File (Java Platform SE 8 )
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Java&&PlatformStandard&Ed.&8
Class File
java.io.File
All Implemented Interfaces:
public class File
implements , &&
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.
abstract pathname has two components:
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
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 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
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
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
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.
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.
storage device (e.g. a physical disk-drive, flash memory, CD-ROM) may
contain multiple partitions.
The object, if any, will reside on the
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.
restrictions are collectively known as access permissions.
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 that is, once
created, the abstract pathname represented by a File object
will never change.
Interoperability with java.nio.file package
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.
method may be used to obtain a
that uses the abstract path represented by a File object to
locate a file. The resulting Path may be used with the
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.
Field Summary
Modifier and Type
Field and Description
The system-dependent path-separator character, represented as a string
for convenience.
static char
The system-dependent path-separator character.
The system-dependent default name-separator character, represented as a
string for convenience.
static char
The system-dependent default name-separator character.
Constructor Summary
Constructors&
Constructor and Description
Creates a new File instance from a parent abstract
pathname and a child pathname string.
(&pathname)
Creates a new File instance by converting the given
pathname string into an abstract pathname.
Creates a new File instance from a parent pathname string
and a child pathname string.
Creates a new File instance by converting the given
file: URI into an abstract pathname.
Method Summary
All Methods&&&&&
Modifier and Type
Method and Description
Tests whether the application can execute the file denoted by this
abstract pathname.
Tests whether the application can read the file denoted by this
abstract pathname.
Tests whether the application can modify the file denoted by this
abstract pathname.
(&pathname)
Compares two abstract pathnames lexicographically.
Atomically creates a new, empty file named by this abstract pathname if
and only if a file with this name does not yet exist.
Creates an empty file in the default temporary-file directory, using
the given prefix and suffix to generate its name.
&directory)
Creates a new empty file in the specified directory, using the
given prefix and suffix strings to generate its name.
Deletes the file or directory denoted by this abstract pathname.
Requests that the file or directory denoted by this abstract
pathname be deleted when the virtual machine terminates.
Tests this abstract pathname for equality with the given object.
Tests whether the file or directory denoted by this abstract pathname
Returns the absolute form of this abstract pathname.
Returns the absolute pathname string of this abstract pathname.
Returns the canonical form of this abstract pathname.
Returns the canonical pathname string of this abstract pathname.
Returns the number of unallocated bytes in the partition named by this abstract path name.
Returns the name of the file or directory denoted by this abstract
Returns the pathname string of this abstract pathname's parent, or
null if this pathname does not name a parent directory.
Returns the abstract pathname of this abstract pathname's parent,
or null if this pathname does not name a parent
directory.
Converts this abstract pathname into a pathname string.
Returns the size of the partition
abstract pathname.
Returns the number of bytes available to this virtual machine on the
by this abstract pathname.
Computes a hash code for this abstract pathname.
Tests whether this abstract pathname is absolute.
Tests whether the file denoted by this abstract pathname is a
directory.
Tests whether the file denoted by this abstract pathname is a normal
Tests whether the file named by this abstract pathname is a hidden
Returns the time that the file denoted by this abstract pathname was
last modified.
Returns the length of the file denoted by this abstract pathname.
Returns an array of strings naming the files and directories in the
directory denoted by this abstract pathname.
Returns an array of strings naming the files and directories in the
directory denoted by this abstract pathname that satisfy the specified
Returns an array of abstract pathnames denoting the files in the
directory denoted by this abstract pathname.
Returns an array of abstract pathnames denoting the files and
directories in the directory denoted by this abstract pathname that
satisfy the specified 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.
List the available filesystem roots.
Creates the directory named by this abstract pathname.
Creates the directory named by this abstract pathname, including any
necessary but nonexistent parent directories.
Renames the file denoted by this abstract pathname.
(boolean&executable)
A convenience method to set the owner's execute permission for this
abstract pathname.
(boolean&executable,
boolean&ownerOnly)
Sets the owner's or everybody's execute permission for this abstract
(long&time)
Sets the last-modified time of the file or directory named by this
abstract pathname.
(boolean&readable)
A convenience method to set the owner's read permission for this abstract
(boolean&readable,
boolean&ownerOnly)
Sets the owner's or everybody's read permission for this abstract
Marks the file or directory named by this abstract pathname so that
only read operations are allowed.
(boolean&writable)
A convenience method to set the owner's write permission for this abstract
(boolean&writable,
boolean&ownerOnly)
Sets the owner's or everybody's write permission for this abstract
object constructed from the
this abstract path.
Returns the pathname string of this abstract pathname.
Constructs a file: URI that represents this abstract pathname.
Deprecated.&
Methods inherited from class&java.lang.
, , , , , , ,
Field Detail
separatorChar
public static final&char separatorChar
The system-dependent default name-separator character.
This field is
initialized to contain the first character of the value of the system
property file.separator.
On UNIX systems the value of this
field is '/'; on Microsoft Windows systems it is '\\'.
public static final& separator
The system-dependent default name-separator character, represented as a
string for convenience.
This string contains a single character, namely
pathSeparatorChar
public static final&char pathSeparatorChar
The system-dependent path-separator character.
This field is
initialized to contain the first character of the value of the system
property path.separator.
This character is used to
separate filenames in a sequence of files given as a path list.
On UNIX systems, this character is ':'; on Microsoft Windows systems it
pathSeparator
public static final& pathSeparator
The system-dependent path-separator character, represented as a string
for convenience.
This string contains a single character, namely
Constructor Detail
public&File(&pathname)
Creates a new File instance by converting the given
pathname string into an abstract pathname.
If the given string is
the empty string, then the result is the empty abstract pathname.
Parameters:
pathname - A pathname string
- If the pathname argument is null
public&File(&parent,
Creates a new File instance from a parent pathname string
and a child pathname string.
If parent is null then the new
File instance is created as if by invoking the
single-argument File constructor on the given
child pathname string.
Otherwise the parent pathname string is taken to denote
a directory, and the child pathname string is taken to
denote either a directory or a file.
If the child pathname
string is absolute then it is converted into a relative pathname in a
system-dependent way.
If parent is the empty string then
the new File instance is created by converting
child into an abstract pathname and resolving the result
against a system-dependent default directory.
Otherwise each pathname
string is converted into an abstract pathname and the child abstract
pathname is resolved against the parent.
Parameters:
parent - The parent pathname string
child - The child pathname string
- If child is null
public&File(&parent,
Creates a new File instance from a parent abstract
pathname and a child pathname string.
If parent is null then the new
File instance is created as if by invoking the
single-argument File constructor on the given
child pathname string.
Otherwise the parent abstract pathname is taken to
denote a directory, and the child pathname string is taken
to denote either a directory or a file.
If the child
pathname string is absolute then it is converted into a relative
pathname in a system-dependent way.
If parent is the empty
abstract pathname then the new File instance is created by
converting child into an abstract pathname and resolving
the result against a system-dependent default directory.
Otherwise each
pathname string is converted into an abstract pathname and the child
abstract pathname is resolved against the parent.
Parameters:
parent - The parent abstract pathname
child - The child pathname string
- If child is null
public&File(&uri)
Creates a new File instance by converting the given
file: URI into an abstract pathname.
The exact form of a file: URI is system-dependent, hence
the transformation performed by this constructor is also
system-dependent.
For a given abstract pathname f it is guaranteed that
new File(&f.()).equals(&f.())
so long as the original abstract pathname, the URI, and the new abstract
pathname are all created in (possibly different invocations of) the same
Java virtual machine.
This relationship typically does not hold,
however, when a file: URI that is created in a virtual machine
on one operating system is converted into an abstract pathname in a
virtual machine on a different operating system.
Parameters:
uri - An absolute, hierarchical URI with a scheme equal to
"file", a non-empty path component, and undefined
authority, query, and fragment components
- If uri is null
- If the preconditions on the parameter do not hold
Method Detail
public&&getName()
Returns the name of the file or directory denoted by this abstract
This is just the last name in the pathname's name
If the pathname's name sequence is empty, then the empty
string is returned.
The name of the file or directory denoted by this abstract
pathname, or the empty string if this pathname's name sequence
public&&getParent()
Returns the pathname string of this abstract pathname's parent, or
null if this pathname does not name a parent directory.
The parent of an abstract pathname consists of the
pathname's prefix, if any, and each name in the pathname's name
sequence except for the last.
If the name sequence is empty then
the pathname does not name a parent directory.
The pathname string of the parent directory named by this
abstract pathname, or null if this pathname
does not name a parent
getParentFile
public&&getParentFile()
Returns the abstract pathname of this abstract pathname's parent,
or null if this pathname does not name a parent
directory.
The parent of an abstract pathname consists of the
pathname's prefix, if any, and each name in the pathname's name
sequence except for the last.
If the name sequence is empty then
the pathname does not name a parent directory.
The abstract pathname of the parent directory named by this
abstract pathname, or null if this pathname
does not name a parent
public&&getPath()
Converts this abstract pathname into a pathname string.
The resulting
string uses the
separate the names in the name sequence.
The string form of this abstract pathname
isAbsolute
public&boolean&isAbsolute()
Tests whether this abstract pathname is absolute.
The definition of
absolute pathname is system dependent.
On UNIX systems, a pathname is
absolute if its prefix is "/".
On Microsoft Windows systems, a
pathname is absolute if its prefix is a drive specifier followed by
"\\", or if its prefix is "\\\\".
true if this abstract pathname is absolute,
false otherwise
getAbsolutePath
public&&getAbsolutePath()
Returns the absolute pathname string of this abstract pathname.
If this abstract pathname is already absolute, then the pathname
string is simply returned as if by the
If this abstract pathname is the empty abstract pathname then
the pathname string of the current user directory, which is named by the
system property user.dir, is returned.
Otherwise this
pathname is resolved in a system-dependent way.
On UNIX systems, a
relative pathname is made absolute by resolving it against the current
user directory.
On Microsoft Windows systems, a relative pathname is made absolute
by resolving it against the current directory of the drive named by the
pathname, if not, it is resolved against the current user
directory.
The absolute pathname string denoting the same file or
directory as this abstract pathname
- If a required system property value cannot be accessed.
getAbsoluteFile
public&&getAbsoluteFile()
Returns the absolute form of this abstract pathname.
Equivalent to
new&File(this.).
The absolute abstract pathname denoting the same file or
directory as this abstract pathname
- If a required system property value cannot be accessed.
getCanonicalPath
public&&getCanonicalPath()
Returns the canonical pathname string of this abstract pathname.
A canonical pathname is both absolute and unique.
The precise
definition of canonical form is system-dependent.
This method first
converts this pathname to absolute form if necessary, as if by invoking the
method, and then maps it to its unique form in a
system-dependent way.
This typically involves removing redundant names
such as "." and ".." from the pathname, resolving
symbolic links (on UNIX platforms), and converting drive letters to a
standard case (on Microsoft Windows platforms).
Every pathname that denotes an existing file or directory has a
unique canonical form.
Every pathname that denotes a nonexistent file
or directory also has a unique canonical form.
The canonical form of
the pathname of a nonexistent file or directory may be different from
the canonical form of the same pathname after the file or directory is
Similarly, the canonical form of the pathname of an existing
file or directory may be different from the canonical form of the same
pathname after the file or directory is deleted.
The canonical pathname string denoting the same file or
directory as this abstract pathname
- If an I/O error occurs, which is possible because the
construction of the canonical pathname may require
filesystem queries
- If a required system property value cannot be accessed, or
if a security manager exists and its
method denies
read access to the file
getCanonicalFile
public&&getCanonicalFile()
Returns the canonical form of this abstract pathname.
Equivalent to
new&File(this.).
The canonical pathname string denoting the same file or
directory as this abstract pathname
- If an I/O error occurs, which is possible because the
construction of the canonical pathname may require
filesystem queries
- If a required system property value cannot be accessed, or
if a security manager exists and its
method denies
read access to the file
public&&toURL()
Deprecated.&
Converts this abstract pathname into a file: URL.
exact form of the URL is system-dependent.
If it can be determined that
the file denoted by this abstract pathname is a directory, then the
resulting URL will end with a slash.
A URL object representing the equivalent file URL
- If the path cannot be parsed as a URL
public&&toURI()
Constructs a file: URI that represents this abstract pathname.
The exact form of the URI is system-dependent.
If it can be
determined that the file denoted by this abstract pathname is a
directory, then the resulting URI will end with a slash.
For a given abstract pathname f, it is guaranteed that
new (&f.toURI()).equals(&f.())
so long as the original abstract pathname, the URI, and the new abstract
pathname are all created in (possibly different invocations of) the same
Java virtual machine.
Due to the system-dependent nature of abstract
pathnames, however, this relationship typically does not hold when a
file: URI that is created in a virtual machine on one operating
system is converted into an abstract pathname in a virtual machine on a
different operating system.
Note that when this abstract pathname represents a UNC pathname then
all components of the UNC (including the server name component) are encoded
in the URI path. The authority component is undefined, meaning
that it is represented as null. The
class defines the
method to encode the server name in the authority
component of the resulting URI. The
may be used to obtain a Path representing this abstract pathname.
An absolute, hierarchical URI with a scheme equal to
"file", a path representing this abstract pathname,
and undefined authority, query, and fragment components
- If a required system property value cannot
be accessed.
public&boolean&canRead()
Tests whether the application can read the file denoted by this
abstract pathname. On some platforms it may be possible to start the
Java virtual machine with special privileges that allow it to read
files that are marked as unreadable. Consequently this method may return
true even though the file does not have read permissions.
true if and only if the file specified by this
abstract pathname exists and can be read by the
false otherwise
- If a security manager exists and its
method denies read access to the file
public&boolean&canWrite()
Tests whether the application can modify the file denoted by this
abstract pathname. On some platforms it may be possible to start the
Java virtual machine with special privileges that allow it to modify
files that are marked read-only. Consequently this method may return
true even though the file is marked read-only.
true if and only if the file system actually
contains a file denoted by this abstract pathname and
the application is allowed
false otherwise.
- If a security manager exists and its
method denies write access to the file
public&boolean&exists()
Tests whether the file or directory denoted by this abstract pathname
true if and only if the file or directory denoted
by this abst false otherwise
- If a security manager exists and its
method denies read access to the file or directory
isDirectory
public&boolean&isDirectory()
Tests whether the file denoted by this abstract pathname is a
directory.
Where it is required to distinguish an I/O exception from the case
that the file is not a directory, or where several attributes of the
same file are required at the same time, then the
method may be used.
true if and only if the file denoted by this
abstract pathname exists and
false otherwise
- If a security manager exists and its
method denies read access to the file
public&boolean&isFile()
Tests whether the file denoted by this abstract pathname is a normal
A file is normal if it is not a directory and, in
addition, satisfies other system-dependent criteria.
Any non-directory
file created by a Java application is guaranteed to be a normal file.
Where it is required to distinguish an I/O exception from the case
that the file is not a normal file, or where several attributes of the
same file are required at the same time, then the
method may be used.
true if and only if the file denoted by this
abstract pathname exists and
false otherwise
- If a security manager exists and its
method denies read access to the file
public&boolean&isHidden()
Tests whether the file named by this abstract pathname is a hidden
The exact definition of hidden is system-dependent.
UNIX systems, a file is considered to be hidden if its name begins with
a period character ('.').
On Microsoft Windows systems, a file is
considered to be hidden if it has been marked as such in the filesystem.
true if and only if the file denoted by this
abstract pathname is hidden according to the conventions of the
underlying platform
- If a security manager exists and its
method denies read access to the file
lastModified
public&long&lastModified()
Returns the time that the file denoted by this abstract pathname was
last modified.
Where it is required to distinguish an I/O exception from the case
where 0L is returned, or where several attributes of the
same file are required at the same time, or where the time of last
access or the creation time are required, then the
method may be used.
A long value representing the time the file was
last modified, measured in milliseconds since the epoch
(00:00:00 GMT, January 1, 1970), or 0L if the
file does not exist or if an I/O error occurs
- If a security manager exists and its
method denies read access to the file
public&long&length()
Returns the length of the file denoted by this abstract pathname.
The return value is unspecified if this pathname denotes a directory.
Where it is required to distinguish an I/O exception from the case
that 0L is returned, or where several attributes of the same file
are required at the same time, then the
method may be used.
The length, in bytes, of the file denoted by this abstract
pathname, or 0L if the file does not exist.
operating systems may return 0L for pathnames
denoting system-dependent entities such as devices or pipes.
- If a security manager exists and its
method denies read access to the file
createNewFile
public&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.
The check for the
existence of the file and the creation of the file if it does not exist
are a single operation that is atomic with respect to all other
filesystem activities that might affect the file.
Note: this method should not be used for file-locking, as
the resulting protocol cannot be made to work reliably. The
facility should be used instead.
true if the named file does not exist and was
false if the named file
already exists
- If an I/O error occurred
- If a security manager exists and its
method denies write access to the file
public&boolean&delete()
Deletes the file or directory denoted by this abstract pathname.
this pathname denotes a directory, then the directory must be empty in
order to be deleted.
Note that the
class defines the
method to throw an
when a file cannot be deleted. This is useful for error reporting and to
diagnose why a file cannot be deleted.
true if and only if the file or directory is
false otherwise
- If a security manager exists and its
method denies
delete access to the file
deleteOnExit
public&void&deleteOnExit()
Requests that the file or directory denoted by this abstract
pathname be deleted when the virtual machine terminates.
Files (or directories) are deleted in the reverse order that
they are registered. Invoking this method to delete a file or
directory that is already registered for deletion has no effect.
Deletion will be attempted only for normal termination of the
virtual machine, as defined by the Java Language Specification.
Once deletion has been requested, it is not possible to cancel the
This method should therefore be used with care.
Note: this method should not be used for file-locking, as
the resulting protocol cannot be made to work reliably. The
facility should be used instead.
- If a security manager exists and its
method denies
delete access to the file
public&[]&list()
Returns an array of strings naming the files and directories in the
directory denoted by this abstract pathname.
If this abstract pathname does not denote a directory, then this
method returns null.
Otherwise an array of strings is
returned, one for each file or directory in the directory.
denoting the directory itself and the directory's parent directory are
not included in the result.
Each string is a file name rather than a
complete path.
There is no guarantee that the name strings in the resulting array
will appear i they are not, in particular,
guaranteed to appear in alphabetical order.
Note that the
class defines the
open a directory and iterate over the names of the files in the directory.
This may use less resources when working with very large directories, and
may be more responsive when working with remote directories.
An array of strings naming the files and directories in the
directory denoted by this abstract pathname.
The array will be
empty if the directory is empty.
Returns null if
this abstract pathname does not denote a directory, or if an
I/O error occurs.
- If a security manager exists and its
method denies read access to
the directory
public&[]&list(&filter)
Returns an array of strings naming the files and directories in the
directory denoted by this abstract pathname that satisfy the specified
The behavior of this method is the same as that of the
method, except that the strings in the returned array
must satisfy the filter.
If the given filter is null
then all names are accepted.
Otherwise, a name satisfies the filter if
and only if the value true results when the
of the filter is invoked on this abstract pathname and the name of a
file or directory in the directory that it denotes.
Parameters:
filter - A filename filter
An array of strings naming the files and directories in the
directory denoted by this abstract pathname that were accepted
by the given filter.
The array will be empty if the
directory is empty or if no names were accepted by the filter.
Returns null if this abstract pathname does not denote
a directory, or if an I/O error occurs.
- If a security manager exists and its
method denies read access to
the directory
public&[]&listFiles()
Returns an array of abstract pathnames denoting the files in the
directory denoted by this abstract pathname.
If this abstract pathname does not denote a directory, then this
method returns null.
Otherwise an array of File objects
is returned, one for each file or directory in the directory.
denoting the directory itself and the directory's parent directory are
not included in the result.
Each resulting abstract pathname is
constructed from this abstract pathname using the
constructor.
Therefore if this
pathname is absolute then each resulting
pathname is relative then each resulting pathname will be relative to
the same directory.
There is no guarantee that the name strings in the resulting array
will appear i they are not, in particular,
guaranteed to appear in alphabetical order.
Note that the
class defines the
to open a directory and iterate over the names of the files in the
directory. This may use less resources when working with very large
directories.
An array of abstract pathnames denoting the files and
directories in the directory denoted by this abstract pathname.
The array will be empty if the directory is empty.
null if this abstract pathname does not denote a
directory, or if an I/O error occurs.
- If a security manager exists and its
method denies read access to
the directory
public&[]&listFiles(&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.
The behavior of this method is the same
as that of the
method, except that the pathnames in
the returned array must satisfy the filter.
If the given filter
is null then all pathnames are accepted.
Otherwise, a pathname
satisfies the filter if and only if the value true results when
method of the filter is
invoked on this abstract pathname and the name of a file or directory in
the directory that it denotes.
Parameters:
filter - A filename filter
An array of abstract pathnames denoting the files and
directories in the directory denoted by this abstract pathname.
The array will be empty if the directory is empty.
null if this abstract pathname does not denote a
directory, or if an I/O error occurs.
- If a security manager exists and its
method denies read access to
the directory
public&[]&listFiles(&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.
The behavior of this method is the same
as that of the
method, except that the pathnames in
the returned array must satisfy the filter.
If the given filter
is null then all pathnames are accepted.
Otherwise, a pathname
satisfies the filter if and only if the value true results when
method of the
filter is invoked on the pathname.
Parameters:
filter - A file filter
An array of abstract pathnames denoting the files and
directories in the directory denoted by this abstract pathname.
The array will be empty if the directory is empty.
null if this abstract pathname does not denote a
directory, or if an I/O error occurs.
- If a security manager exists and its
method denies read access to
the directory
public&boolean&mkdir()
Creates the directory named by this abstract pathname.
true if and only if the directory was
false otherwise
- If a security manager exists and its
method does not permit the named directory to be created
public&boolean&mkdirs()
Creates the directory named by this abstract pathname, including any
necessary but nonexistent parent directories.
Note that if this
operation fails it may have succeeded in creating some of the necessary
parent directories.
true if and only if the directory was created,
along with all necessar false
- If a security manager exists and its
method does not permit verification of the existence of the
named directory and all necessar or if
method does not permit the named directory and all necessary
parent directories to be created
public&boolean&renameTo(&dest)
Renames the file denoted by this abstract pathname.
Many aspects of the behavior of this method are inherently
platform-dependent: The rename operation might not be able to move a
file from one filesystem to another, it might not be atomic, and it
might not succeed if a file with the destination abstract pathname
already exists.
The return value should always be checked to make sure
that the rename operation was successful.
Note that the
class defines the
method to move or rename a file in a
platform independent manner.
Parameters:
dest - The new abstract pathname for the named file
true if and only if th
false otherwise
- If a security manager exists and its
method denies write access to either the old or new pathnames
- If parameter dest is null
setLastModified
public&boolean&setLastModified(long&time)
Sets the last-modified time of the file or directory named by this
abstract pathname.
All platforms support file-modification times to the nearest second,
but some provide more precision.
The argument will be truncated to fit
the supported precision.
If the operation succeeds and no intervening
operations on the file take place, then the next invocation of the
method will return the (possibly
truncated) time argument that was passed to this method.
Parameters:
time - The new last-modified time, measured in milliseconds since
the epoch (00:00:00 GMT, January 1, 1970)
true if and only if the
false otherwise
- If the argument is negative
- If a security manager exists and its
method denies write access to the named file
setReadOnly
public&boolean&setReadOnly()
Marks the file or directory named by this abstract pathname so that
only read operations are allowed. After invoking this method the file
or directory will not change until it is either deleted or marked
to allow write access. On some platforms it may be possible to start the
Java virtual machine with special privileges that allow it to modify
files that are marked read-only. Whether or not a read-only file or
directory may be deleted depends upon the underlying system.
true if and only if the
false otherwise
- If a security manager exists and its
method denies write access to the named file
setWritable
public&boolean&setWritable(boolean&writable,
boolean&ownerOnly)
Sets the owner's or everybody's write permission for this abstract
pathname. On some platforms it may be possible to start the Java virtual
machine with special privileges that allow it to modify files that
disallow write operations.
class defines methods that operate on
file attributes including file permissions. This may be used when finer
manipulation of file permissions is required.
Parameters:
writable - If true, sets the access permission to allow write
if false to disallow write operations
ownerOnly - If true, the write permission applies only to the
owner' otherwise, it applies to everybody.
the underlying file system can not distinguish the owner's write
permission from that of others, then the permission will apply to
everybody, regardless of this value.
true if and only if the operation succeeded. The
operation will fail if the user does not have permission to change
the access permissions of this abstract pathname.
- If a security manager exists and its
method denies write access to the named file
setWritable
public&boolean&setWritable(boolean&writable)
A convenience method to set the owner's write permission for this abstract
pathname. On some platforms it may be possible to start the Java virtual
machine with special privileges that allow it to modify files that
disallow write operations.
An invocation of this method of the form file.setWritable(arg)
behaves in exactly the same way as the invocation
file.setWritable(arg, true)
Parameters:
writable - If true, sets the access permission to allow write
if false to disallow write operations
true if and only if the operation succeeded.
operation will fail if the user does not have permission to
change the access permissions of this abstract pathname.
- If a security manager exists and its
method denies write access to the file
setReadable
public&boolean&setReadable(boolean&readable,
boolean&ownerOnly)
Sets the owner's or everybody's read permission for this abstract
pathname. On some platforms it may be possible to start the Java virtual
machine with special privileges that allow it to read files that are
marked as unreadable.
class defines methods that operate on
file attributes including file permissions. This may be used when finer
manipulation of file permissions is required.
Parameters:
readable - If true, sets the access permission to allow read
if false to disallow read operations
ownerOnly - If true, the read permission applies only to the
owner' otherwise, it applies to everybody.
the underlying file system can not distinguish the owner's read
permission from that of others, then the permission will apply to
everybody, regardless of this value.
true if and only if the operation succeeded.
operation will fail if the user does not have permission to
change the access permissions of this abstract pathname.
readable is false and the underlying
file system does not implement a read permission, then the
operation will fail.
- If a security manager exists and its
method denies write access to the file
setReadable
public&boolean&setReadable(boolean&readable)
A convenience method to set the owner's read permission for this abstract
pathname. On some platforms it may be possible to start the Java virtual
machine with special privileges that allow it to read files that that are
marked as unreadable.
An invocation of this method of the form file.setReadable(arg)
behaves in exactly the same way as the invocation
file.setReadable(arg, true)
Parameters:
readable - If true, sets the access permission to allow read
if false to disallow read operations
true if and only if the operation succeeded.
operation will fail if the user does not have permission to
change the access permissions of this abstract pathname.
readable is false and the underlying
file system does not implement a read permission, then the
operation will fail.
- If a security manager exists and its
method denies write access to the file
setExecutable
public&boolean&setExecutable(boolean&executable,
boolean&ownerOnly)
Sets the owner's or everybody's execute permission for this abstract
pathname. On some platforms it may be possible to start the Java virtual
machine with special privileges that allow it to execute files that are
not marked executable.
class defines methods that operate on
file attributes including file permissions. This may be used when finer
manipulation of file permissions is required.
Parameters:
executable - If true, sets the access permission to allow execute
if false to disallow execute operations
ownerOnly - If true, the execute permission applies only to the
owner' otherwise, it applies to everybody.
If the underlying file system can not distinguish the owner's
execute permission from that of others, then the permission will
apply to everybody, regardless of this value.
true if and only if the operation succeeded.
operation will fail if the user does not have permission to
change the access permissions of this abstract pathname.
executable is false and the underlying
file system does not implement an execute permission, then the
operation will fail.
- If a security manager exists and its
method denies write access to the file
setExecutable
public&boolean&setExecutable(boolean&executable)
A convenience method to set the owner's execute permission for this
abstract pathname. On some platforms it may be possible to start the Java
virtual machine with special privileges that allow it to execute files
that are not marked executable.
An invocation of this method of the form file.setExcutable(arg)
behaves in exactly the same way as the invocation
file.setExecutable(arg, true)
Parameters:
executable - If true, sets the access permission to allow execute
if false to disallow execute operations
true if and only if the operation succeeded.
operation will fail if the user does not have permission to
change the access permissions of this abstract pathname.
executable is false and the underlying
file system does not implement an execute permission, then the
operation will fail.
- If a security manager exists and its
method denies write access to the file
canExecute
public&boolean&canExecute()
Tests whether the application can execute the file denoted by this
abstract pathname. On some platforms it may be possible to start the
Java virtual machine with special privileges that allow it to execute
files that are not marked executable. Consequently this method may return
true even though the file does not have execute permissions.
true if and only if the abstract pathname exists
and the application is allowed to execute the file
- If a security manager exists and its
method denies execute access to the file
public static&[]&listRoots()
List the available filesystem roots.
A particular Java platform may support zero or more
hierarchically-organized file systems.
Each file system has a
root directory from which all other files in that file system
can be reached.
Windows platforms, for example, have a root directory
f UNIX platforms have a single root directory,
namely "/".
The set of available filesystem roots is affected
by various system-level operations such as the insertion or ejection of
removable media and the disconnecting or unmounting of physical or
virtual disk drives.
This method returns an array of File objects that denote the
root directories of the available filesystem roots.
It is guaranteed
that the canonical pathname of any file physically present on the local
machine will begin with one of the roots returned by this method.
The canonical pathname of a file that resides on some other machine
and is accessed via a remote-filesystem protocol such as SMB or NFS may
or may not begin with one of the roots returned by this method.
pathname of a remote file is syntactically indistinguishable from the
pathname of a local file then it will begin with one of the roots
returned by this method.
Thus, for example, File objects
denoting the root directories of the mapped network drives of a Windows
platform will be returned by this method, while File objects
containing UNC pathnames will not be returned by this method.
Unlike most methods in this class, this method does not throw
security exceptions.
If a security manager exists and its
method denies read access to a
particular root directory, then that directory will not appear in the
An array of File objects denoting the available
filesystem roots, or null if the set of roots could not
be determined.
The array will be empty if there are no
filesystem roots.
getTotalSpace
public&long&getTotalSpace()
Returns the size of the partition
abstract pathname.
The size, in bytes, of the partition or 0L if this
abstract pathname does not name a partition
- If a security manager has been installed and it denies
("getFileSystemAttributes")
method denies
read access to the file named by this abstract pathname
getFreeSpace
public&long&getFreeSpace()
Returns the number of unallocated bytes in the partition named by this abstract path name.
The returned number of unallocated bytes is a hint, but not
a guarantee, that it is possible to use most or any of these
The number of unallocated bytes is most likely to be
accurate immediately after this call.
It is likely to be made
inaccurate by any external I/O operations including those made
on the system outside of this virtual machine.
This method
makes no guarantee that write operations to this file system
will succeed.
The number of unallocated bytes on the partition or 0L
if the abstract pathname does not name a partition.
value will be less than or equal to the total file system size
returned by .
- If a security manager has been installed and it denies
("getFileSystemAttributes")
method denies
read access to the file named by this abstract pathname
getUsableSpace
public&long&getUsableSpace()
Returns the number of bytes available to this virtual machine on the
by this abstract pathname.
possible, this method checks for write permissions and other operating
system restrictions and will therefore usually provide a more accurate
estimate of how much new data can actually be written than .
The returned number of available bytes is a hint, but not a
guarantee, that it is possible to use most or any of these bytes.
number of unallocated bytes is most likely to be accurate immediately
after this call.
It is likely to be made inaccurate by any external
I/O operations including those made on the system outside of this
virtual machine.
This method makes no guarantee that write operations
to this file system will succeed.
The number of available bytes on the partition or 0L
if the abstract pathname does not name a partition.
systems where this information is not available, this method
will be equivalent to a call to .
- If a security manager has been installed and it denies
("getFileSystemAttributes")
method denies
read access to the file named by this abstract pathname
createTempFile
public static&&createTempFile(&prefix,
&directory)
Creates a new empty file in the specified directory, using the
given prefix and suffix strings to generate its name.
If this method
returns successfully then it is guaranteed that:
The file denoted by the returned abstract pathname did not exist
before this method was invoked, and
Neither this method nor any of its variants will return the same
abstract pathname again in the current invocation of the virtual
This method provides only part of a temporary-file facility.
To arrange
for a file created by this method to be deleted automatically, use the
The prefix argument must be at least three characters
It is recommended that the prefix be a short, meaningful string
such as "hjb" or "mail".
suffix argument may be null, in which case the
suffix ".tmp" will be used.
To create the new file, the prefix and the suffix may first be
adjusted to fit the limitations of the underlying platform.
prefix is too long then it will be truncated, but its first three
characters will always be preserved.
If the suffix is too long then it
too will be truncated, but if it begins with a period character
('.') then the period and the first three characters
following it will always be preserved.
Once these adjustments have been
made the name of the new file will be generated by concatenating the
prefix, five or more internally-generated characters, and the suffix.
If the directory argument is null then the
system-dependent default temporary-file directory will be used.
default temporary-file directory is specified by the system property
java.io.tmpdir.
On UNIX systems the default value of this
property is typically "/tmp" or "/var/tmp"; on
Microsoft Windows systems it is typically "C:\\WINNT\\TEMP".
A different
value may be given to this system property when the Java virtual machine
is invoked, but programmatic changes to this property are not guaranteed
to have any effect upon the temporary directory used by this method.
Parameters:
prefix - The prefix string to be used in generating the file's
must be at least three characters long
suffix - The suffix string to be used in generating the file's
may be null, in which case the
suffix ".tmp" will be used
directory - The directory in which the file is to be created, or
null if the default temporary-file
directory is to be used
An abstract pathname denoting a newly-created empty file
- If the prefix argument contains fewer than three
characters
- If a file could not be created
- If a security manager exists and its
method does not allow a file to be created
createTempFile
public static&&createTempFile(&prefix,
Creates an empty file in the default temporary-file directory, using
the given prefix and suffix to generate its name. Invoking this method
is equivalent to invoking .
method provides an alternative method to create an
empty file in the temporary-file directory. Files created by that method
may have more restrictive access permissions to files created by this
method and so may be more suited to security-sensitive applications.
Parameters:
prefix - The prefix string to be used in generating the file's
must be at least three characters long
suffix - The suffix string to be used in generating the file's
may be null, in which case the
suffix ".tmp" will be used
An abstract pathname denoting a newly-created empty file
- If the prefix argument contains fewer than three
characters
- If a file could not be created
- If a security manager exists and its
method does not allow a file to be created
public&int&compareTo(&pathname)
Compares two abstract pathnames lexicographically.
The ordering
defined by this method depends upon the underlying system.
systems, alphabetic case is significant in on Microsoft Windows
systems it is not.
Specified by:
&in interface&&&
Parameters:
pathname - The abstract pathname to be compared to this abstract
Zero if the argument is equal to this abstract pathname, a
value less than zero if this abstract pathname is
lexicographically less than the argument, or a value greater
than zero if this abstract pathname is lexicographically
greater than the argument
public&boolean&equals(&obj)
Tests this abstract pathname for equality with the given object.
Returns true if and only if the argument is not
null and is an abstract pathname that denotes the same file
or directory as this abstract pathname.
Whether or not two abstract
pathnames are equal depends upon the underlying system.
systems, alphabetic case is significant in on Microsoft Windows
systems it is not.
Overrides:
&in class&
Parameters:
obj - The object to be compared with this abstract pathname
true if and only if the
false otherwise
public&int&hashCode()
Computes a hash code for this abstract pathname.
Because equality of
abstract pathnames is inherently system-dependent, so is the computation
of their hash codes.
On UNIX systems, the hash code of an abstract
pathname is equal to the exclusive or of the hash code
of its pathname string and the decimal value
On Microsoft Windows systems, the hash
code is equal to the exclusive or of the hash code of
its pathname string converted to lower case and the decimal
value 1234321.
Locale is not taken into account on
lowercasing the pathname string.
Overrides:
&in class&
A hash code for this abstract pathname
public&&toString()
Returns the pathname string of this abstract pathname.
This is just the
string returned by the
Overrides:
&in class&
The string form of this abstract pathname
public&&toPath()
object constructed from the
this abstract path. The resulting Path is associated with the
The first invocation of this method works as if invoking it were
equivalent to evaluating the expression:
().(this.());
Subsequent invocations of this method return the same Path.
If this abstract pathname is the empty abstract pathname then this
method returns a Path that may be used to access the current
user directory.
a Path constructed from this abstract path
- if a Path object cannot be constructed from the abstract
path (see )
Java&&PlatformStandard&Ed.&8
For further API reference and developer documentation, see . That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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