File

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.

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 ';'.

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.

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 '\\'.

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.

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.

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.

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())

canExecute

public boolean canExecute ()

Tests whether the application can execute the file denoted by this abstract pathname.

canRead

public boolean canRead ()

Tests whether the application can read the file denoted by this abstract pathname.

canWrite

public boolean canWrite ()

Tests whether the application can modify the file denoted by this abstract pathname.

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.

createNewFile

public boolean createNewFile ()

Atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist. The check for the existence of the file and the creation of the file if it does not exist are a single operation that is atomic with respect to all other filesystem activities that might affect the file.

Note: this method should not be used for file-locking, as the resulting protocol cannot be made to work reliably. The FileLock facility should be used instead.

createTempFile

public 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. If this method returns successfully then it is guaranteed that:

1. The file denoted by the returned abstract pathname did not exist before this method was invoked, and
2. Neither this method nor any of its variants will return the same abstract pathname again in the current invocation of the virtual machine.

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.

createTempFile

public 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. 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.

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.

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.

Note that on Android, the application lifecycle does not include VM termination, so calling this method will not ensure that files are deleted. Instead, you should use the most appropriate out of:

• Use a finally clause to manually invoke delete().
• Maintain your own set of files to delete, and process it at an appropriate point in your application's lifecycle.
• Use the Unix trick of deleting the file as soon as all readers and writers have opened it. No new readers/writers will be able to access the file, but all existing ones will still have access until the last one closes the file.

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.

exists

public boolean exists ()

Tests whether the file or directory denoted by this abstract pathname exists.

getAbsoluteFile

public File getAbsoluteFile ()

Returns the absolute form of this abstract pathname. Equivalent to new File(this.getAbsolutePath()).

getAbsolutePath

public String getAbsolutePath ()

Returns the absolute path of this file. An absolute path is a path that starts at a root of the file system. On Android, there is only one root: /.

A common use for absolute paths is when passing paths to a Process as command-line arguments, to remove the requirement implied by relative paths, that the child must have the same working directory as its parent.

getCanonicalFile

public File getCanonicalFile ()

Returns the canonical form of this abstract pathname. Equivalent to new File(this.getCanonicalPath()).

getCanonicalPath

public String getCanonicalPath ()

Returns the canonical pathname string of this abstract pathname.

A canonical pathname is both absolute and unique. The precise definition of canonical form is system-dependent. This method first converts this pathname to absolute form if necessary, as if by invoking the getAbsolutePath() method, and then maps it to its unique form in a system-dependent way. This typically involves removing redundant names such as "." and ".." from the pathname, resolving symbolic links (on UNIX platforms), and converting drive letters to a standard case (on Microsoft Windows platforms).

Every pathname that denotes an existing file or directory has a unique canonical form. Every pathname that denotes a nonexistent file or directory also has a unique canonical form. The canonical form of the pathname of a nonexistent file or directory may be different from the canonical form of the same pathname after the file or directory is created. Similarly, the canonical form of the pathname of an existing file or directory may be different from the canonical form of the same pathname after the file or directory is deleted.

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.

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.

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.

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.

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.

getTotalSpace

public long getTotalSpace ()

Returns the size of the partition named by this abstract pathname.

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.

On Android (and other Unix-based systems), this method returns the number of free bytes available to non-root users, regardless of whether you're actually running as root, and regardless of any quota or other restrictions that might apply to the user. (The getFreeSpace method returns the number of bytes potentially available to root.)

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.

isAbsolute

public boolean isAbsolute ()

Tests whether this abstract pathname is absolute. The definition of absolute pathname is system dependent. On Android, absolute paths start with the character '/'.

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.

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.

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.

lastModified

public long lastModified ()

Returns the time that the file denoted by this abstract pathname was last modified.

Where it is required to distinguish an I/O exception from the case where 0L is returned, or where several attributes of the same file are required at the same time, or where the time of last access or the creation time are required, then the Files.readAttributes method may be used.

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.

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.

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.

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.

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.

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.

listRoots

public static File[] listRoots ()

Returns the file system roots. On Android and other Unix systems, there is a single root, /.

mkdir

public boolean mkdir ()

Creates the directory named by this abstract pathname.

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.

renameTo

public boolean renameTo (File dest)

Renames the file denoted by this abstract pathname.

Many failures are possible. Some of the more likely failures include:

• Write permission is required on the directories containing both the source and destination paths.
• Search permission is required for all parents of both paths.
• Both paths be on the same mount point. On Android, applications are most likely to hit this restriction when attempting to copy between internal storage and an SD card.

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.

setExecutable

public boolean setExecutable (boolean executable, 
                boolean ownerOnly)

Sets the owner's or everybody's execute permission for this abstract pathname.

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.

setExecutable

public boolean setExecutable (boolean executable)

A convenience method to set the owner's execute permission for this abstract pathname.

An invocation of this method of the form file.setExcutable(arg) behaves in exactly the same way as the invocation

     file.setExecutable(arg, true) 

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.

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. Whether or not a read-only file or directory may be deleted depends upon the underlying system.

setReadable

public boolean setReadable (boolean readable)

A convenience method to set the owner's read permission for this abstract pathname.

An invocation of this method of the form file.setReadable(arg) behaves in exactly the same way as the invocation

     file.setReadable(arg, true) 

setReadable

public boolean setReadable (boolean readable, 
                boolean ownerOnly)

Sets the owner's or everybody's read permission for this abstract pathname.

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.

setWritable

public boolean setWritable (boolean writable, 
                boolean ownerOnly)

Sets the owner's or everybody's write permission for this abstract pathname.

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.

setWritable

public boolean setWritable (boolean writable)

A convenience method to set the owner's write permission for this abstract pathname.

An invocation of this method of the form file.setWritable(arg) behaves in exactly the same way as the invocation

     file.setWritable(arg, true) 

toPath

public Path toPath ()

Returns a java.nio.file.Path object constructed from the 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());
 

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.

toString

public String toString ()

Returns the pathname string of this abstract pathname. This is just the string returned by the getPath() method.

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())

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.

toURL

public URL toURL ()

This method was deprecated in API level 15.
This method does not automatically escape characters that are illegal in URLs. It is recommended that new code convert an abstract pathname into a URL by first converting it into a URI, via the toURI method, and then converting the URI into a URL via the URI.toURL method.

Converts this abstract pathname into a file: URL. The exact form of the URL is system-dependent. If it can be determined that the file denoted by this abstract pathname is a directory, then the resulting URL will end with a slash.