java.io.File
File
object contains a path, which is a character string that can be used to identify
a file within a file system. A path is assumed to consist of two parts, the directory
and the file name, separated by the last occurrence within the path of a
particular character known as the separator character. Some methods provide
access to parts of the path string; other methods operate on the file that is identified
by the path string. The details of such operations on files are to some extent
dependent on the implementation of the host file system. The File
class is
designed to provide a set of abstract operations that are reasonably portable across
otherwise incompatible file systems.
public classFile
{ public static final Stringseparator
= System.getProperty("file.separator"); public static final charseparatorChar
= separator.charAt(0); public static final StringpathSeparator
= System.getProperty("path.separator"); public static final charpathSeparatorChar
= pathSeparator.charAt(0); publicFile
(String path) throws NullPointerException; publicFile
(String dirname, String name) throws NullPointerException publicFile
(File dir, String name) throws NullPointerException public StringtoString
(); public booleanequals
(Object obj); public inthashCode
(); public StringgetName
(); public StringgetPath
(); public StringgetAbsolutePath
(); public StringgetParent
(); public native booleanisAbsolute
(); public booleanexists
() throws SecurityException; public booleancanRead
() throws SecurityException; public booleancanWrite
() throws SecurityException; public booleanisFile
() throws SecurityException; public booleanisDirectory
() throws SecurityException; public longlastModified
() throws SecurityException; public longlength
() throws SecurityException; public booleanmkdir
() throws SecurityException; public booleanmkdirs
() throws SecurityException; public String[]list
() throws SecurityException; public String[]list
(FilenameFilter filter) throws SecurityException; public booleanrenameTo
(File dest) throws SecurityException; public booleandelete
() throws SecurityException; }
22.24.1 public static final String
separator
= System.getProperty("file.separator");
This string should consist of a single character, whose value is also available in
the field separatorChar
; the string is provided merely for convenience.
22.24.2 public static final char
separatorChar
= separator.charAt(0);
The last occurrence of this character in a path string is assumed to separate the
directory part of the path from the file name part of the path. On UNIX systems
this character is typically '/'
.
22.24.3 public static final String
pathSeparator
= System.getProperty("path.separator");
This string should consist of a single character, whose value is also available in
the field pathSeparatorChar
; the string is provided merely for convenience.
22.24.4 public static final char
pathSeparatorChar
= pathSeparator.charAt(0);
The first occurrence of this character in a string is sometimes assumed to separate
a host name from a path name. On UNIX systems this character is typically ':'
.
22.24.5 public
File
(String path) throws NullPointerException
This constructor initializes a newly created File
so that it represents the path indicated
by the argument path
.
If the path
is null
, a NullPointerException
is thrown.
22.24.6 public
File
(String dirname, String name)
throws NullPointerException
This constructor initializes a newly created File
so that it represents the path
whose directory part is specified by the argument dirname
and whose file name
part is specified by the argument name
. If the dirname
argument is null
, the name
is used as the path; otherwise the concatenation of dirname
, the separatorChar
(§22.24.2), and the name
is used as the path.
If the name
is null
, a NullPointerException
is thrown.
22.24.7 public
File
(File dir, String name)
throws NullPointerException
This constructor initializes a newly created File
so that it represents the path
whose directory part is specified by the File
object dir
and whose file name part
is specified by the argument name
.
If the name
is null
, a NullPointerException
is thrown.
22.24.8 public String
toString
()
The result is a String
equal to the path represented by this File
object.
Overrides the toString
method of Object
(§20.1.2).
22.24.9 public boolean
equals
(Object obj)
The result is true
if and only if the argument is not null
and is a File
object that
represents the same path as this File
object. In other words, two File
objects are
equal if and only if the strings returned by the getPath
method (§22.24.12) are
equal.
Overrides the equals
method of Object
(§20.1.3).
22.24.10 public int
hashCode
()
The hash code of this File
object is equal to the exclusive OR of the hash code of
its path string and the decimal value 1234321
:
this.getPath().hashcode() ^ 1234321Overrides the
hashCode
method of Object
(§20.1.4).22.24.11 public String
getName
()
If the path string contains the separatorChar
character (§22.24.2), this method
returns the substring of the path that follows the last occurrence of the separator
character; otherwise, the entire path string is returned.
22.24.12 public String
getPath
()
The result is a String
equal to the path represented by this File
object.
22.24.13 public String
getAbsolutePath
()
The result is a String
equal to the result of converting to "absolute form" the path
represented by this File
object.
22.24.14 public String
getParent
()
If the path has a parent directory, a String
representing the path of that parent
directory is returned; otherwise, null
is returned.
22.24.15 public boolean
isAbsolute
()
The result is true
if and only if the path represented by the File object is in absolute
form, indicating a complete name that starts from the root of the directory
hierarchy, rather than a name relative to some implied directory.
22.24.16 public boolean
exists
() throws SecurityException
First, if there is a security manager, its checkRead
method (§20.17.19) is called
with the path represented by this File
object as its argument.
The result is true
if and only if the file system actually contains a file that is specified by the path of the File
object.
22.24.17 public boolean
canRead
() throws SecurityException
First, if there is a security manager, its checkRead
method (§20.17.19) is called
with the path represented by this File
object as its argument.
The result is true
if and only if both of the following are true:
File
object.
22.24.18 public boolean
canWrite
() throws SecurityException
First, if there is a security manager, its checkWrite
method (§20.17.21) is called
with the path represented by this File
object as its argument.
The result is true
if and only if both of the following are true:
File
object.
22.24.19 public boolean
isFile
() throws SecurityException
First, if there is a security manager, its checkRead
method (§20.17.19) is called
with the path represented by this File
object as its argument.
The result is true
if and only if both of the following are true:
File
object.
22.24.20 public boolean
isDirectory
() throws SecurityException
First, if there is a security manager, its checkRead
method (§20.17.19) is called
with the path represented by this File
object as its argument.
The result is true
if and only if both of the following are true:
File
object.
22.24.21 public long
lastModified
() throws SecurityException
First, if there is a security manager, its checkRead
method (§20.17.19) is called
with the path represented by this File
object as its argument.
An abstract modification time is returned. If two values returned by this method are compared, whether for the same file or for two different files, the smaller value represents an earlier modification time. Abstract modification times do not necessarily bear any relationship, even monotonicity, to times returned by the method System.currentTimeMillis
(§20.18.6).
22.24.22 public long
length
() throws SecurityException
First, if there is a security manager, its checkRead
method (§20.17.19) is called
with the path represented by this File
object as its argument.
The length of the file, measured in bytes, is returned.
22.24.23 public boolean
mkdir
() throws SecurityException
First, if there is a security manager, its checkWrite
method (§20.17.21) is called
with the path represented by this File
object as its argument.
An attempt is made to create the directory specified by the path represented by this File
object; the result is true if and only if the creation operation succeeds.
22.24.24 public boolean
mkdirs
() throws SecurityException
First, if there is a security manager, its checkRead
method (§20.17.19) is called
with the path represented by this File
object as its argument.
If the directory name represented by this File
object has a parent directory name (§22.24.14), an attempt is first made to create the parent directory; if this attempt fails, the result is false
. Otherwise, once the parent directory has been determined to exist, or if the path has no parent, an attempt is made to create the directory specified by this File
object. The result is true
if and only if the creation operation succeeds.
22.24.25 public String[]
list
() throws SecurityException
First, if there is a security manager, its checkRead
method (§20.17.19) is called
with the path represented by this File
object as its argument.
If the path represented by this File
object does not correspond to a directory in the file system, then null
is returned. Otherwise, an array of strings is returned, one for each file in the directory (on UNIX systems, the names ".
" and "..
" are not included). Each string is a file name, not a complete path. There is no guarantee that the strings will appear in any particular order within the array; for example, they are not guaranteed to appear in alphabetical order.
22.24.26 public String[]
list
(FilenameFilter filter)
throws SecurityException
First, if there is a security manager, its checkRead
method (§20.17.19) is called
with the path represented by this File
object as its argument.
If the path represented by this File
object does not correspond to a directory in the file system, then null
is returned. Otherwise, an array of strings is returned, one for each file in the directory (on UNIX systems, the names ".
" and "..
" are not included) whose name satisfies the given filter
. Each string is a file name, not a complete path. There is no guarantee that the strings will appear in any particular order within the array; for example, they are not guaranteed to appear in alphabetical order. A file name satisfies the filter if and only if the value true
results when the accept
method (§22.25.1) of the filter is called with this File
object and the name as arguments.
22.24.27 public boolean
renameTo
(File dest)
throws SecurityException
First, if there is a security manager, its checkWrite
method (§20.17.21) is called
twice, first with the path represented by this File
object as its argument and again
with the path of dest
as its argument.
An attempt is made to rename the file specified by the path represented by this File
object to the name specified by dest
; the result is true
if and only if the renaming operation succeeds.
22.24.28 public boolean
delete
() throws SecurityException
First, if there is a security manager, its checkDelete
method (§20.17.22) is called
with the path represented by this File
object as its argument.
An attempt is made to delete the file specified by the path represented by this File
object; the result is true
if and only if the deletion operation succeeds.
java.io.FilenameFilter
list
method (§22.24.26) of class File
requires, as an argument, an object
that implements the FilenameFilter
interface. The only purpose of such an
object is to provide a method accept
that decides which files should appear in the
generated directory listing.
public interfaceFilenameFilter
{ public booleanaccept
(File dir, String name); }
22.25.1 public boolean
accept
(File dir, String name)
This method should return true
if and only if the given file named name
in the
directory dir
is to appear in the final list of files generated by the list
method
(§22.24.26) of class File
.
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Java Language Specification (HTML generated by Suzette Pelouch on February 24, 1998)
Copyright © 1996 Sun Microsystems, Inc.
All rights reserved
Please send any comments or corrections to doug.kramer@sun.com