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This class supports a platform-independent
definition of file and
directory names. It also
provides methods to list the files in a directory; check the
existence, readability, writability, type, size, and modification
time of files and directories; make new directories; rename files and
directories; delete files and directories; and create and delete
temporary and lock files.
The constants
defined by this class are the platform-dependent directory and
path-separator characters, available as a String
and a char.getName( ) returns the
name of the File with any directory names omitted.
getPath( ) returns the full name of the file,
including the directory name. getParent( ) and
getParentFile( ) return the directory that
contains the File; the only difference between the
two methods is that one returns a String, while
the other returns a File. isAbsolute(
) tests whether the File is an
absolute
specification. If not, getAbsolutePath( ) returns
an absolute filename created by appending the relative filename to
the current working directory. getAbsoluteFile( )
returns the equivalent absolute File object.
getCanonicalPath( ) and getCanonicalFile(
) are similar methods: they return an absolute filename or
File object that has been converted to its
system-dependent canonical form. This can be useful
when comparing two File objects to see if they
refer to the same file or directory. In Java 1.4 and later, the
toURI( ) method returns a
java.net.URI object that uses a
file: scheme to name this file.
This file-to-URI transformation can be
reversed by passing a file: URI object to the
File( ) constructor.exists( ),
canWrite( ), canRead( ),
isFile( ), isDirectory( ), and
isHidden( ) perform the obvious tests on the
specified File. length( )
returns the length of the file. lastModified( )
returns the modification time of the file (which should
be used for comparison with other file times only and not interpreted
as any particular time format). setLastModified( )
allows the modification time to be set; setReadOnly(
) makes a file or directory read-only.list( ) returns the
names of all entries in a
directory that are not rejected by an
optional FilenameFilter. listFiles(
) returns an array of File objects that
represent all entries in a directory not rejected by an optional
FilenameFilter or FileFilter.
listRoots( ) returns an array of
File objects representing all root directories on
the system. Unix systems typically have only one
root, / . Windows systems have a different
root for each drive letter: c:\ ,
d:\ , and e:\ , for example.mkdir( ) creates a
directory, and
mkdirs( ) creates all the directories in a
File specification. renameTo( )
renames a file or directory; delete( ) deletes a
file or directory. Prior to Java
1.2, the File class doesn''t
provide any way to create a file; that task is accomplished typically
with FileOutputStream. Two special-purpose file
creation methods have were added in Java 1.2. The static
createTempFile(
) method
returns a File object that refers to a newly
created empty file with a unique name that begins with the specified
prefix (which must be at least three characters long) and ends with
the specified suffix. One version of this method creates the file in
a specified directory, and the other creates it in the system
temporary directory. Applications can use temporary files for any
purpose without worrying about overwriting files belonging to other
applications. The other file-creation method of Java 1.2 is
createNewFile( ). This instance method attempts to
create a new, empty file with the name specified by the
File object. If it succeeds, it returns
TRue. However, if the file already exists, it
returns false. createNewFile( )
works atomically and is therefore useful for
file locking and other mutual-exclusion schemes. When working with
createTempFile( ) or createNewFile(
), consider using deleteOnExit(
) to request that the files be deleted
when the Java VM exits normally.
Figure 9-14. java.io.File
public class File implements Serializable, Comparable<File> {
// Public Constructors
1.4 public File (java.net.URI uri );
public File (String pathname );
public File (File parent , String child );
public File (String parent , String child );
// Public Constants
public static final String pathSeparator ;
public static final char pathSeparatorChar ;
public static final String separator ;
public static final char separatorChar ;
// Public Class Methods
1.2 public static File createTempFile (String prefix , String suffix ) throws IOException;
1.2 public static File createTempFile (String prefix , String suffix , File directory ) throws
IOException;
1.2 public static File[ ] listRoots ( );
// Public Instance Methods
public boolean canRead ( );
public boolean canWrite ( );
1.2 public boolean createNewFile ( ) throws IOException;
public boolean delete ( );
1.2 public void deleteOnExit ( );
public boolean exists ( );
1.2 public File getAbsoluteFile ( );
public String getAbsolutePath ( );
1.2 public File getCanonicalFile ( ) throws IOException;
1.1 public String getCanonicalPath ( ) throws IOException;
public String getName ( );
public String getParent ( );
1.2 public File getParentFile ( );
public String getPath ( );
public boolean isAbsolute ( );
public boolean isDirectory ( );
public boolean isFile ( );
1.2 public boolean isHidden ( );
public long lastModified ( );
public long length ( );
public String[ ] list ( );
public String[ ] list (FilenameFilter filter );
1.2 public File[ ] listFiles ( );
1.2 public File[ ] listFiles (FilenameFilter filter );
1.2 public File[ ] listFiles (FileFilter filter );
public boolean mkdir ( );
public boolean mkdirs ( );
public boolean renameTo (File dest );
1.2 public boolean setLastModified (long time );
1.2 public boolean setReadOnly ( );
1.4 public java.net.URI toURI ( );
1.2 public java.net.URL toURL ( ) throws java.net.MalformedURLException;
// Methods Implementing Comparable
1.2 public int compareTo (File pathname );
// Public Methods Overriding Object
public boolean equals (Object obj );
public int hashCode ( );
public String toString ( );
}Passed To
Too many methods to list.
Returned By
ProcessBuilder.directory( )
