Class File
- All Implemented Interfaces:
Serializable
,Comparable<File>
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:
- 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 conversion of a pathname string to or from an abstract pathname is
inherently system-dependent. When an abstract pathname is converted into a
pathname string, each name is separated from the next by a single copy of
the default separator character. The default name-separator
character is defined by the system property file.separator
, and
is made available in the public static fields separator
and separatorChar
of this class.
When a pathname string is converted into an abstract pathname, the names
within it may be separated by the default name-separator character or by any
other name-separator character that is supported by the underlying system.
A pathname, whether abstract or in string form, may be either
absolute or relative. An absolute pathname is complete in
that no other information is required in order to locate the file that it
denotes. A relative pathname, in contrast, must be interpreted in terms of
information taken from some other pathname. By default the classes in the
java.io
package always resolve relative pathnames against the
current user directory. This directory is named by the system property
user.dir
, and is typically the directory in which the Java
virtual machine was invoked.
Unless otherwise noted, symbolic links
are automatically redirected to the target of the link, whether they
are provided by a pathname string or via a File
object.
The parent of an abstract pathname may be obtained by invoking
the getParent()
method of this class and consists of the pathname's
prefix and each name in the pathname's name sequence except for the last.
Each directory's absolute pathname is an ancestor of any File
object with an absolute abstract pathname which begins with the directory's
absolute pathname. For example, the directory denoted by the abstract
pathname "/usr"
is an ancestor of the directory denoted by the
pathname "/usr/local/bin"
.
The prefix concept is used to handle root directories on UNIX platforms, and drive specifiers, root directories and UNC pathnames on Microsoft Windows platforms, as follows:
- For UNIX platforms, the prefix of an absolute pathname is always
"/"
. Relative pathnames have no prefix. The abstract pathname denoting the root directory has the prefix"/"
and an empty name sequence. - For Microsoft Windows platforms, the prefix of a pathname that contains a drive
specifier consists of the drive letter followed by
":"
and possibly followed by"\\"
if the pathname is absolute. The prefix of a UNC pathname is"\\\\"
; the hostname and the share name are the first two names in the name sequence. A relative pathname that does not specify a drive has no prefix.
Instances of this class may or may not denote an actual file-system object such as a file or a directory. If it does denote such an object then that object resides in a partition. A partition is an operating system-specific portion of storage for a file system. A single storage device (e.g. a physical disk-drive, flash memory, CD-ROM) may contain multiple partitions. The object, if any, will reside on the partition named by some ancestor of the absolute form of this pathname.
A file system may implement restrictions to certain operations on the actual file-system object, such as reading, writing, and executing. These restrictions are collectively known as access permissions. The file system may have multiple sets of access permissions on a single object. For example, one set may apply to the object's owner, and another may apply to all other users. The access permissions on an object may cause some methods in this class to fail.
Instances of the File
class are immutable; that is, once
created, the abstract pathname represented by a File
object
will never change.
Interoperability with java.nio.file
package
The java.nio.file
package defines interfaces and classes for the Java virtual machine to access
files, file attributes, and file systems. This API may be used to overcome
many of the limitations of the java.io.File
class.
The toPath
method may be used to obtain a Path
that uses the abstract path represented by a File
object to
locate a file. The resulting Path
may be used with the Files
class to provide more efficient and extensive access to
additional file operations, file attributes, and I/O exceptions to help
diagnose errors when an operation on a file fails.
- Since:
- 1.0
- See Also:
-
Field Summary
Modifier and TypeFieldDescriptionstatic final String
The system-dependent path-separator character, represented as a string for convenience.static final char
The system-dependent path-separator character.static final String
The system-dependent default name-separator character, represented as a string for convenience.static final char
The system-dependent default name-separator character. -
Constructor Summary
ConstructorDescriptionCreates a newFile
instance from a parent abstract pathname and a child pathname string.Creates a newFile
instance by converting the given pathname string into an abstract pathname.Creates a newFile
instance from a parent pathname string and a child pathname string.Creates a newFile
instance by converting the givenfile:
URI into an abstract pathname. -
Method Summary
Modifier and TypeMethodDescriptionboolean
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
Compares two abstract pathnames lexicographically.boolean
Atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist.static File
createTempFile
(String prefix, String suffix) Creates an empty file in the default temporary-file directory, using the given prefix and suffix to generate its name.static File
createTempFile
(String prefix, String suffix, File directory) Creates a new empty file in the specified directory, using the given prefix and suffix strings to generate its name.boolean
delete()
Deletes the file or directory denoted by this abstract pathname.void
Requests that the file or directory denoted by this abstract pathname be deleted when the virtual machine terminates.boolean
Tests this abstract pathname for equality with the given object.boolean
exists()
Tests whether the file or directory denoted by this abstract pathname exists.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.long
Returns the number of unallocated bytes in the partition named by this abstract path name.getName()
Returns the name of the file or directory denoted by this abstract pathname.Returns the pathname string of this abstract pathname's parent, ornull
if this pathname does not name a parent directory.Returns the abstract pathname of this abstract pathname's parent, ornull
if this pathname does not name a parent directory.getPath()
Converts this abstract pathname into a pathname string.long
Returns the size of the partition named by this abstract pathname.long
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
Tests whether this abstract pathname is absolute.boolean
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
Returns the time that the file denoted by this abstract pathname was last modified.long
length()
Returns the length of the file denoted by this abstract pathname.String[]
list()
Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname.String[]
list
(FilenameFilter filter) Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter.File[]
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[]
List the available filesystem roots.boolean
mkdir()
Creates the directory named by this abstract pathname.boolean
mkdirs()
Creates the directory named by this abstract pathname, including any necessary but nonexistent parent directories.boolean
Renames the file denoted by this abstract pathname.boolean
setExecutable
(boolean executable) A convenience method to set the owner's execute permission for this abstract pathname.boolean
setExecutable
(boolean executable, boolean ownerOnly) Sets the owner's or everybody's execute permission for this abstract pathname.boolean
setLastModified
(long time) Sets the last-modified time of the file or directory named by this abstract pathname.boolean
setReadable
(boolean readable) A convenience method to set the owner's read permission for this abstract pathname.boolean
setReadable
(boolean readable, boolean ownerOnly) Sets the owner's or everybody's read permission for this abstract pathname.boolean
Marks the file or directory named by this abstract pathname so that only read operations are allowed.boolean
setWritable
(boolean writable) A convenience method to set the owner's write permission for this abstract pathname.boolean
setWritable
(boolean writable, boolean ownerOnly) Sets the owner's or everybody's write permission for this abstract pathname.toPath()
Returns ajava.nio.file.Path
object constructed from this abstract path.toString()
Returns the pathname string of this abstract pathname.toURI()
Constructs afile:
URI that represents this abstract pathname.toURL()
Deprecated.This method does not automatically escape characters that are illegal in URLs.
-
Field Details
-
separatorChar
public static final char separatorCharThe system-dependent default name-separator character. This field is initialized to contain the first character of the value of the system propertyfile.separator
. On UNIX systems the value of this field is'/'
; on Microsoft Windows systems it is'\\'
.- See Also:
-
separator
The system-dependent default name-separator character, represented as a string for convenience. This string contains a single character, namelyseparatorChar
. -
pathSeparatorChar
public static final char pathSeparatorCharThe system-dependent path-separator character. This field is initialized to contain the first character of the value of the system propertypath.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:
-
pathSeparator
The system-dependent path-separator character, represented as a string for convenience. This string contains a single character, namelypathSeparatorChar
.
-
-
Constructor Details
-
File
Creates a newFile
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- Throws:
NullPointerException
- If thepathname
argument isnull
-
File
Creates a newFile
instance from a parent pathname string and a child pathname string.If
parent
isnull
then the newFile
instance is created as if by invoking the single-argumentFile
constructor on the givenchild
pathname string.Otherwise the
parent
pathname string is taken to denote a directory, and thechild
pathname string is taken to denote either a directory or a file. If thechild
pathname string is absolute then it is converted into a relative pathname in a system-dependent way. Ifparent
is the empty string then the newFile
instance is created by convertingchild
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 stringchild
- The child pathname string- Throws:
NullPointerException
- Ifchild
isnull
-
File
Creates a newFile
instance from a parent abstract pathname and a child pathname string.If
parent
isnull
then the newFile
instance is created as if by invoking the single-argumentFile
constructor on the givenchild
pathname string.Otherwise the
parent
abstract pathname is taken to denote a directory, and thechild
pathname string is taken to denote either a directory or a file. If thechild
pathname string is absolute then it is converted into a relative pathname in a system-dependent way. Ifparent
is the empty abstract pathname then the newFile
instance is created by convertingchild
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 pathnamechild
- The child pathname string- Throws:
NullPointerException
- Ifchild
isnull
-
File
Creates a newFile
instance by converting the givenfile:
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
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 anew File(
f.
ftoURI
()).equals(.
getAbsoluteFile
())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- Throws:
NullPointerException
- Ifuri
isnull
IllegalArgumentException
- If the preconditions on the parameter do not hold- Since:
- 1.4
- See Also:
-
-
Method Details
-
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:
- The name of the file or directory denoted by this abstract pathname, or the empty string if this pathname's name sequence is empty
-
getParent
Returns the pathname string of this abstract pathname's parent, ornull
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:
- The pathname string of the parent directory named by this
abstract pathname, or
null
if this pathname does not name a parent
-
getParentFile
Returns the abstract pathname of this abstract pathname's parent, ornull
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:
- The abstract pathname of the parent directory named by this
abstract pathname, or
null
if this pathname does not name a parent - Since:
- 1.2
-
getPath
Converts this abstract pathname into a pathname string. The resulting string uses thedefault name-separator character
to separate the names in the name sequence.- Returns:
- 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"\\\\"
.- Returns:
true
if this abstract pathname is absolute,false
otherwise
-
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
getPath()
method. If this abstract pathname is the empty abstract pathname then the pathname string of the current user directory, which is named by the system propertyuser.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 any; if not, it is resolved against the current user directory.- Returns:
- The absolute pathname string denoting the same file or directory as this abstract pathname
- See Also:
-
getAbsoluteFile
Returns the absolute form of this abstract pathname. Equivalent tonew File(this.
.getAbsolutePath()
)- Returns:
- The absolute abstract pathname denoting the same file or directory as this abstract pathname
- Since:
- 1.2
-
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:
- 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- Since:
- 1.1
- See Also:
-
getCanonicalFile
Returns the canonical form of this abstract pathname. Equivalent tonew File(this.
.getCanonicalPath()
)- Returns:
- 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- Since:
- 1.2
- See Also:
-
toURL
Deprecated.Converts this abstract pathname into afile:
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:
- A URL object representing the equivalent file URL
- Throws:
MalformedURLException
- If the path cannot be parsed as a URL- Since:
- 1.2
- See Also:
-
toURI
Constructs afile:
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
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 anew
fFile
(.toURI()).equals(
f.
getAbsoluteFile
())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 asnull
. ThePath
class defines thetoUri
method to encode the server name in the authority component of the resultingURI
. ThetoPath
method may be used to obtain aPath
representing this abstract pathname.- Returns:
- An absolute, hierarchical URI with a scheme equal to
"file"
, a path representing this abstract pathname, and undefined authority, query, and fragment components - Since:
- 1.4
- See Also:
-
canRead
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 returntrue
even though the file does not have read permissions.- Returns:
true
if and only if the file specified by this abstract pathname exists and can be read by the application;false
otherwise
-
canWrite
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 returntrue
even though the file is marked read-only.- Returns:
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.
-
exists
public boolean exists()Tests whether the file or directory denoted by this abstract pathname exists.- Returns:
true
if and only if the file or directory denoted by this abstract pathname exists;false
otherwise
-
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
Files.readAttributes
method may be used.- Returns:
true
if and only if the file denoted by this abstract pathname exists and is a directory;false
otherwise
-
isFile
public 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.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
Files.readAttributes
method may be used.- Returns:
true
if and only if the file denoted by this abstract pathname exists and is a normal file;false
otherwise
-
isHidden
public 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.- Implementation Note:
- If the file is a symbolic link, then on UNIX system it is considered to be hidden if the name of the link itself, not that of its target, begins with a period character. On Windows systems, a symbolic link is considered hidden if its target is so marked in the filesystem.
- Returns:
true
if and only if the file denoted by this abstract pathname is hidden according to the conventions of the underlying platform- Since:
- 1.2
-
lastModified
public long lastModified()Returns the time that the file denoted by this abstract pathname was last modified.- API Note:
- While the unit of time of the return value is milliseconds, the
granularity of the value depends on the underlying file system and may
be larger. For example, some file systems use time stamps in units of
seconds.
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 theFiles.readAttributes
method may be used. If however only the time of last modification is required, then theFiles.getLastModifiedTime
method may be used instead. - Returns:
- A
long
value representing the time the file was last modified, measured in milliseconds since the epoch (00:00:00 GMT, January 1, 1970), or0L
if the file does not exist or if an I/O error occurs. The value may be negative indicating the number of milliseconds before the epoch
-
length
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 theFiles.readAttributes
method may be used.- Returns:
- The length, in bytes, of the file denoted by this abstract
pathname, or
0L
if the file does not exist. Some operating systems may return0L
for pathnames denoting system-dependent entities such as devices or pipes.
-
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:
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- Since:
- 1.2
-
delete
public 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. If this pathname denotes a symbolic link, then the link itself, not its target, will be deleted.Note that the
Files
class defines thedelete
method to throw anIOException
when a file cannot be deleted. This is useful for error reporting and to diagnose why a file cannot be deleted.- Returns:
true
if and only if the file or directory is successfully deleted;false
otherwise
-
deleteOnExit
public void deleteOnExit()Requests that the file or directory denoted by this abstract pathname be deleted when the virtual machine terminates. If this pathname denotes a symbolic link, then the link itself, not its target, will be deleted. 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.- Since:
- 1.2
- See Also:
-
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.
Note that the
Files
class defines thenewDirectoryStream
method 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, and may be more responsive when working with remote directories.- Returns:
- 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.
-
list
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 thelist()
method, except that the strings in the returned array must satisfy the filter. If the givenfilter
isnull
then all names are accepted. Otherwise, a name satisfies the filter if and only if the valuetrue
results when theFilenameFilter.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
- A filename filter- Returns:
- 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. Returnsnull
if this abstract pathname does not denote a directory, or if an I/O error occurs. - See Also:
-
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 ofFile
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 theFile(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.
Note that the
Files
class defines thenewDirectoryStream
method 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.- Returns:
- 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. - Since:
- 1.2
-
listFiles
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 thelistFiles()
method, except that the pathnames in the returned array must satisfy the filter. If the givenfilter
isnull
then all pathnames are accepted. Otherwise, a pathname satisfies the filter if and only if the valuetrue
results when theFilenameFilter.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
- A filename filter- Returns:
- 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. - Since:
- 1.2
- See Also:
-
listFiles
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 thelistFiles()
method, except that the pathnames in the returned array must satisfy the filter. If the givenfilter
isnull
then all pathnames are accepted. Otherwise, a pathname satisfies the filter if and only if the valuetrue
results when theFileFilter.accept(File)
method of the filter is invoked on the pathname.- Parameters:
filter
- A file filter- Returns:
- 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. - Since:
- 1.2
- See Also:
-
mkdir
public boolean mkdir()Creates the directory named by this abstract pathname.- Returns:
true
if and only if the directory was created;false
otherwise
-
mkdirs
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.- Returns:
true
if and only if the directory was created, along with all necessary parent directories;false
otherwise
-
renameTo
Renames the file denoted by this abstract pathname. If this pathname denotes a symbolic link, then the link itself, not its target, will be renamed.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. As instances of
File
are immutable, this File object is not changed to name the destination file or directory.Note that the
Files
class defines themove
method to move or rename a file in a platform independent manner.- Parameters:
dest
- The new abstract pathname for the named file- Returns:
true
if and only if the renaming succeeded;false
otherwise- Throws:
NullPointerException
- If parameterdest
isnull
-
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
lastModified()
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)- Returns:
true
if and only if the operation succeeded;false
otherwise- Throws:
IllegalArgumentException
- If the argument is negative- Since:
- 1.2
-
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.- Returns:
true
if and only if the operation succeeded;false
otherwise- Since:
- 1.2
-
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.The
Files
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
- Iftrue
, sets the access permission to allow write operations; iffalse
to disallow write operationsownerOnly
- Iftrue
, 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:
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.- Since:
- 1.6
-
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 invocationfile.setWritable(arg, true)
- Parameters:
writable
- Iftrue
, sets the access permission to allow write operations; iffalse
to disallow write operations- Returns:
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.- Since:
- 1.6
-
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.The
Files
class defines methods that operate on file attributes including file permissions. This may be used when finer manipulation of file permissions is required.If the platform supports setting a file's read permission, but the user does not have permission to change the access permissions of this abstract pathname, then the operation will fail. If the platform does not support setting a file's read permission, this method does nothing and returns the value of the
readable
parameter.- Parameters:
readable
- Iftrue
, sets the access permission to allow read operations; iffalse
to disallow read operationsownerOnly
- Iftrue
, 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:
true
if the operation succeeds,false
if it fails, or the value of thereadable
parameter if setting the read permission is not supported.- Since:
- 1.6
-
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 are marked as unreadable.An invocation of this method of the form
file.setReadable(arg)
behaves in exactly the same way as the invocationfile.setReadable(arg, true)
If the platform supports setting a file's read permission, but the user does not have permission to change the access permissions of this abstract pathname, then the operation will fail. If the platform does not support setting a file's read permission, this method does nothing and returns the value of the
readable
parameter.- Parameters:
readable
- Iftrue
, sets the access permission to allow read operations; iffalse
to disallow read operations- Returns:
true
if the operation succeeds,false
if it fails, or the value of thereadable
parameter if setting the read permission is not supported.- Since:
- 1.6
-
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.The
Files
class defines methods that operate on file attributes including file permissions. This may be used when finer manipulation of file permissions is required.If the platform supports setting a file's execute permission, but the user does not have permission to change the access permissions of this abstract pathname, then the operation will fail. If the platform does not support setting a file's execute permission, this method does nothing and returns the value of the
executable
parameter.- Parameters:
executable
- Iftrue
, sets the access permission to allow execute operations; iffalse
to disallow execute operationsownerOnly
- Iftrue
, 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:
true
if the operation succeeds,false
if it fails, or the value of theexecutable
parameter if setting the execute permission is not supported.- Since:
- 1.6
-
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 invocationfile.setExecutable(arg, true)
If the platform supports setting a file's execute permission, but the user does not have permission to change the access permissions of this abstract pathname, then the operation will fail. If the platform does not support setting a file's execute permission, this method does nothing and returns the value of the
executable
parameter.- Parameters:
executable
- Iftrue
, sets the access permission to allow execute operations; iffalse
to disallow execute operations- Returns:
true
if the operation succeeds,false
if it fails, or the value of theexecutable
parameter if setting the execute permission is not supported.- Since:
- 1.6
-
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 returntrue
even though the file does not have execute permissions.- Returns:
true
if and only if the abstract pathname exists and the application is allowed to execute the file- Since:
- 1.6
-
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.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. There is no guarantee that a root directory can be accessed.- Implementation Note:
- Windows platforms, for example, have a root directory
for each active drive; UNIX platforms have a single root directory,
namely
"/"
. The set of filesystem roots is affected by various system-level operations such as the disconnecting or unmounting of physical or virtual disk drives.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. If the 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, whileFile
objects containing UNC pathnames will not be returned by this method. - Returns:
- An array of
File
objects denoting the available filesystem roots, ornull
if the set of roots could not be determined. The array will be empty if there are no filesystem roots. - Since:
- 1.2
- See Also:
-
getTotalSpace
public long getTotalSpace()Returns the size of the partition named by this abstract pathname. If the total number of bytes in the partition is greater thanLong.MAX_VALUE
, thenLong.MAX_VALUE
will be returned.- Returns:
- The size, in bytes, of the partition or
0L
if this abstract pathname does not name a partition or if the size cannot be obtained - Since:
- 1.6
- See Also:
-
getFreeSpace
public long getFreeSpace()Returns the number of unallocated bytes in the partition named by this abstract path name. If the number of unallocated bytes in the partition is greater thanLong.MAX_VALUE
, thenLong.MAX_VALUE
will be returned.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:
- The number of unallocated bytes on the partition or
0L
if the abstract pathname does not name a partition or if this number cannot be obtained. This value will be less than or equal to the total file system size returned bygetTotalSpace()
. - Since:
- 1.6
- See Also:
-
getUsableSpace
public long getUsableSpace()Returns the number of bytes available to this virtual machine on the partition named by this abstract pathname. If the number of available bytes in the partition is greater thanLong.MAX_VALUE
, thenLong.MAX_VALUE
will be returned. 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 thangetFreeSpace()
.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 available 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:
- The number of available bytes on the partition or
0L
if the abstract pathname does not name a partition or if this number cannot be obtained. On systems where this information is not available, this method will be equivalent to a call togetFreeSpace()
. - Since:
- 1.6
- See Also:
-
createTempFile
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 machine.
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"
. Thesuffix
argument may benull
, 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 a file with the generated name cannot be created by the underlying platform, then an
IOException
will be thrown. This could occur for example if the supplied prefix or suffix contains one or more characters not supported by the underlying file system.If the
directory
argument isnull
then the system-dependent default temporary-file directory will be used. The default temporary-file directory is specified by the system propertyjava.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.If the
directory
argument is notnull
and its abstract pathname is valid and denotes an existing, writable directory, then the file will be created in that directory. Otherwise the file will not be created and anIOException
will be thrown. Under no circumstances will a directory be created at the location specified by thedirectory
argument.- Parameters:
prefix
- The prefix string to be used in generating the file's name; must be at least three characters longsuffix
- The suffix string to be used in generating the file's name; may benull
, in which case the suffix".tmp"
will be useddirectory
- The directory in which the file is to be created, ornull
if the default temporary-file directory is to be used- Returns:
- An abstract pathname denoting a newly-created empty file
- Throws:
IllegalArgumentException
- If theprefix
argument contains fewer than three charactersIOException
- If a file could not be created- Since:
- 1.2
-
createTempFile
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 invokingcreateTempFile(prefix, suffix, null)
.The
Files.createTempFile
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 name; must be at least three characters longsuffix
- The suffix string to be used in generating the file's name; may benull
, in which case the suffix".tmp"
will be used- Returns:
- An abstract pathname denoting a newly-created empty file
- Throws:
IllegalArgumentException
- If theprefix
argument contains fewer than three charactersIOException
- If a file could not be created- Since:
- 1.2
- See Also:
-
compareTo
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.- Specified by:
compareTo
in interfaceComparable<File>
- Parameters:
pathname
- The abstract pathname to be compared to this abstract pathname- Returns:
- 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
- Since:
- 1.2
-
equals
Tests this abstract pathname for equality with the given object. Returnstrue
if and only if the argument is notnull
and is an abstract pathname that is the same as this abstract pathname. Whether or not two abstract pathnames are equal depends upon the underlying operating system. On UNIX systems, alphabetic case is significant in comparing pathnames; on Microsoft Windows systems it is not.- Overrides:
equals
in classObject
- API Note:
- This method only tests whether the abstract pathnames are equal; it does not access the file system and the file is not required to exist.
- Parameters:
obj
- The object to be compared with this abstract pathname- Returns:
true
if and only if the objects are the same;false
otherwise- See Also:
-
hashCode
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 value1234321
. 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 value1234321
. Locale is not taken into account on lowercasing the pathname string. -
toString
-
toPath
Returns ajava.nio.file.Path
object constructed from this abstract path. The resultingPath
is associated with thedefault-filesystem
.The first invocation of this method works as if invoking it were equivalent to evaluating the expression:
FileSystems.getDefault().
getPath
(this.getPath());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.- Returns:
- a
Path
constructed from this abstract path - Throws:
InvalidPathException
- if aPath
object cannot be constructed from the abstract path (seeFileSystem.getPath
)- Since:
- 1.7
- See Also:
-