre>
679      *     Path dir = ...
680      *     WatchService watcher = ...
681      *
682      *     WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
683      * </pre>
684      * @param   watcher
685      *          The watch service to which this object is to be registered
686      * @param   events
687      *          The events for which this object should be registered
688      *
689      * @return  A key representing the registration of this object with the
690      *          given watch service
691      *
692      * @throws  UnsupportedOperationException
693      *          If unsupported events are specified
694      * @throws  IllegalArgumentException
695      *          If an invalid combination of events is specified
696      * @throws  ClosedWatchServiceException
697      *          If the watch service is closed
698      * @throws  NotDirectoryException
699      *          If the file is registered to watch the entries in a directory
700      *          and the file is not a directory  <i>(optional specific exception)</i>
701      * @throws  IOException
702      *          If an I/O error occurs
703      * @throws  SecurityException
704      *          In the case of the default provider, and a security manager is
705      *          installed, the {@link SecurityManager#checkRead(String) checkRead}
706      *          method is invoked to check read access to the file.
707      */
708     @Override
709     WatchKey register(WatchService watcher,
710                       WatchEvent.Kind<?>... events)
711         throws IOException;
712 
713     // -- Iterable --
714 
715     /**
716      * Returns an iterator over the name elements of this path.
717      *
718      * <p> The first element returned by the iterator represents the name
719      * element that is closest to the root in the directory hierarchy, the
720      * second element is the next closest, and so on. The last element returned
721      * is the name of the file or directory denoted by this path. The {@link
722      * #getRoot root} component, if present, is not returned by the iterator.
723      *
724      * @return  an iterator over the name elements of this path.
725      */
726     @Override
727     Iterator<Path> iterator();
728 
729     // -- compareTo/equals/hashCode --
730 
731     /**
732      * Compares two abstract paths lexicographically. The ordering defined by
733      * this method is provider specific, and in the case of the default
734      * provider, platform specific. This method does not access the file system
735      * and neither file is required to exist.
736      *
737      * <p> This method may not be used to compare paths that are associated
738      * with different file system providers.
739      *
740      * @param   other  the path compared to this path.
741      *
742      * @return  zero if the argument is {@link #equals equal} to this path, a
743      *          value less than zero if this path is lexicographically less than
744      *          the argument, or a value greater than zero if this path is
745      *          lexicographically greater than the argument
746      *
747      * @throws  ClassCastException
748      *          if the paths are associated with different providers
749      */
750     @Override
751     int compareTo(Path other);
752 
753     /**
754      * Tests this path for equality with the given object.
755      *
756      * <p> If the given object is not a Path, or is a Path associated with a
757      * different {@code FileSystem}, then this method returns {@code false}.
758      *
759      * <p> Whether or not two path are equal depends on the file system
760      * implementation. In some cases the paths are compared without regard
761      * to case, and others are case sensitive. This method does not access the
762      * file system and the file is not required to exist. Where required, the
763      * {@link Files#isSameFile isSameFile} method may be used to check if two
764      * paths locate the same file.
765      *
766      * <p> This method satisfies the general contract of the {@link
767      * java.lang.Object#equals(Object) Object.equals} method. </p>
768      *
769      * @param   other
770      *          the object to which this object is to be compared
771      *
772      * @return  {@code true} if, and only if, the given object is a {@code Path}
773      *          that is identical to this {@code Path}
774      */
775     boolean equals(Object other);
776 
777     /**
778      * Computes a hash code for this path.
779      *
780      * <p> The hash code is based upon the components of the path, and
781      * satisfies the general contract of the {@link Object#hashCode
782      * Object.hashCode} method.
783      *
784      * @return  the hash-code value for this path
785      */
786     int hashCode();
787 
788     /**
789      * Returns the string representation of this path.
790      *
791      * <p> If this path was created by converting a path string using the
792      * {@link FileSystem#getPath getPath} method then the path string returned
793      * by this method may differ from the original String used to create the path.
794      *
795      * <p> The returned path string uses the default name {@link
796      * FileSystem#getSeparator separator} to separate names in the path.
797      *
798      * @return  the string representation of this path
799      */
800     String toString();
801 }