public
class
File
extends Object
implements
Serializable,
Comparable<File>
java.lang.Object | |
↳ | java.io.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:
"/"
for the UNIX root
directory, or "\\\\"
for a Microsoft Windows UNC pathname, and
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
and separator
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.
separatorChar
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:
"/"
. Relative pathnames have no prefix. The abstract pathname
denoting the root directory has the prefix "/"
and an empty
name sequence.
":"
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.
On Android, the underlying filesystem encoding for filenames is always UTF-8.
Fields | |
---|---|
public
static
final
String |
pathSeparator
The system-dependent path-separator character, represented as a string for convenience. |
public
static
final
char |
pathSeparatorChar
The system-dependent path-separator character. |
public
static
final
String |
separator
The system-dependent default name-separator character, represented as a string for convenience. |
public
static
final
char |
separatorChar
The system-dependent default name-separator character. |
Public constructors | |
---|---|
File(String pathname)
Creates a new |
|
File(String parent, String child)
Creates a new |
|
File(File parent, String child)
Creates a new |
|
File(URI uri)
Creates a new File instance by converting the given file: URI into an abstract pathname. |
Public methods | |
---|---|
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, File directory)
Creates a new empty file in the specified directory, using the given prefix and suffix strings to generate its name. |
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. |
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 path of this file. |
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
|
File
|
getParentFile()
Returns the abstract pathname of this abstract pathname's parent,
or |
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(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. |
String[]
|
list()
Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname. |
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()
Returns the file system 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, boolean ownerOnly)
Sets the owner's or everybody's execute permission for this abstract pathname. |
boolean
|
setExecutable(boolean executable)
A convenience method to set the owner'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
|
setReadOnly()
Marks the file or directory named by this abstract pathname so that only read operations are allowed. |
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
|
setWritable(boolean writable, boolean ownerOnly)
Sets the owner's or everybody's write permission for this abstract pathname. |
boolean
|
setWritable(boolean writable)
A convenience method to set the owner's write permission for this abstract pathname. |
String
|
toString()
Returns the pathname string of this abstract pathname. |
URI
|
toURI()
Constructs a file: URI that represents this abstract pathname. |
URL
|
toURL()
This method was deprecated
in API level 9.
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
|
Inherited methods | |
---|---|
From
class
java.lang.Object
| |
From
interface
java.lang.Comparable
|
String pathSeparator
The system-dependent path-separator character, represented as a string
for convenience. This string contains a single character, namely
.
pathSeparatorChar
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
is ';'
.
See also:
String separator
The system-dependent default name-separator character, represented as a
string for convenience. This string contains a single character, namely
.
separatorChar
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 '\\'
.
See also:
File (String 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 |
String :
A pathname string |
Throws | |
---|---|
NullPointerException |
If the pathname argument is null
|
File (String parent, String child)
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 |
String :
The parent pathname string |
child |
String :
The child pathname string |
Throws | |
---|---|
NullPointerException |
If child is null
|
File (File parent, String child)
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 |
File :
The parent abstract pathname |
child |
String :
The child pathname string |
Throws | |
---|---|
NullPointerException |
If child is null
|
File (URI 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.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.toURI
()).equals( f.getAbsoluteFile
())
Parameters | |
---|---|
uri |
URI :
An absolute, hierarchical URI with a scheme equal to
"file", a non-empty path component, and undefined
authority, query, and fragment components |
Throws | |
---|---|
NullPointerException |
If uri is null |
IllegalArgumentException |
If the preconditions on the parameter do not hold |
boolean canExecute ()
Tests whether the application can execute the file denoted by this abstract pathname.
Returns | |
---|---|
boolean |
true if and only if the abstract pathname exists
and the application is allowed to execute the file |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies execute access to the file |
boolean canRead ()
Tests whether the application can read the file denoted by this abstract pathname.
Returns | |
---|---|
boolean |
true if and only if the file specified by this
abstract pathname exists and can be read by the
application; false otherwise |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies read access to the file
|
boolean canWrite ()
Tests whether the application can modify the file denoted by this abstract pathname.
Returns | |
---|---|
boolean |
true if and only if the file system actually
contains a file denoted by this abstract pathname and
the application is allowed to write to the file;
false otherwise. |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies write access to the file
|
int compareTo (File pathname)
Compares two abstract pathnames lexicographically. The ordering defined by this method depends upon the underlying system. On UNIX systems, alphabetic case is significant in comparing pathnames; on Microsoft Windows systems it is not.
Parameters | |
---|---|
pathname |
File :
The abstract pathname to be compared to this abstract
pathname |
Returns | |
---|---|
int |
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 |
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
FileLock
facility should be used instead.
Returns | |
---|---|
boolean |
true if the named file does not exist and was
successfully created; false if the named file
already exists |
Throws | |
---|---|
IOException |
If an I/O error occurred |
SecurityException |
If a security manager exists and its
method denies write access to the file |
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. If this method returns successfully then it is guaranteed that:
deleteOnExit()
method.
The prefix
argument must be at least three characters
long. It is recommended that the prefix be a short, meaningful string
such as "hjb"
or "mail"
. The
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. If the
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. The
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 |
String :
The prefix string to be used in generating the file's
name; must be at least three characters long |
suffix |
String :
The suffix string to be used in generating the file's
name; may be null , in which case the
suffix ".tmp" will be used |
directory |
File :
The directory in which the file is to be created, or
null if the default temporary-file
directory is to be used |
Returns | |
---|---|
File |
An abstract pathname denoting a newly-created empty file |
Throws | |
---|---|
IllegalArgumentException |
If the prefix argument contains fewer than three
characters |
IOException |
If a file could not be created |
SecurityException |
If a security manager exists and its
method does not allow a file to be created |
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. Invoking this method
is equivalent to invoking
.createTempFile(prefix, suffix, null)
Parameters | |
---|---|
prefix |
String :
The prefix string to be used in generating the file's
name; must be at least three characters long |
suffix |
String :
The suffix string to be used in generating the file's
name; may be null , in which case the
suffix ".tmp" will be used |
Returns | |
---|---|
File |
An abstract pathname denoting a newly-created empty file |
Throws | |
---|---|
IllegalArgumentException |
If the prefix argument contains fewer than three
characters |
IOException |
If a file could not be created |
SecurityException |
If a security manager exists and its
method does not allow a file to be created |
boolean delete ()
Deletes the file or directory denoted by this abstract pathname. If this pathname denotes a directory, then the directory must be empty in order to be deleted.
Returns | |
---|---|
boolean |
true if and only if the file or directory is
successfully deleted; false otherwise |
Throws | |
---|---|
SecurityException |
If a security manager exists and its method denies
delete access to the file
|
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 request. 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
FileLock
facility should be used instead.
Note that on Android, the application lifecycle does not include VM termination, so calling this method will not ensure that files are deleted. Instead, you should use the most appropriate out of:
finally
clause to manually invoke delete()
.
Throws | |
---|---|
SecurityException |
If a security manager exists and its method denies
delete access to the file |
See also:
boolean equals (Object 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. On UNIX
systems, alphabetic case is significant in comparing pathnames; on Microsoft Windows
systems it is not.
Parameters | |
---|---|
obj |
Object :
The object to be compared with this abstract pathname |
Returns | |
---|---|
boolean |
true if and only if the objects are the same;
false otherwise
|
boolean exists ()
Tests whether the file or directory denoted by this abstract pathname exists.
Returns | |
---|---|
boolean |
true if and only if the file or directory denoted
by this abstract pathname exists; false otherwise |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies read access to the file or directory
|
File getAbsoluteFile ()
Returns the absolute form of this abstract pathname. Equivalent to
new File(this.
.getAbsolutePath()
)
Returns | |
---|---|
File |
The absolute abstract pathname denoting the same file or directory as this abstract pathname |
Throws | |
---|---|
SecurityException |
If a required system property value cannot be accessed. |
String getAbsolutePath ()
Returns the absolute path of this file. An absolute path is a path that starts at a root
of the file system. On Android, there is only one root: /
.
A common use for absolute paths is when passing paths to a Process
as
command-line arguments, to remove the requirement implied by relative paths, that the
child must have the same working directory as its parent.
Returns | |
---|---|
String |
The absolute pathname string denoting the same file or directory as this abstract pathname |
See also:
File getCanonicalFile ()
Returns the canonical form of this abstract pathname. Equivalent to
new File(this.
.getCanonicalPath()
)
Returns | |
---|---|
File |
The canonical pathname string denoting the same file or directory as this abstract pathname |
Throws | |
---|---|
IOException |
If an I/O error occurs, which is possible because the construction of the canonical pathname may require filesystem queries |
SecurityException |
If a required system property value cannot be accessed, or
if a security manager exists and its method denies
read access to the file |
See also:
String 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
getAbsolutePath()
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 created. 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.
Returns | |
---|---|
String |
The canonical pathname string denoting the same file or directory as this abstract pathname |
Throws | |
---|---|
IOException |
If an I/O error occurs, which is possible because the construction of the canonical pathname may require filesystem queries |
SecurityException |
If a required system property value cannot be accessed, or
if a security manager exists and its method denies
read access to the file |
See also:
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 bytes. 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.
Returns | |
---|---|
long |
The number of unallocated bytes on the partition or 0L
if the abstract pathname does not name a partition. This
value will be less than or equal to the total file system size
returned by getTotalSpace() . |
Throws | |
---|---|
SecurityException |
If a security manager has been installed and it denies
RuntimePermission ("getFileSystemAttributes")
or its checkRead(String) method denies
read access to the file named by this abstract pathname |
String getName ()
Returns the name of the file or directory denoted by this abstract pathname. This is just the last name in the pathname's name sequence. If the pathname's name sequence is empty, then the empty string is returned.
Returns | |
---|---|
String |
The name of the file or directory denoted by this abstract pathname, or the empty string if this pathname's name sequence is empty |
String 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.
Returns | |
---|---|
String |
The pathname string of the parent directory named by this
abstract pathname, or null if this pathname
does not name a parent
|
File 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.
Returns | |
---|---|
File |
The abstract pathname of the parent directory named by this
abstract pathname, or null if this pathname
does not name a parent |
String getPath ()
Converts this abstract pathname into a pathname string. The resulting
string uses the default name-separator character
to
separate the names in the name sequence.
Returns | |
---|---|
String |
The string form of this abstract pathname |
long getTotalSpace ()
Returns the size of the partition named by this abstract pathname.
Returns | |
---|---|
long |
The size, in bytes, of the partition or 0L if this abstract pathname does not name a partition |
Throws | |
---|---|
SecurityException |
If a security manager has been installed and it denies
RuntimePermission ("getFileSystemAttributes")
or its checkRead(String) method denies
read access to the file 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. When
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 getFreeSpace()
.
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. 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.
On Android (and other Unix-based systems), this method returns the number of free bytes
available to non-root users, regardless of whether you're actually running as root,
and regardless of any quota or other restrictions that might apply to the user.
(The getFreeSpace
method returns the number of bytes potentially available to root.)
Returns | |
---|---|
long |
The number of available bytes on the partition or 0L
if the abstract pathname does not name a partition. On
systems where this information is not available, this method
will be equivalent to a call to getFreeSpace() . |
Throws | |
---|---|
SecurityException |
If a security manager has been installed and it denies
RuntimePermission ("getFileSystemAttributes")
or its checkRead(String) method denies
read access to the file named by this abstract pathname |
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
1234321
. 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.
Returns | |
---|---|
int |
A hash code for this abstract pathname |
boolean isAbsolute ()
Tests whether this abstract pathname is absolute. The definition of absolute pathname is system dependent. On Android, absolute paths start with the character '/'.
Returns | |
---|---|
boolean |
true if this abstract pathname is absolute,
false otherwise
|
boolean isDirectory ()
Tests whether the file denoted by this abstract pathname is a directory.
Returns | |
---|---|
boolean |
true if and only if the file denoted by this
abstract pathname exists and is a directory;
false otherwise |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies read access to the file
|
boolean isFile ()
Tests whether the file denoted by this abstract pathname is a normal file. 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.
Returns | |
---|---|
boolean |
true if and only if the file denoted by this
abstract pathname exists and is a normal file;
false otherwise |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies read access to the file
|
boolean isHidden ()
Tests whether the file named by this abstract pathname is a hidden
file. The exact definition of hidden is system-dependent. On
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.
Returns | |
---|---|
boolean |
true if and only if the file denoted by this
abstract pathname is hidden according to the conventions of the
underlying platform |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies read access to the file |
long lastModified ()
Returns the time that the file denoted by this abstract pathname was last modified.
Returns | |
---|---|
long |
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 |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies read access to the file
|
long length ()
Returns the length of the file denoted by this abstract pathname. The return value is unspecified if this pathname denotes a directory.
Returns | |
---|---|
long |
The length, in bytes, of the file denoted by this abstract
pathname, or 0L if the file does not exist. Some
operating systems may return 0L for pathnames
denoting system-dependent entities such as devices or pipes. |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies read access to the file
|
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. The behavior of this method is the same as that of the
list()
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 FilenameFilter.accept(File, String)
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 |
FilenameFilter :
A filename filter |
Returns | |
---|---|
String[] |
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. |
Throws | |
---|---|
SecurityException |
If a security manager exists and its checkRead(String) method denies read access to
the directory
|
String[] 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. Names
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 in any specific order; they are not, in particular, guaranteed to appear in alphabetical order.
Returns | |
---|---|
String[] |
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. |
Throws | |
---|---|
SecurityException |
If a security manager exists and its checkRead(String) method denies read access to
the directory
|
File[] 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. Pathnames
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 File(File, String)
constructor. Therefore if this
pathname is absolute then each resulting pathname is absolute; if this
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 in any specific order; they are not, in particular, guaranteed to appear in alphabetical order.
Returns | |
---|---|
File[] |
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. Returns
null if this abstract pathname does not denote a
directory, or if an I/O error occurs. |
Throws | |
---|---|
SecurityException |
If a security manager exists and its checkRead(String) method denies read access to
the directory |
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. The behavior of this method is the same
as that of the listFiles()
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
the FileFilter.accept(File)
method of the
filter is invoked on the pathname.
Parameters | |
---|---|
filter |
FileFilter :
A file filter |
Returns | |
---|---|
File[] |
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. Returns
null if this abstract pathname does not denote a
directory, or if an I/O error occurs. |
Throws | |
---|---|
SecurityException |
If a security manager exists and its checkRead(String) method denies read access to
the directory |
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. The behavior of this method is the same
as that of the listFiles()
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
the FilenameFilter.accept(File, String)
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 |
FilenameFilter :
A filename filter |
Returns | |
---|---|
File[] |
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. Returns
null if this abstract pathname does not denote a
directory, or if an I/O error occurs. |
Throws | |
---|---|
SecurityException |
If a security manager exists and its checkRead(String) method denies read access to
the directory |
File[] listRoots ()
Returns the file system roots. On Android and other Unix systems, there is
a single root, /
.
Returns | |
---|---|
File[] |
boolean mkdir ()
Creates the directory named by this abstract pathname.
Returns | |
---|---|
boolean |
true if and only if the directory was
created; false otherwise |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method does not permit the named directory to be created
|
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.
Returns | |
---|---|
boolean |
true if and only if the directory was created,
along with all necessary parent directories; false
otherwise |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method does not permit verification of the existence of the
named directory and all necessary parent directories; or if
the
method does not permit the named directory and all necessary
parent directories to be created
|
boolean renameTo (File dest)
Renames the file denoted by this abstract pathname.
Many failures are possible. Some of the more likely failures include:
The return value should always be checked to make sure that the rename operation was successful.
Parameters | |
---|---|
dest |
File :
The new abstract pathname for the named file |
Returns | |
---|---|
boolean |
true if and only if the renaming succeeded;
false otherwise |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies write access to either the old or new pathnames |
NullPointerException |
If parameter dest is null
|
boolean setExecutable (boolean executable, boolean ownerOnly)
Sets the owner's or everybody's execute permission for this abstract pathname.
Parameters | |
---|---|
executable |
boolean :
If true , sets the access permission to allow execute
operations; if false to disallow execute operations |
ownerOnly |
boolean :
If true , the execute permission applies only to the
owner's execute permission; 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. |
Returns | |
---|---|
boolean |
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
executable is false and the underlying
file system does not implement an execute permission, then the
operation will fail. |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies write access to the file |
boolean setExecutable (boolean executable)
A convenience method to set the owner's execute permission for this abstract pathname.
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 |
boolean :
If true , sets the access permission to allow execute
operations; if false to disallow execute operations |
Returns | |
---|---|
boolean |
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
executable is false and the underlying
file system does not implement an excute permission, then the
operation will fail. |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies write access to the file |
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) lastModified()
time
argument that was passed to this method.
Parameters | |
---|---|
time |
long :
The new last-modified time, measured in milliseconds since
the epoch (00:00:00 GMT, January 1, 1970) |
Returns | |
---|---|
boolean |
true if and only if the operation succeeded;
false otherwise |
Throws | |
---|---|
IllegalArgumentException |
If the argument is negative |
SecurityException |
If a security manager exists and its
method denies write access to the named file |
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 is guaranteed not to change until it is either deleted or marked to allow write access. Whether or not a read-only file or directory may be deleted depends upon the underlying system.
Returns | |
---|---|
boolean |
true if and only if the operation succeeded;
false otherwise |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies write access to the named file |
boolean setReadable (boolean readable)
A convenience method to set the owner's read permission for this abstract pathname.
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 |
boolean :
If true , sets the access permission to allow read
operations; if false to disallow read operations |
Returns | |
---|---|
boolean |
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
readable is false and the underlying
file system does not implement a read permission, then the
operation will fail. |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies write access to the file |
boolean setReadable (boolean readable, boolean ownerOnly)
Sets the owner's or everybody's read permission for this abstract pathname.
Parameters | |
---|---|
readable |
boolean :
If true , sets the access permission to allow read
operations; if false to disallow read operations |
ownerOnly |
boolean :
If true , the read permission applies only to the
owner's read permission; otherwise, it applies to everybody. If
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. |
Returns | |
---|---|
boolean |
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
readable is false and the underlying
file system does not implement a read permission, then the
operation will fail. |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies write access to the file |
boolean setWritable (boolean writable, boolean ownerOnly)
Sets the owner's or everybody's write permission for this abstract pathname.
Parameters | |
---|---|
writable |
boolean :
If true , sets the access permission to allow write
operations; if false to disallow write operations |
ownerOnly |
boolean :
If true , the write permission applies only to the
owner's write permission; otherwise, it applies to everybody. If
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. |
Returns | |
---|---|
boolean |
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. |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies write access to the named file |
boolean setWritable (boolean writable)
A convenience method to set the owner's write permission for this abstract pathname.
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 |
boolean :
If true , sets the access permission to allow write
operations; if false to disallow write operations |
Returns | |
---|---|
boolean |
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. |
Throws | |
---|---|
SecurityException |
If a security manager exists and its
method denies write access to the file |
String toString ()
Returns the pathname string of this abstract pathname. This is just the
string returned by the
method.getPath()
Returns | |
---|---|
String |
The string form of this abstract pathname |
URI 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
newso 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.File
( f.toURI()).equals( f.getAbsoluteFile
())
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
.
Returns | |
---|---|
URI |
An absolute, hierarchical URI with a scheme equal to "file", a path representing this abstract pathname, and undefined authority, query, and fragment components |
Throws | |
---|---|
SecurityException |
If a required system property value cannot be accessed. |
See also:
URL toURL ()
This method was deprecated
in API level 9.
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.
Converts this abstract pathname into a file:
URL. The
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.
Returns | |
---|---|
URL |
A URL object representing the equivalent file URL |
Throws | |
---|---|
MalformedURLException |
If the path cannot be parsed as a URL |