IT. Expert System.

Java Standard Edition (SE)

Path


compact1, compact2, compact3
java.nio.file

Interface Path

  • All Superinterfaces:
    Comparable<Path>, Iterable<Path>, Watchable


    public interface Path
    extends Comparable<Path>, Iterable<Path>, Watchable
    An object that may be used to locate a file in a file system. It will typically represent a system dependent file path.

    A 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 Path can represent a root, a root and a sequence of names, or simply one or more name elements. A 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. Path defines the getFileName, getParent, getRoot, and subpath methods to access the path components or a subsequence of its name elements.

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

    This interface extends Watchable interface so that a directory located by a path can be registered with a 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 Files class to operate on files, directories, and other types of files. For example, suppose we want a BufferedReader to read text from a file "access.log". The file is located in a directory "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 provider are generally interoperable with the java.io.File class. Paths created by other providers are unlikely to be interoperable with the abstract path names represented by java.io.File. The toPath method may be used to obtain a Path from the abstract path name represented by a java.io.File object. The resulting Path can be used to operate on the same file as the java.io.File object. In addition, the toFile method is useful to construct a File from the String representation of a Path.

    Concurrency

    Implementations of this interface are immutable and safe for use by multiple concurrent threads.

    Since:
    1.7
    See Also:
    Paths
    • Method Detail

      • getFileSystem

        FileSystem getFileSystem()
        Returns the file system that created this object.
        Returns:
        the file system that created this object
      • isAbsolute

        boolean isAbsolute()
        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.

        Returns:
        true if, and only if, this path is absolute
      • getRoot

        Path getRoot()
        Returns the root component of this path as a Path object, or null if this path does not have a root component.
        Returns:
        a path representing the root component of this path, or null
      • getFileName

        Path getFileName()
        Returns the name of the file or directory denoted by this path as a Path object. The file name is the farthest element from the root in the directory hierarchy.
        Returns:
        a path representing the name of the file or directory, or null if this path has zero elements
      • getParent

        Path getParent()
        Returns the parent path, or 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 "/a/b/c" is "/a/b", and the parent of "x/y/." is "x/y". This method may be used with the 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);
         
        Returns:
        a path representing the path's parent
      • getNameCount

        int getNameCount()
        Returns the number of name elements in the path.
        Returns:
        the number of elements in the path, or 0 if this path only represents a root component
      • getName

        Path getName(int index)
        Returns a name element of this path as a Path object.

        The 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 0. The element that is farthest from the root has index count-1.

        Parameters:
        index - the index of the element
        Returns:
        the name element
        Throws:
        IllegalArgumentException - if index is negative, index is greater than or equal to the number of elements, or this path has zero name elements
      • subpath

        Path subpath(int beginIndex,
                     int endIndex)
        Returns a relative Path that is a subsequence of the name elements of this path.

        The beginIndex and endIndex parameters specify the subsequence of name elements. The name that is closest to the root in the directory hierarchy has index 0. The name that is farthest from the root has index count-1. The returned Path object has the name elements that begin at beginIndex and extend to the element at index endIndex-1.

        Parameters:
        beginIndex - the index of the first element, inclusive
        endIndex - the index of the last element, exclusive
        Returns:
        a new Path object that is a subsequence of the name elements in this Path
        Throws:
        IllegalArgumentException - if beginIndex is negative, or greater than or equal to the number of elements. If endIndex is less than or equal to beginIndex, or larger than the number of elements.
      • startsWith

        boolean startsWith(Path other)
        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 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 FileSystem to this path then false is returned.

        Parameters:
        other - the given path
        Returns:
        true if this path starts with the given path; otherwise false
      • startsWith

        boolean startsWith(String other)
        Tests if this path starts with a Path, constructed by converting the given path string, in exactly the manner specified by the startsWith(Path) method. On UNIX for example, the path "foo/bar" starts with "foo" and "foo/bar". It does not start with "f" or "fo".
        Parameters:
        other - the given path string
        Returns:
        true if this path starts with the given path; otherwise false
        Throws:
        InvalidPathException - If the path string cannot be converted to a Path.
      • endsWith

        boolean endsWith(Path 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 FileSystem to this path then false is returned.

        Parameters:
        other - the given path
        Returns:
        true if this path ends with the given path; otherwise false
      • endsWith

        boolean endsWith(String other)
        Tests if this path ends with a Path, constructed by converting the given path string, in exactly the manner specified by the endsWith(Path) method. On UNIX for example, the path "foo/bar" ends with "foo/bar" and "bar". It does not end with "r" or "/bar". Note that trailing separators are not taken into account, and so invoking this method on the Path"foo/bar" with the String "bar/" returns true.
        Parameters:
        other - the given path string
        Returns:
        true if this path ends with the given path; otherwise false
        Throws:
        InvalidPathException - If the path string cannot be converted to a Path.
      • normalize

        Path normalize()
        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 "." and ".." are special names used to indicate the current directory and parent directory. In such file systems all occurrences of "." are considered redundant. If a ".." is preceded by a non-".." 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 ".." 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.

        Returns:
        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 Also:
        getParent(), toRealPath(java.nio.file.LinkOption...)
      • resolve

        Path resolve(Path other)
        Resolve the given path against this path.

        If the other parameter is an absolute path then this method trivially returns other. If 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 root component, in which case this method joins the given path to this path and returns a resulting path that ends with the given path. Where the given path has a root component then resolution is highly implementation dependent and therefore unspecified.

        Parameters:
        other - the path to resolve against this path
        Returns:
        the resulting path
        See Also:
        relativize(java.nio.file.Path)
      • resolve

        Path resolve(String other)
        Converts a given path string to a Path and resolves it against this Path in exactly the manner specified by the resolve method. For example, suppose that the name separator is "/" and a path represents "foo/bar", then invoking this method with the path string "gus" will result in the Path "foo/bar/gus".
        Parameters:
        other - the path string to resolve against this path
        Returns:
        the resulting path
        Throws:
        InvalidPathException - if the path string cannot be converted to a Path.
        See Also:
        FileSystem.getPath(java.lang.String, java.lang.String...)
      • resolveSibling

        Path resolveSibling(Path other)
        Resolves the given path against this path's 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 "/" and a path represents "dir1/dir2/foo", then invoking this method with the Path "bar" will result in the Path "dir1/dir2/bar". If this path does not have a parent path, or other is absolute, then this method returns other. If 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.
        Parameters:
        other - the path to resolve against this path's parent
        Returns:
        the resulting path
        See Also:
        resolve(Path)
      • relativize

        Path relativize(Path other)
        Constructs a relative path between this path and a given path.

        Relativization is the inverse of resolution. This method attempts to construct a relative path that when resolved against this path, yields a path that locates the same file as the given path. For example, on UNIX, if this path is "/a/b" and the given path is "/a/b/c/d" then the resulting relative path would be "c/d". Where this path and the given path do not have a 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 equal then an empty path is returned.

        For any two 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 same file as other is implementation dependent. For example, if this path is "/a/b" and the given path is "/a/x" then the resulting relative path may be "../x". If "b" is a symbolic link then is implementation dependent if "a/b/../x" would locate the same file as "/a/x".

        Parameters:
        other - the path to relativize against this path
        Returns:
        the resulting relative path, or an empty path if both paths are equal
        Throws:
        IllegalArgumentException - if other is not a Path that can be relativized against this path
      • toUri

        URI toUri()
        Returns a URI to represent this path.

        This method constructs an absolute URI with a 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 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 URI may be used to construct a 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 URI will end with a slash.

        The default provider provides a similar round-trip guarantee to the File class. For a given Path p it is guaranteed that

        Paths.get(p.toUri()).equals(p .toAbsolutePath())
        so long as the original Path, the URI, and the new 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.

        Returns:
        the URI representing this path
        Throws:
        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
        SecurityException - In the case of the default provider, and a security manager is installed, the toAbsolutePath method throws a security exception.
      • toAbsolutePath

        Path toAbsolutePath()
        Returns a Path object representing the absolute path of this path.

        If this path is already 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.

        Returns:
        a Path object representing the absolute path
        Throws:
        IOError - if an I/O error occurs
        SecurityException - In the case of the default provider, a security manager is installed, and this path is not absolute, then the security manager's checkPropertyAccess method is invoked to check access to the system property user.dir
      • toRealPath

        Path toRealPath(LinkOption... options)
                 throws IOException
        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 absolute path that locates the 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 toAbsolutePath method.

        The 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 NOFOLLOW_LINKS is present then this method does not resolve symbolic links. Some implementations allow special names such as ".." to refer to the parent directory. When deriving the real path, and a ".." (or equivalent) is preceded by a non-".." 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.

        Parameters:
        options - options indicating how symbolic links are handled
        Returns:
        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
        SecurityException - In the case of the default provider, and a security manager is installed, its checkRead method is invoked to check read access to the file, and where this path is not absolute, its checkPropertyAccess method is invoked to check access to the system property user.dir
      • toFile

        File toFile()
        Returns a File object representing this path. Where this Path is associated with the default provider, then this method is equivalent to returning a File object constructed with the String representation of this path.

        If this path was created by invoking the File toPath method then there is no guarantee that the File object returned by this method is equal to the original File.

        Returns:
        a File object representing this path
        Throws:
        UnsupportedOperationException - if this Path is not associated with the default provider
      • register

        WatchKey register(WatchService watcher,
                          WatchEvent.Kind<?>[] events,
                          WatchEvent.Modifier... modifiers)
                   throws IOException
        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 events parameter is the events to register and may contain the following events:

        The 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 StandardWatchEventKinds

        The 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.

        Specified by:
        register in interface Watchable
        Parameters:
        watcher - the watch service to which this object is to be registered
        events - the events for which this object should be registered
        modifiers - the modifiers, if any, that modify how the object is registered
        Returns:
        a key representing the registration of this object with the given watch service
        Throws:
        UnsupportedOperationException - if unsupported events or modifiers are specified
        IllegalArgumentException - if an invalid combination of events or modifiers is specified
        ClosedWatchServiceException - if the watch service is closed
        NotDirectoryException - if the file is registered to watch the entries in a directory and the file is not a directory (optional specific exception)
        IOException - if an I/O error occurs
        SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to the file.
      • register

        WatchKey register(WatchService watcher,
                          WatchEvent.Kind<?>... events)
                   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.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);
         
        Specified by:
        register in interface Watchable
        Parameters:
        watcher - The watch service to which this object is to be registered
        events - The events for which this object should be registered
        Returns:
        A key representing the registration of this object with the given watch service
        Throws:
        UnsupportedOperationException - If unsupported events are specified
        IllegalArgumentException - If an invalid combination of events is specified
        ClosedWatchServiceException - If the watch service is closed
        NotDirectoryException - If the file is registered to watch the entries in a directory and the file is not a directory (optional specific exception)
        IOException - If an I/O error occurs
        SecurityException - In the case of the default provider, and a security manager is installed, the checkRead method is invoked to check read access to the file.
      • iterator

        Iterator<Path> iterator()
        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 root component, if present, is not returned by the iterator.

        Specified by:
        iterator in interface Iterable<Path>
        Returns:
        an iterator over the name elements of this path.
      • compareTo

        int compareTo(Path other)
        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.

        Specified by:
        compareTo in interface Comparable<Path>
        Parameters:
        other - the path compared to this path.
        Returns:
        zero if the argument is 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
      • equals

        boolean equals(Object 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 FileSystem, then this method returns 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 isSameFile method may be used to check if two paths locate the same file.

        This method satisfies the general contract of the Object.equals method.

        Overrides:
        equals in class Object
        Parameters:
        other - the object to which this object is to be compared
        Returns:
        true if, and only if, the given object is a Path that is identical to this Path
        See Also:
        Object.hashCode(), HashMap
      • toString

        String toString()
        Returns the string representation of this path.

        If this path was created by converting a path string using the 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 separator to separate names in the path.

        Overrides:
        toString in class Object
        Returns:
        the string representation of this path


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