[JAVA API] java.io.File

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java.io

Class File

• java.lang.Object
• • java.io.File

• All Implemented Interfaces:

  Serializable, Comparable<File>

  ---

  
  

  public class File
  extends Object
  implements Serializable, Comparable<File>

  An abstract representation of file and directory pathnames.

  User interfaces and operating systems use system-dependent pathname strings to name files and directories. This class presents an abstract, system-independent view of hierarchical pathnames. An abstract pathname has two components:

  1. An optional system-dependent prefix string, such as a disk-drive specifier, "/" for the UNIX root directory, or "\\\\" for a Microsoft Windows UNC pathname, and
  2. A sequence of zero or more string names.

  The first name in an abstract pathname may be a directory name or, in the case of Microsoft Windows UNC pathnames, a hostname. Each subsequent name in an abstract pathname denotes a directory; the last name may denote either a directory or a file. The empty abstract pathname has no prefix and an empty name sequence.

  The conversion of a pathname string to or from an abstract pathname is inherently system-dependent. When an abstract pathname is converted into a pathname string, each name is separated from the next by a single copy of the default separator character. The default name-separator character is defined by the system property file.separator, and is made available in the public static fields separator and separatorChar of this class. When a pathname string is converted into an abstract pathname, the names within it may be separated by the default name-separator character or by any other name-separator character that is supported by the underlying system.

  A pathname, whether abstract or in string form, may be either absolute or relative. An absolute pathname is complete in that no other information is required in order to locate the file that it denotes. A relative pathname, in contrast, must be interpreted in terms of information taken from some other pathname. By default the classes in the java.io package always resolve relative pathnames against the current user directory. This directory is named by the system property user.dir, and is typically the directory in which the Java virtual machine was invoked.

  The parent of an abstract pathname may be obtained by invoking the getParent() method of this class and consists of the pathname's prefix and each name in the pathname's name sequence except for the last. Each directory's absolute pathname is an ancestor of any File object with an absolute abstract pathname which begins with the directory's absolute pathname. For example, the directory denoted by the abstract pathname "/usr" is an ancestor of the directory denoted by the pathname "/usr/local/bin".

  The prefix concept is used to handle root directories on UNIX platforms, and drive specifiers, root directories and UNC pathnames on Microsoft Windows platforms, as follows:

  • For UNIX platforms, the prefix of an absolute pathname is always "/". Relative pathnames have no prefix. The abstract pathname denoting the root directory has the prefix "/" and an empty name sequence.
  • For Microsoft Windows platforms, the prefix of a pathname that contains a drive specifier consists of the drive letter followed by ":" and possibly followed by "\\" if the pathname is absolute. The prefix of a UNC pathname is "\\\\"; the hostname and the share name are the first two names in the name sequence. A relative pathname that does not specify a drive has no prefix.

  Instances of this class may or may not denote an actual file-system object such as a file or a directory. If it does denote such an object then that object resides in a partition. A partition is an operating system-specific portion of storage for a file system. A single storage device (e.g. a physical disk-drive, flash memory, CD-ROM) may contain multiple partitions. The object, if any, will reside on the partition named by some ancestor of the absolute form of this pathname.

  A file system may implement restrictions to certain operations on the actual file-system object, such as reading, writing, and executing. These restrictions are collectively known as access permissions. The file system may have multiple sets of access permissions on a single object. For example, one set may apply to the object's owner, and another may apply to all other users. The access permissions on an object may cause some methods in this class to fail.

  Instances of the File class are immutable; that is, once created, the abstract pathname represented by a File object will never change.

  Interoperability with java.nio.file package

  The java.nio.file package defines interfaces and classes for the Java virtual machine to access files, file attributes, and file systems. This API may be used to overcome many of the limitations of the java.io.File class. The toPath method may be used to obtain a Path that uses the abstract path represented by a File object to locate a file. The resulting Path may be used with the Files class to provide more efficient and extensive access to additional file operations, file attributes, and I/O exceptions to help diagnose errors when an operation on a file fails.

  Since:

  JDK1.0

  See Also:

  Serialized Form

• • Field Summary

    Fields 

    Modifier and Type	Field and Description
    static String	pathSeparator The system-dependent path-separator character, represented as a string for convenience.
    static char	pathSeparatorChar The system-dependent path-separator character.
    static String	separator The system-dependent default name-separator character, represented as a string for convenience.
    static char	separatorChar The system-dependent default name-separator character.

  • Constructor Summary

    Constructors 

    Constructor and Description
    File(File parent, String child) Creates a new File instance from a parent abstract pathname and a child pathname string.
    File(String pathname) Creates a new File instance by converting the given pathname string into an abstract pathname.
    File(String parent, String child) Creates a new File instance from a parent pathname string and a child pathname string.
    File(URI uri) Creates a new File instance by converting the given file: URI into an abstract pathname.

  • Method Summary

    Methods 

    Modifier and Type	Method and Description
    boolean	canExecute() Tests whether the application can execute the file denoted by this abstract pathname.
    boolean	canRead() Tests whether the application can read the file denoted by this abstract pathname.
    boolean	canWrite() Tests whether the application can modify the file denoted by this abstract pathname.
    int	compareTo(File pathname) Compares two abstract pathnames lexicographically.
    boolean	createNewFile() Atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist.
    static File	createTempFile(String prefix, String suffix) Creates an empty file in the default temporary-file directory, using the given prefix and suffix to generate its name.
    static File	createTempFile(String prefix, String suffix, File directory) Creates a new empty file in the specified directory, using the given prefix and suffix strings to generate its name.
    boolean	delete() Deletes the file or directory denoted by this abstract pathname.
    void	deleteOnExit() Requests that the file or directory denoted by this abstract pathname be deleted when the virtual machine terminates.
    boolean	equals(Object obj) Tests this abstract pathname for equality with the given object.
    boolean	exists() Tests whether the file or directory denoted by this abstract pathname exists.
    File	getAbsoluteFile() Returns the absolute form of this abstract pathname.
    String	getAbsolutePath() Returns the absolute pathname string of this abstract pathname.
    File	getCanonicalFile() Returns the canonical form of this abstract pathname.
    String	getCanonicalPath() Returns the canonical pathname string of this abstract pathname.
    long	getFreeSpace() Returns the number of unallocated bytes in the partition named by this abstract path name.
    String	getName() Returns the name of the file or directory denoted by this abstract pathname.
    String	getParent() Returns the pathname string of this abstract pathname's parent, or null if this pathname does not name a parent directory.
    File	getParentFile() Returns the abstract pathname of this abstract pathname's parent, or null if this pathname does not name a parent directory.
    String	getPath() Converts this abstract pathname into a pathname string.
    long	getTotalSpace() Returns the size of the partition named by this abstract pathname.
    long	getUsableSpace() Returns the number of bytes available to this virtual machine on the partition named by this abstract pathname.
    int	hashCode() Computes a hash code for this abstract pathname.
    boolean	isAbsolute() Tests whether this abstract pathname is absolute.
    boolean	isDirectory() Tests whether the file denoted by this abstract pathname is a directory.
    boolean	isFile() Tests whether the file denoted by this abstract pathname is a normal file.
    boolean	isHidden() Tests whether the file named by this abstract pathname is a hidden file.
    long	lastModified() Returns the time that the file denoted by this abstract pathname was last modified.
    long	length() Returns the length of the file denoted by this abstract pathname.
    String[]	list() Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname.
    String[]	list(FilenameFilter filter) Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.
    File[]	listFiles() Returns an array of abstract pathnames denoting the files in the directory denoted by this abstract pathname.
    File[]	listFiles(FileFilter filter) Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.
    File[]	listFiles(FilenameFilter filter) Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.
    static File[]	listRoots() List the available filesystem roots.
    boolean	mkdir() Creates the directory named by this abstract pathname.
    boolean	mkdirs() Creates the directory named by this abstract pathname, including any necessary but nonexistent parent directories.
    boolean	renameTo(File dest) Renames the file denoted by this abstract pathname.
    boolean	setExecutable(boolean executable) A convenience method to set the owner's execute permission for this abstract pathname.
    boolean	setExecutable(boolean executable, boolean ownerOnly) Sets the owner's or everybody's execute permission for this abstract pathname.
    boolean	setLastModified(long time) Sets the last-modified time of the file or directory named by this abstract pathname.
    boolean	setReadable(boolean readable) A convenience method to set the owner's read permission for this abstract pathname.
    boolean	setReadable(boolean readable, boolean ownerOnly) Sets the owner's or everybody's read permission for this abstract pathname.
    boolean	setReadOnly() Marks the file or directory named by this abstract pathname so that only read operations are allowed.
    boolean	setWritable(boolean writable) A convenience method to set the owner's write permission for this abstract pathname.
    boolean	setWritable(boolean writable, boolean ownerOnly) Sets the owner's or everybody's write permission for this abstract pathname.
    Path	toPath() Returns a java.nio.file.Path object constructed from the this abstract path.
    String	toString() Returns the pathname string of this abstract pathname.
    URI	toURI() Constructs a file: URI that represents this abstract pathname.
    URL	toURL() Deprecated.  This method does not automatically escape characters that are illegal in URLs. It is recommended that new code convert an abstract pathname into a URL by first converting it into a URI, via the toURI method, and then converting the URI into a URL via the URI.toURL method.

    • Methods inherited from class java.lang.Object

      clone, finalize, getClass, notify, notifyAll, wait, wait, wait