/* * Copyright (c) 2007, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.nio.file; import java.io.File; import java.io.IOException; import java.net.URI; import java.util.Iterator; /** * An object that may be used to locate a file in a file system. It will * typically represent a system dependent file path. * *

A {@code Path} represents a path that is hierarchical and composed of a * sequence of directory and file name elements separated by a special separator * or delimiter. A root component, that identifies a file system * hierarchy, may also be present. The name element that is farthest * from the root of the directory hierarchy is the name of a file or directory. * The other name elements are directory names. A {@code Path} can represent a * root, a root and a sequence of names, or simply one or more name elements. * A {@code Path} is considered to be an empty path if it consists * solely of one name element that is empty. Accessing a file using an * empty path is equivalent to accessing the default directory of the * file system. {@code Path} defines the {@link #getFileName() getFileName}, * {@link #getParent getParent}, {@link #getRoot getRoot}, and {@link #subpath * subpath} methods to access the path components or a subsequence of its name * elements. * *

In addition to accessing the components of a path, a {@code Path} also * defines the {@link #resolve(Path) resolve} and {@link #resolveSibling(Path) * resolveSibling} methods to combine paths. The {@link #relativize relativize} * method that can be used to construct a relative path between two paths. * Paths can be {@link #compareTo compared}, and tested against each other using * the {@link #startsWith startsWith} and {@link #endsWith endsWith} methods. * *

This interface extends {@link Watchable} interface so that a directory * located by a path can be {@link #register registered} with a {@link * WatchService} and entries in the directory watched.

* *

WARNING: This interface is only intended to be implemented by * those developing custom file system implementations. Methods may be added to * this interface in future releases.

* *

Accessing Files

*

Paths may be used with the {@link Files} class to operate on files, * directories, and other types of files. For example, suppose we want a {@link * java.io.BufferedReader} to read text from a file "{@code access.log}". The * file is located in a directory "{@code logs}" relative to the current working * directory and is UTF-8 encoded. *

 *     Path path = FileSystems.getDefault().getPath("logs", "access.log");
 *     BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8);
 * 
* *

Interoperability

*

Paths associated with the default {@link * java.nio.file.spi.FileSystemProvider provider} are generally interoperable * with the {@link java.io.File java.io.File} class. Paths created by other * providers are unlikely to be interoperable with the abstract path names * represented by {@code java.io.File}. The {@link java.io.File#toPath toPath} * method may be used to obtain a {@code Path} from the abstract path name * represented by a {@code java.io.File} object. The resulting {@code Path} can * be used to operate on the same file as the {@code java.io.File} object. In * addition, the {@link #toFile toFile} method is useful to construct a {@code * File} from the {@code String} representation of a {@code Path}. * *

Concurrency

*

Implementations of this interface are immutable and safe for use by * multiple concurrent threads. * * @since 1.7 * @see Paths */ public interface Path extends Comparable, Iterable, Watchable { /** * Returns the file system that created this object. * * @return the file system that created this object */ FileSystem getFileSystem(); /** * Tells whether or not this path is absolute. * *

An absolute path is complete in that it doesn't need to be combined * with other path information in order to locate a file. * * @return {@code true} if, and only if, this path is absolute */ boolean isAbsolute(); /** * Returns the root component of this path as a {@code Path} object, * or {@code null} if this path does not have a root component. * * @return a path representing the root component of this path, * or {@code null} */ Path getRoot(); /** * Returns the name of the file or directory denoted by this path as a * {@code Path} object. The file name is the farthest element from * the root in the directory hierarchy. * * @return a path representing the name of the file or directory, or * {@code null} if this path has zero elements */ Path getFileName(); /** * Returns the parent path, or {@code null} if this path does not * have a parent. * *

The parent of this path object consists of this path's root * component, if any, and each element in the path except for the * farthest from the root in the directory hierarchy. This method * does not access the file system; the path or its parent may not exist. * Furthermore, this method does not eliminate special names such as "." * and ".." that may be used in some implementations. On UNIX for example, * the parent of "{@code /a/b/c}" is "{@code /a/b}", and the parent of * {@code "x/y/.}" is "{@code x/y}". This method may be used with the {@link * #normalize normalize} method, to eliminate redundant names, for cases where * shell-like navigation is required. * *

If this path has one or more elements, and no root component, then * this method is equivalent to evaluating the expression: *

     * subpath(0, getNameCount()-1);
     * 
* * @return a path representing the path's parent */ Path getParent(); /** * Returns the number of name elements in the path. * * @return the number of elements in the path, or {@code 0} if this path * only represents a root component */ int getNameCount(); /** * Returns a name element of this path as a {@code Path} object. * *

The {@code index} parameter is the index of the name element to return. * The element that is closest to the root in the directory hierarchy * has index {@code 0}. The element that is farthest from the root * has index {@link #getNameCount count}{@code -1}. * * @param index * the index of the element * * @return the name element * * @throws IllegalArgumentException * if {@code index} is negative, {@code index} is greater than or * equal to the number of elements, or this path has zero name * elements */ Path getName(int index); /** * Returns a relative {@code Path} that is a subsequence of the name * elements of this path. * *

The {@code beginIndex} and {@code endIndex} parameters specify the * subsequence of name elements. The name that is closest to the root * in the directory hierarchy has index {@code 0}. The name that is * farthest from the root has index {@link #getNameCount * count}{@code -1}. The returned {@code Path} object has the name elements * that begin at {@code beginIndex} and extend to the element at index {@code * endIndex-1}. * * @param beginIndex * the index of the first element, inclusive * @param endIndex * the index of the last element, exclusive * * @return a new {@code Path} object that is a subsequence of the name * elements in this {@code Path} * * @throws IllegalArgumentException * if {@code beginIndex} is negative, or greater than or equal to * the number of elements. If {@code endIndex} is less than or * equal to {@code beginIndex}, or larger than the number of elements. */ Path subpath(int beginIndex, int endIndex); /** * Tests if this path starts with the given path. * *

This path starts with the given path if this path's root * component starts with the root component of the given path, * and this path starts with the same name elements as the given path. * If the given path has more name elements than this path then {@code false} * is returned. * *

Whether or not the root component of this path starts with the root * component of the given path is file system specific. If this path does * not have a root component and the given path has a root component then * this path does not start with the given path. * *

If the given path is associated with a different {@code FileSystem} * to this path then {@code false} is returned. * * @param other * the given path * * @return {@code true} if this path starts with the given path; otherwise * {@code false} */ boolean startsWith(Path other); /** * Tests if this path starts with a {@code Path}, constructed by converting * the given path string, in exactly the manner specified by the {@link * #startsWith(Path) startsWith(Path)} method. On UNIX for example, the path * "{@code foo/bar}" starts with "{@code foo}" and "{@code foo/bar}". It * does not start with "{@code f}" or "{@code fo}". * * @param other * the given path string * * @return {@code true} if this path starts with the given path; otherwise * {@code false} * * @throws InvalidPathException * If the path string cannot be converted to a Path. */ boolean startsWith(String other); /** * Tests if this path ends with the given path. * *

If the given path has N elements, and no root component, * and this path has N or more elements, then this path ends with * the given path if the last N elements of each path, starting at * the element farthest from the root, are equal. * *

If the given path has a root component then this path ends with the * given path if the root component of this path ends with the root * component of the given path, and the corresponding elements of both paths * are equal. Whether or not the root component of this path ends with the * root component of the given path is file system specific. If this path * does not have a root component and the given path has a root component * then this path does not end with the given path. * *

If the given path is associated with a different {@code FileSystem} * to this path then {@code false} is returned. * * @param other * the given path * * @return {@code true} if this path ends with the given path; otherwise * {@code false} */ boolean endsWith(Path other); /** * Tests if this path ends with a {@code Path}, constructed by converting * the given path string, in exactly the manner specified by the {@link * #endsWith(Path) endsWith(Path)} method. On UNIX for example, the path * "{@code foo/bar}" ends with "{@code foo/bar}" and "{@code bar}". It does * not end with "{@code r}" or "{@code /bar}". Note that trailing separators * are not taken into account, and so invoking this method on the {@code * Path}"{@code foo/bar}" with the {@code String} "{@code bar/}" returns * {@code true}. * * @param other * the given path string * * @return {@code true} if this path ends with the given path; otherwise * {@code false} * * @throws InvalidPathException * If the path string cannot be converted to a Path. */ boolean endsWith(String other); /** * Returns a path that is this path with redundant name elements eliminated. * *

The precise definition of this method is implementation dependent but * in general it derives from this path, a path that does not contain * redundant name elements. In many file systems, the "{@code .}" * and "{@code ..}" are special names used to indicate the current directory * and parent directory. In such file systems all occurrences of "{@code .}" * are considered redundant. If a "{@code ..}" is preceded by a * non-"{@code ..}" name then both names are considered redundant (the * process to identify such names is repeated until it is no longer * applicable). * *

This method does not access the file system; the path may not locate * a file that exists. Eliminating "{@code ..}" and a preceding name from a * path may result in the path that locates a different file than the original * path. This can arise when the preceding name is a symbolic link. * * @return the resulting path or this path if it does not contain * redundant name elements; an empty path is returned if this path * does have a root component and all name elements are redundant * * @see #getParent * @see #toRealPath */ Path normalize(); // -- resolution and relativization -- /** * Resolve the given path against this path. * *

If the {@code other} parameter is an {@link #isAbsolute() absolute} * path then this method trivially returns {@code other}. If {@code other} * is an empty path then this method trivially returns this path. * Otherwise this method considers this path to be a directory and resolves * the given path against this path. In the simplest case, the given path * does not have a {@link #getRoot root} component, in which case this method * joins the given path to this path and returns a resulting path * that {@link #endsWith ends} with the given path. Where the given path has * a root component then resolution is highly implementation dependent and * therefore unspecified. * * @param other * the path to resolve against this path * * @return the resulting path * * @see #relativize */ Path resolve(Path other); /** * Converts a given path string to a {@code Path} and resolves it against * this {@code Path} in exactly the manner specified by the {@link * #resolve(Path) resolve} method. For example, suppose that the name * separator is "{@code /}" and a path represents "{@code foo/bar}", then * invoking this method with the path string "{@code gus}" will result in * the {@code Path} "{@code foo/bar/gus}". * * @param other * the path string to resolve against this path * * @return the resulting path * * @throws InvalidPathException * if the path string cannot be converted to a Path. * * @see FileSystem#getPath */ Path resolve(String other); /** * Resolves the given path against this path's {@link #getParent parent} * path. This is useful where a file name needs to be replaced with * another file name. For example, suppose that the name separator is * "{@code /}" and a path represents "{@code dir1/dir2/foo}", then invoking * this method with the {@code Path} "{@code bar}" will result in the {@code * Path} "{@code dir1/dir2/bar}". If this path does not have a parent path, * or {@code other} is {@link #isAbsolute() absolute}, then this method * returns {@code other}. If {@code other} is an empty path then this method * returns this path's parent, or where this path doesn't have a parent, the * empty path. * * @param other * the path to resolve against this path's parent * * @return the resulting path * * @see #resolve(Path) */ Path resolveSibling(Path other); /** * Converts a given path string to a {@code Path} and resolves it against * this path's {@link #getParent parent} path in exactly the manner * specified by the {@link #resolveSibling(Path) resolveSibling} method. * * @param other * the path string to resolve against this path's parent * * @return the resulting path * * @throws InvalidPathException * if the path string cannot be converted to a Path. * * @see FileSystem#getPath */ Path resolveSibling(String other); /** * Constructs a relative path between this path and a given path. * *

Relativization is the inverse of {@link #resolve(Path) resolution}. * This method attempts to construct a {@link #isAbsolute relative} path * that when {@link #resolve(Path) resolved} against this path, yields a * path that locates the same file as the given path. For example, on UNIX, * if this path is {@code "/a/b"} and the given path is {@code "/a/b/c/d"} * then the resulting relative path would be {@code "c/d"}. Where this * path and the given path do not have a {@link #getRoot root} component, * then a relative path can be constructed. A relative path cannot be * constructed if only one of the paths have a root component. Where both * paths have a root component then it is implementation dependent if a * relative path can be constructed. If this path and the given path are * {@link #equals equal} then an empty path is returned. * *

For any two {@link #normalize normalized} paths p and * q, where q does not have a root component, *

* p.relativize(p.resolve(q)).equals(q) *
* *

When symbolic links are supported, then whether the resulting path, * when resolved against this path, yields a path that can be used to locate * the {@link Files#isSameFile same} file as {@code other} is implementation * dependent. For example, if this path is {@code "/a/b"} and the given * path is {@code "/a/x"} then the resulting relative path may be {@code * "../x"}. If {@code "b"} is a symbolic link then is implementation * dependent if {@code "a/b/../x"} would locate the same file as {@code "/a/x"}. * * @param other * the path to relativize against this path * * @return the resulting relative path, or an empty path if both paths are * equal * * @throws IllegalArgumentException * if {@code other} is not a {@code Path} that can be relativized * against this path */ Path relativize(Path other); /** * Returns a URI to represent this path. * *

This method constructs an absolute {@link URI} with a {@link * URI#getScheme() scheme} equal to the URI scheme that identifies the * provider. The exact form of the scheme specific part is highly provider * dependent. * *

In the case of the default provider, the URI is hierarchical with * a {@link URI#getPath() path} component that is absolute. The query and * fragment components are undefined. Whether the authority component is * defined or not is implementation dependent. There is no guarantee that * the {@code URI} may be used to construct a {@link java.io.File java.io.File}. * In particular, if this path represents a Universal Naming Convention (UNC) * path, then the UNC server name may be encoded in the authority component * of the resulting URI. In the case of the default provider, and the file * exists, and it can be determined that the file is a directory, then the * resulting {@code URI} will end with a slash. * *

The default provider provides a similar round-trip guarantee * to the {@link java.io.File} class. For a given {@code Path} p it * is guaranteed that *

* {@link Paths#get(URI) Paths.get}(p.toUri()).equals(p * .{@link #toAbsolutePath() toAbsolutePath}()) *
* so long as the original {@code Path}, the {@code URI}, and the new {@code * Path} are all created in (possibly different invocations of) the same * Java virtual machine. Whether other providers make any guarantees is * provider specific and therefore unspecified. * *

When a file system is constructed to access the contents of a file * as a file system then it is highly implementation specific if the returned * URI represents the given path in the file system or it represents a * compound URI that encodes the URI of the enclosing file system. * A format for compound URIs is not defined in this release; such a scheme * may be added in a future release. * * @return the URI representing this path * * @throws java.io.IOError * if an I/O error occurs obtaining the absolute path, or where a * file system is constructed to access the contents of a file as * a file system, and the URI of the enclosing file system cannot be * obtained * * @throws SecurityException * In the case of the default provider, and a security manager * is installed, the {@link #toAbsolutePath toAbsolutePath} method * throws a security exception. */ URI toUri(); /** * Returns a {@code Path} object representing the absolute path of this * path. * *

If this path is already {@link Path#isAbsolute absolute} then this * method simply returns this path. Otherwise, this method resolves the path * in an implementation dependent manner, typically by resolving the path * against a file system default directory. Depending on the implementation, * this method may throw an I/O error if the file system is not accessible. * * @return a {@code Path} object representing the absolute path * * @throws java.io.IOError * if an I/O error occurs * @throws SecurityException * In the case of the default provider, a security manager * is installed, and this path is not absolute, then the security * manager's {@link SecurityManager#checkPropertyAccess(String) * checkPropertyAccess} method is invoked to check access to the * system property {@code user.dir} */ Path toAbsolutePath(); /** * Returns the real path of an existing file. * *

The precise definition of this method is implementation dependent but * in general it derives from this path, an {@link #isAbsolute absolute} * path that locates the {@link Files#isSameFile same} file as this path, but * with name elements that represent the actual name of the directories * and the file. For example, where filename comparisons on a file system * are case insensitive then the name elements represent the names in their * actual case. Additionally, the resulting path has redundant name * elements removed. * *

If this path is relative then its absolute path is first obtained, * as if by invoking the {@link #toAbsolutePath toAbsolutePath} method. * *

The {@code options} array may be used to indicate how symbolic links * are handled. By default, symbolic links are resolved to their final * target. If the option {@link LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} is * present then this method does not resolve symbolic links. * * Some implementations allow special names such as "{@code ..}" to refer to * the parent directory. When deriving the real path, and a * "{@code ..}" (or equivalent) is preceded by a non-"{@code ..}" name then * an implementation will typically cause both names to be removed. When * not resolving symbolic links and the preceding name is a symbolic link * then the names are only removed if it guaranteed that the resulting path * will locate the same file as this path. * * @param options * options indicating how symbolic links are handled * * @return an absolute path represent the real path of the file * located by this object * * @throws IOException * if the file does not exist or an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager * is installed, its {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the file, and where * this path is not absolute, its {@link SecurityManager#checkPropertyAccess(String) * checkPropertyAccess} method is invoked to check access to the * system property {@code user.dir} */ Path toRealPath(LinkOption... options) throws IOException; /** * Returns a {@link File} object representing this path. Where this {@code * Path} is associated with the default provider, then this method is * equivalent to returning a {@code File} object constructed with the * {@code String} representation of this path. * *

If this path was created by invoking the {@code File} {@link * File#toPath toPath} method then there is no guarantee that the {@code * File} object returned by this method is {@link #equals equal} to the * original {@code File}. * * @return a {@code File} object representing this path * * @throws UnsupportedOperationException * if this {@code Path} is not associated with the default provider */ File toFile(); // -- watchable -- /** * Registers the file located by this path with a watch service. * *

In this release, this path locates a directory that exists. The * directory is registered with the watch service so that entries in the * directory can be watched. The {@code events} parameter is the events to * register and may contain the following events: *

* *

The {@link WatchEvent#context context} for these events is the * relative path between the directory located by this path, and the path * that locates the directory entry that is created, deleted, or modified. * *

The set of events may include additional implementation specific * event that are not defined by the enum {@link StandardWatchEventKinds} * *

The {@code modifiers} parameter specifies modifiers that * qualify how the directory is registered. This release does not define any * standard modifiers. It may contain implementation specific * modifiers. * *

Where a file is registered with a watch service by means of a symbolic * link then it is implementation specific if the watch continues to depend * on the existence of the symbolic link after it is registered. * * @param watcher * the watch service to which this object is to be registered * @param events * the events for which this object should be registered * @param modifiers * the modifiers, if any, that modify how the object is registered * * @return a key representing the registration of this object with the * given watch service * * @throws UnsupportedOperationException * if unsupported events or modifiers are specified * @throws IllegalArgumentException * if an invalid combination of events or modifiers is specified * @throws ClosedWatchServiceException * if the watch service is closed * @throws NotDirectoryException * if the file is registered to watch the entries in a directory * and the file is not a directory (optional specific exception) * @throws IOException * if an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the file. */ @Override WatchKey register(WatchService watcher, WatchEvent.Kind[] events, WatchEvent.Modifier... modifiers) throws IOException; /** * Registers the file located by this path with a watch service. * *

An invocation of this method behaves in exactly the same way as the * invocation *

     *     watchable.{@link #register(WatchService,WatchEvent.Kind[],WatchEvent.Modifier[]) register}(watcher, events, new WatchEvent.Modifier[0]);
     * 
* *

Usage Example: * Suppose we wish to register a directory for entry create, delete, and modify * events: *

     *     Path dir = ...
     *     WatchService watcher = ...
     *
     *     WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
     * 
* @param watcher * The watch service to which this object is to be registered * @param events * The events for which this object should be registered * * @return A key representing the registration of this object with the * given watch service * * @throws UnsupportedOperationException * If unsupported events are specified * @throws IllegalArgumentException * If an invalid combination of events is specified * @throws ClosedWatchServiceException * If the watch service is closed * @throws NotDirectoryException * If the file is registered to watch the entries in a directory * and the file is not a directory (optional specific exception) * @throws IOException * If an I/O error occurs * @throws SecurityException * In the case of the default provider, and a security manager is * installed, the {@link SecurityManager#checkRead(String) checkRead} * method is invoked to check read access to the file. */ @Override WatchKey register(WatchService watcher, WatchEvent.Kind... events) throws IOException; // -- Iterable -- /** * Returns an iterator over the name elements of this path. * *

The first element returned by the iterator represents the name * element that is closest to the root in the directory hierarchy, the * second element is the next closest, and so on. The last element returned * is the name of the file or directory denoted by this path. The {@link * #getRoot root} component, if present, is not returned by the iterator. * * @return an iterator over the name elements of this path. */ @Override Iterator iterator(); // -- compareTo/equals/hashCode -- /** * Compares two abstract paths lexicographically. The ordering defined by * this method is provider specific, and in the case of the default * provider, platform specific. This method does not access the file system * and neither file is required to exist. * *

This method may not be used to compare paths that are associated * with different file system providers. * * @param other the path compared to this path. * * @return zero if the argument is {@link #equals equal} to this path, a * value less than zero if this path is lexicographically less than * the argument, or a value greater than zero if this path is * lexicographically greater than the argument * * @throws ClassCastException * if the paths are associated with different providers */ @Override int compareTo(Path other); /** * Tests this path for equality with the given object. * *

If the given object is not a Path, or is a Path associated with a * different {@code FileSystem}, then this method returns {@code false}. * *

Whether or not two path are equal depends on the file system * implementation. In some cases the paths are compared without regard * to case, and others are case sensitive. This method does not access the * file system and the file is not required to exist. Where required, the * {@link Files#isSameFile isSameFile} method may be used to check if two * paths locate the same file. * *

This method satisfies the general contract of the {@link * java.lang.Object#equals(Object) Object.equals} method.

* * @param other * the object to which this object is to be compared * * @return {@code true} if, and only if, the given object is a {@code Path} * that is identical to this {@code Path} */ boolean equals(Object other); /** * Computes a hash code for this path. * *

The hash code is based upon the components of the path, and * satisfies the general contract of the {@link Object#hashCode * Object.hashCode} method. * * @return the hash-code value for this path */ int hashCode(); /** * Returns the string representation of this path. * *

If this path was created by converting a path string using the * {@link FileSystem#getPath getPath} method then the path string returned * by this method may differ from the original String used to create the path. * *

The returned path string uses the default name {@link * FileSystem#getSeparator separator} to separate names in the path. * * @return the string representation of this path */ String toString(); }