File | Java In A Nutshell, 5th Edition

File

java.io

Java 1.0

serializable comparable

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( )