Class File
- java.lang.Object
-
- java.io.File
- All Implemented Interfaces:
-
Serializable
,Comparable<File>
public class File extends Object implements Serializable, Comparable<File>
An abstract representation of file and directory pathnames.
User interfaces and operating systems use system-dependent pathname strings to name files and directories. This class presents an abstract, system-independent view of hierarchical pathnames. An abstract pathname has two components:
- 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.
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:
- Serialized Form
Field Summary
Modifier and Type | Field | Description |
---|---|---|
static String | pathSeparator | The system-dependent path-separator character, represented as a string for convenience. |
static char | pathSeparatorChar | The system-dependent path-separator character. |
static String | separator | The system-dependent default name-separator character, represented as a string for convenience. |
static char | separatorChar | The system-dependent default name-separator character. |
Constructor Summary
Constructor | Description |
---|---|
File(File parent,
String child) | Creates a new |
File(String pathname) | Creates a new |
File(String parent,
String child) | Creates a new |
File(URI uri) | Creates a new |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
boolean | canExecute() | Tests whether the application can execute the file denoted by this abstract pathname. |
boolean | canRead() | Tests whether the application can read the file denoted by this abstract pathname. |
boolean | canWrite() | Tests whether the application can modify the file denoted by this abstract pathname. |
int | compareTo(File pathname) | Compares two abstract pathnames lexicographically. |
boolean | createNewFile() | Atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist. |
static File | createTempFile(String prefix,
String suffix) | Creates an empty file in the default temporary-file directory, using the given prefix and suffix to generate its name. |
static File | createTempFile(String prefix,
String suffix,
File directory) | Creates a new empty file in the specified directory, using the given prefix and suffix strings to generate its name. |
boolean | delete() | Deletes the file or directory denoted by this abstract pathname. |
void | deleteOnExit() | Requests that the file or directory denoted by this abstract pathname be deleted when the virtual machine terminates. |
boolean | equals(Object obj) | Tests this abstract pathname for equality with the given object. |
boolean | exists() | Tests whether the file or directory denoted by this abstract pathname exists. |
File | getAbsoluteFile() | Returns the absolute form of this abstract pathname. |
String | getAbsolutePath() | Returns the absolute pathname string of this abstract pathname. |
File | getCanonicalFile() | Returns the canonical form of this abstract pathname. |
String | getCanonicalPath() | Returns the canonical pathname string of this abstract pathname. |
long | getFreeSpace() | Returns the number of unallocated bytes in the partition named by this abstract path name. |
String | getName() | Returns the name of the file or directory denoted by this abstract pathname. |
String | getParent() | Returns the pathname string of this abstract pathname's parent, or |
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() | Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname. |
String[] | list(FilenameFilter filter) | Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter. |
File[] | listFiles() | Returns an array of abstract pathnames denoting the files in the directory denoted by this abstract pathname. |
File[] | listFiles(FileFilter filter) | Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter. |
File[] | listFiles(FilenameFilter filter) | Returns an array of abstract pathnames denoting the files and directories in the directory denoted by this abstract pathname that satisfy the specified filter. |
static File[] | listRoots() | List the available filesystem roots. |
boolean | mkdir() | Creates the directory named by this abstract pathname. |
boolean | mkdirs() | Creates the directory named by this abstract pathname, including any necessary but nonexistent parent directories. |
boolean | renameTo(File dest) | Renames the file denoted by this abstract pathname. |
boolean | setExecutable(boolean executable) | A convenience method to set the owner's execute permission for this abstract pathname. |
boolean | setExecutable(boolean executable,
boolean ownerOnly) | Sets the owner's or everybody's execute permission for this abstract pathname. |
boolean | setLastModified(long time) | Sets the last-modified time of the file or directory named by this abstract pathname. |
boolean | setReadable(boolean readable) | A convenience method to set the owner's read permission for this abstract pathname. |
boolean | setReadable(boolean readable,
boolean ownerOnly) | Sets the owner's or everybody's read permission for this abstract pathname. |
boolean | setReadOnly() | Marks the file or directory named by this abstract pathname so that only read operations are allowed. |
boolean | setWritable(boolean writable) | A convenience method to set the owner's write permission for this abstract pathname. |
boolean | setWritable(boolean writable,
boolean ownerOnly) | Sets the owner's or everybody's write permission for this abstract pathname. |
Path | toPath() | Returns a |
String | toString() | Returns the pathname string of this abstract pathname. |
URI | toURI() | Constructs a |
URL | toURL() | Deprecated. This method does not automatically escape characters that are illegal in URLs. |
Methods declared in class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
Field Detail
separatorChar
public static final char separatorChar
The system-dependent default name-separator character. This field is initialized to contain the first character of the value of the system property file.separator
. On UNIX systems the value of this field is '/'
; on Microsoft Windows systems it is '\\'
.
- See Also:
System.getProperty(java.lang.String)
separator
public static final String separator
The system-dependent default name-separator character, represented as a string for convenience. This string contains a single character, namely separatorChar
.
pathSeparatorChar
public static final char pathSeparatorChar
The system-dependent path-separator character. This field is initialized to contain the first character of the value of the system property path.separator
. This character is used to separate filenames in a sequence of files given as a path list. On UNIX systems, this character is ':'
; on Microsoft Windows systems it is ';'
.
- See Also:
System.getProperty(java.lang.String)
pathSeparator
public static final String pathSeparator
The system-dependent path-separator character, represented as a string for convenience. This string contains a single character, namely pathSeparatorChar
.
Constructor Detail
File
public 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
- A pathname string - Throws:
-
NullPointerException
- If thepathname
argument isnull
File
public 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
- The parent pathname string -
child
- The child pathname string - Throws:
-
NullPointerException
- Ifchild
isnull
File
public 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
- The parent abstract pathname -
child
- The child pathname string - Throws:
-
NullPointerException
- Ifchild
isnull
File
public 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.toURI()).equals( f.getAbsoluteFile())so long as the original abstract pathname, the URI, and the new abstract pathname are all created in (possibly different invocations of) the same Java virtual machine. This relationship typically does not hold, however, when a
file:
URI that is created in a virtual machine on one operating system is converted into an abstract pathname in a virtual machine on a different operating system.- Parameters:
-
uri
- An absolute, hierarchical URI with a scheme equal to"file"
, a non-empty path component, and undefined authority, query, and fragment components - Throws:
-
NullPointerException
- Ifuri
isnull
-
IllegalArgumentException
- If the preconditions on the parameter do not hold - Since:
- 1.4
- See Also:
-
toURI()
,URI
Method Detail
getName
public 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:
- 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
public 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:
- The pathname string of the parent directory named by this abstract pathname, or
null
if this pathname does not name a parent
getParentFile
public 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:
- 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
public 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:
- 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
public String 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 property user.dir
, is returned. Otherwise this pathname is resolved in a system-dependent way. On UNIX systems, a relative pathname is made absolute by resolving it against the current user directory. On Microsoft Windows systems, a relative pathname is made absolute by resolving it against the current directory of the drive named by the pathname, if 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
- Throws:
-
SecurityException
- If a required system property value cannot be accessed. - See Also:
isAbsolute()
getAbsoluteFile
public File getAbsoluteFile()
Returns the absolute form of this abstract pathname. Equivalent to new File(this.
.getAbsolutePath()
)
- Returns:
- 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. - Since:
- 1.2
getCanonicalPath
public String getCanonicalPath() throws IOException
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 -
SecurityException
- If a required system property value cannot be accessed, or if a security manager exists and itsSecurityManager.checkRead(java.io.FileDescriptor)
method denies read access to the file - Since:
- 1.1
- See Also:
Path.toRealPath(java.nio.file.LinkOption...)
getCanonicalFile
public File getCanonicalFile() throws IOException
Returns the canonical form of this abstract pathname. Equivalent to new 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 -
SecurityException
- If a required system property value cannot be accessed, or if a security manager exists and itsSecurityManager.checkRead(java.io.FileDescriptor)
method denies read access to the file - Since:
- 1.2
- See Also:
Path.toRealPath(java.nio.file.LinkOption...)
toURL
@Deprecated public URL toURL() throws MalformedURLException
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:
- 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()
,URI
,URI.toURL()
,URL
toURI
public 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
new File( f.toURI()).equals( f.getAbsoluteFile())so long as the original abstract pathname, the URI, and the new abstract pathname are all created in (possibly different invocations of) the same Java virtual machine. Due to the system-dependent nature of abstract pathnames, however, this relationship typically does not hold when a
file:
URI that is created in a virtual machine on one operating system is converted into an abstract pathname in a virtual machine on a different operating system. Note that when this abstract pathname represents a UNC pathname then all components of the UNC (including the server name component) are encoded in the URI
path. The authority component is undefined, meaning that it is represented as null
. The Path
class defines the toUri
method to encode the server name in the authority component of the resulting URI
. The toPath
method may be used to obtain a Path
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 - Throws:
-
SecurityException
- If a required system property value cannot be accessed. - Since:
- 1.4
- See Also:
-
File(java.net.URI)
,URI
,URI.toURL()
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 return true
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 - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkRead(java.lang.String)
method denies read access to the file
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 return true
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. - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method denies write access to the file
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 - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkRead(java.lang.String)
method denies read access to the file or directory
isDirectory
public boolean isDirectory()
Tests whether the file denoted by this abstract pathname is a directory.
Where it is required to distinguish an I/O exception from the case that the file is not a directory, or where several attributes of the same file are required at the same time, then the 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 - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkRead(java.lang.String)
method denies read access to the file
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 - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkRead(java.lang.String)
method denies read access to the file
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.
- Returns:
-
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 itsSecurityManager.checkRead(java.lang.String)
method denies read access to the file - 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 - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkRead(java.lang.String)
method denies read access to the file
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 the Files.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. - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkRead(java.lang.String)
method denies read access to the file
createNewFile
public boolean createNewFile() throws IOException
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 -
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method denies write access to the file - 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.
Note that the Files
class defines the delete
method to throw an IOException
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 - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkDelete(java.lang.String)
method denies delete access to the file
deleteOnExit
public void deleteOnExit()
Requests that the file or directory denoted by this abstract pathname be deleted when the virtual machine terminates. Files (or directories) are deleted in the reverse order that they are registered. Invoking this method to delete a file or directory that is already registered for deletion has no effect. Deletion will be attempted only for normal termination of the virtual machine, as defined by the Java Language Specification.
Once deletion has been requested, it is not possible to cancel the 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.
- Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkDelete(java.lang.String)
method denies delete access to the file - Since:
- 1.2
- See Also:
delete()
list
public 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.
Note that the Files
class defines the newDirectoryStream
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. - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkRead(String)
method denies read access to the directory
list
public 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
- 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. - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkRead(String)
method denies read access to the directory - See Also:
Files.newDirectoryStream(Path,String)
listFiles
public 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.
Note that the Files
class defines the newDirectoryStream
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. - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkRead(String)
method denies read access to the directory - Since:
- 1.2
listFiles
public 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
- 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. - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkRead(String)
method denies read access to the directory - Since:
- 1.2
- See Also:
Files.newDirectoryStream(Path,String)
listFiles
public 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
- 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. - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkRead(String)
method denies read access to the directory - Since:
- 1.2
- See Also:
Files.newDirectoryStream(Path,java.nio.file.DirectoryStream.Filter)
mkdir
public boolean mkdir()
Creates the directory named by this abstract pathname.
- Returns:
-
true
if and only if the directory was created;false
otherwise - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method does not permit the named directory to be created
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 - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkRead(java.lang.String)
method does not permit verification of the existence of the named directory and all necessary parent directories; or if theSecurityManager.checkWrite(java.lang.String)
method does not permit the named directory and all necessary parent directories to be created
renameTo
public boolean renameTo(File dest)
Renames the file denoted by this abstract pathname.
Many aspects of the behavior of this method are inherently platform-dependent: The rename operation might not be able to move a file from one filesystem to another, it might not be atomic, and it might not succeed if a file with the destination abstract pathname already exists. The return value should always be checked to make sure that the rename operation was successful.
Note that the Files
class defines the move
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:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method denies write access to either the old or new pathnames -
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 -
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method denies write access to the named file - 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 - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method denies write access to the named file - 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 operations -
ownerOnly
- 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. - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method denies write access to the named file - 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 invocation
file.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. - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method denies write access to the file - 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.
- Parameters:
-
readable
- Iftrue
, sets the access permission to allow read operations; iffalse
to disallow read operations -
ownerOnly
- 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 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. Ifreadable
isfalse
and the underlying file system does not implement a read permission, then the operation will fail. - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method denies write access to the file - 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 invocation
file.setReadable(arg, true)
- Parameters:
-
readable
- Iftrue
, sets the access permission to allow read operations; iffalse
to disallow read 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. Ifreadable
isfalse
and the underlying file system does not implement a read permission, then the operation will fail. - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method denies write access to the file - 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.
- Parameters:
-
executable
- Iftrue
, sets the access permission to allow execute operations; iffalse
to disallow execute operations -
ownerOnly
- 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 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. Ifexecutable
isfalse
and the underlying file system does not implement an execute permission, then the operation will fail. - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method denies write access to the file - 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 invocation
file.setExecutable(arg, true)
- Parameters:
-
executable
- Iftrue
, sets the access permission to allow execute operations; iffalse
to disallow execute 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. Ifexecutable
isfalse
and the underlying file system does not implement an execute permission, then the operation will fail. - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method denies write access to the file - 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 return true
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 - Throws:
-
SecurityException
- If a security manager exists and itsSecurityManager.checkExec(java.lang.String)
method denies execute access to the file - Since:
- 1.6
listRoots
public static File[] listRoots()
List the available filesystem roots.
A particular Java platform may support zero or more hierarchically-organized file systems. Each file system has a root
directory from which all other files in that file system can be reached. Windows platforms, for example, have a root directory for each active drive; UNIX platforms have a single root directory, namely "/"
. The set of available filesystem roots is affected by various system-level operations such as the insertion or ejection of removable media and the disconnecting or unmounting of physical or virtual disk drives.
This method returns an array of File
objects that denote the root directories of the available filesystem roots. It is guaranteed that the canonical pathname of any file physically present on the local machine will begin with one of the roots returned by this method.
The canonical pathname of a file that resides on some other machine and is accessed via a remote-filesystem protocol such as SMB or NFS may or may not begin with one of the roots returned by this method. 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, while File
objects containing UNC pathnames will not be returned by this method.
Unlike most methods in this class, this method does not throw security exceptions. If a security manager exists and its SecurityManager.checkRead(String)
method denies read access to a particular root directory, then that directory will not appear in the result.
- 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:
FileStore
getTotalSpace
public long getTotalSpace()
Returns the size of the partition named by this abstract pathname.
- Returns:
- 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 deniesRuntimePermission
("getFileSystemAttributes")
or itsSecurityManager.checkRead(String)
method denies read access to the file named by this abstract pathname - Since:
- 1.6
getFreeSpace
public long getFreeSpace()
Returns the number of unallocated bytes in the partition named by this abstract path name.
The returned number of unallocated bytes is a hint, but not a guarantee, that it is possible to use most or any of these 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. This value will be less than or equal to the total file system size returned bygetTotalSpace()
. - Throws:
-
SecurityException
- If a security manager has been installed and it deniesRuntimePermission
("getFileSystemAttributes")
or itsSecurityManager.checkRead(String)
method denies read access to the file named by this abstract pathname - Since:
- 1.6
getUsableSpace
public 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.
- Returns:
- 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 togetFreeSpace()
. - Throws:
-
SecurityException
- If a security manager has been installed and it deniesRuntimePermission
("getFileSystemAttributes")
or itsSecurityManager.checkRead(String)
method denies read access to the file named by this abstract pathname - Since:
- 1.6
createTempFile
public static File createTempFile(String prefix, String suffix, File directory) throws IOException
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"
. 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
- The prefix string to be used in generating the file's name; must be at least three characters long -
suffix
- The suffix string to be used in generating the file's name; may benull
, in which case the suffix".tmp"
will be used -
directory
- 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 characters -
IOException
- If a file could not be created -
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method does not allow a file to be created - Since:
- 1.2
createTempFile
public static File createTempFile(String prefix, String suffix) throws IOException
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)
.
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 long -
suffix
- 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 characters -
IOException
- If a file could not be created -
SecurityException
- If a security manager exists and itsSecurityManager.checkWrite(java.lang.String)
method does not allow a file to be created - Since:
- 1.2
- See Also:
Files.createTempDirectory(String,FileAttribute[])
compareTo
public 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.
- 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
public 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.
- Overrides:
-
equals
in classObject
- 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:
-
Object.hashCode()
,HashMap
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 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.
- Overrides:
-
hashCode
in classObject
- Returns:
- A hash code for this abstract pathname
- See Also:
-
Object.equals(java.lang.Object)
,System.identityHashCode(java.lang.Object)
toString
public String toString()
Returns the pathname string of this abstract pathname. This is just the string returned by the getPath()
method.
toPath
public Path toPath()
Returns a java.nio.file.Path
object constructed from this abstract path. The resulting Path
is associated with the default-filesystem
.
The first invocation of this method works as if invoking it were equivalent to evaluating the expression:
FileSystems.getDefault().getPath(this.getPath());Subsequent invocations of this method return the same
Path
. If this abstract pathname is the empty abstract pathname then this method returns a Path
that may be used to access the current user directory.
- 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:
Path.toFile()