JDK8/Java8源码在线阅读
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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.
*
* <p> 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 <em>root component</em>, that identifies a file system
* hierarchy, may also be present. The name element that is <em>farthest</em>
* 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 <i>empty path</i> if it consists
* solely of one name element that is empty. Accessing a file using an
* <i>empty path</i> 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.
*
* <p> 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.
*
* <p> 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. </p>
*
* <p> <b>WARNING:</b> 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. </p>
*
* <h2>Accessing Files</h2>
* <p> 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.
* <pre>
* Path path = FileSystems.getDefault().getPath("logs", "access.log");
* BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8);
* </pre>
*
* <a name="interop"></a><h2>Interoperability</h2>
* <p> 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}.
*
* <h2>Concurrency</h2>
* <p> Implementations of this interface are immutable and safe for use by
* multiple concurrent threads.
*
* @since 1.7
* @see Paths
*/
public interface Path
extends Comparable<Path>, Iterable<Path>, 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.
*
* <p> 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 <em>farthest</em> 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 <em>parent path</em>, or {@code null} if this path does not
* have a parent.
*
* <p> The parent of this path object consists of this path's root
* component, if any, and each element in the path except for the
* <em>farthest</em> 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
* <em>shell-like</em> navigation is required.
*
* <p> If this path has one or more elements, and no root component, then
* this method is equivalent to evaluating the expression:
* <blockquote><pre>
* subpath(0, getNameCount()-1);
* </pre></blockquote>
*
* @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.
*
* <p> The {@code index} parameter is the index of the name element to return.
* The element that is <em>closest</em> to the root in the directory hierarchy
* has index {@code 0}. The element that is <em>farthest</em> 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.
*
* <p> The {@code beginIndex} and {@code endIndex} parameters specify the
* subsequence of name elements. The name that is <em>closest</em> to the root
* in the directory hierarchy has index {@code 0}. The name that is
* <em>farthest</em> 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.
*
* <p> This path <em>starts</em> with the given path if this path's root
* component <em>starts</em> 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.
*
* <p> 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.
*
* <p> 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.
*
* <p> If the given path has <em>N</em> elements, and no root component,
* and this path has <em>N</em> or more elements, then this path ends with
* the given path if the last <em>N</em> elements of each path, starting at
* the element farthest from the root, are equal.
*
* <p> If the given path has a root component then this path ends with the
* given path if the root component of this path <em>ends with</em> 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.
*
* <p> 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.
*
* <p> The precise definition of this method is implementation dependent but
* in general it derives from this path, a path that does not contain
* <em>redundant</em> 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).
*
* <p> 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.
*
* <p> If the {@code other} parameter is an {@link #isAbsolute() absolute}
* path then this method trivially returns {@code other}. If {@code other}
* is an <i>empty path</i> 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
* <em>joins</em> 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 <i>replaced</i> 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.
*
* <p> 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 <i>empty path</i> is returned.
*
* <p> For any two {@link #normalize normalized} paths <i>p</i> and
* <i>q</i>, where <i>q</i> does not have a root component,
* <blockquote>
* <i>p</i><tt>.relativize(</tt><i>p</i><tt>.resolve(</tt><i>q</i><tt>)).equals(</tt><i>q</i><tt>)</tt>
* </blockquote>
*
* <p> 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.
*
* <p> 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.
*
* <p> 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.
*
* <p> The default provider provides a similar <em>round-trip</em> guarantee
* to the {@link java.io.File} class. For a given {@code Path} <i>p</i> it
* is guaranteed that
* <blockquote><tt>
* {@link Paths#get(URI) Paths.get}(</tt><i>p</i><tt>.toUri()).equals(</tt><i>p</i>
* <tt>.{@link #toAbsolutePath() toAbsolutePath}())</tt>
* </blockquote>
* 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.
*
* <p> 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
* <em>compound</em> 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.
*
* <p> 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 <em>real</em> path of an existing file.
*
* <p> 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.
*
* <p> If this path is relative then its absolute path is first obtained,
* as if by invoking the {@link #toAbsolutePath toAbsolutePath} method.
*
* <p> 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 <em>real path</em>, 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 <em>real</em> 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.
*
* <p> 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.
*
* <p> 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:
* <ul>
* <li>{@link StandardWatchEventKinds#ENTRY_CREATE ENTRY_CREATE} -
* entry created or moved into the directory</li>
* <li>{@link StandardWatchEventKinds#ENTRY_DELETE ENTRY_DELETE} -
* entry deleted or moved out of the directory</li>
* <li>{@link StandardWatchEventKinds#ENTRY_MODIFY ENTRY_MODIFY} -
* entry in directory was modified</li>
* </ul>
*
* <p> 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.
*
* <p> The set of events may include additional implementation specific
* event that are not defined by the enum {@link StandardWatchEventKinds}
*
* <p> The {@code modifiers} parameter specifies <em>modifiers</em> that
* qualify how the directory is registered. This release does not define any
* <em>standard</em> modifiers. It may contain implementation specific
* modifiers.
*
* <p> 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 <i>(optional specific exception)</i>
* @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.
*
* <p> An invocation of this method behaves in exactly the same way as the
* invocation
* <pre>
* watchable.{@link #register(WatchService,WatchEvent.Kind[],WatchEvent.Modifier[]) register}(watcher, events, new WatchEvent.Modifier[0]);
* </pre>
*
* <p> <b>Usage Example:</b>
* Suppose we wish to register a directory for entry create, delete, and modify
* events:
* <pre>
* Path dir = ...
* WatchService watcher = ...
*
* WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
* </pre>
* @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 <i>(optional specific exception)</i>
* @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
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