File

File deals directly with files and the file system. File class describes the properties of a file or a directory itself.

A File object tells the information associated with a disk file, such as the permissions, time, date, and directory path, and to navigate subdirectory hierarchies.

A directory in Java is treated simply as a File with one additional property. A list of filenames that can be examined by the list( ) method.

File(String directoryPath): directoryPath is the path name of the file
File(String directoryPath, String filename): filename is the name of the file or subdirectory,
File(File dirObj, String filename): dirObj is a File object that specifies a directory
File(URI uriObj): uriObj is a URI object that describes a file.

File Object	Description
File f1 = new File("/");	f1 is constructed with a directory path as the only argument.
File f2 = new File("/","autoexec.bat");	f2 has the path and the filename.
File f3 = new File(f1,"autoexec.bat");	f3 refers to the same file as f2.

If you use a forward slash (/) on a Windows, the path will still resolve correctly. To use a backslash character (\), you will need to use its escape sequence (\\) within a string.

Constants from File class

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.

File Constructor

File(File parent, String child): Creates a new File instance from a parent abstract pathname and a child pathname string.
File(String pathname): Creates a new File instance by converting the given pathname string into an abstract pathname.
File(String parent, String child): Creates a new File instance from a parent pathname string and a child pathname string.
File(URI uri): Creates a new File instance by converting the given file: URI into an abstract pathname.

Is it executable, readable or writable

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.

Compare two file path

int compareTo(File pathname): Compares two abstract pathnames lexicographically.
boolean equals(Object obj): Tests this abstract pathname for equality with the given object.

Create a file

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.

Delete a file

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.

Is it a file or a directory

boolean isDirectory(): Tests whether the file denoted by this abstract pathname is a directory.
boolean isFile(): returns true if called on a file and false if called on a directory.

Whether the file or directory denoted by this abstract pathname exists

boolean exists(): Tests whether the file or directory denoted by this abstract pathname exists.

Whether this abstract pathname is absolute

boolean isAbsolute(): Tests whether this abstract pathname is absolute.

Is this file hidden

boolean isHidden(): Tests whether the file named by this abstract pathname is a hidden file.

Get the file last modified time

long lastModified(): Returns the time that the file denoted by this abstract pathname was last modified.

Get the file size

long length(): Returns the length of the file denoted by this abstract pathname.

Get file path and name

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.
String getName(): Returns the name of the file or directory denoted by this abstract pathname.
String getPath(): Converts this abstract pathname into a pathname string.

Get free space, total space, usable space

long getFreeSpace(): Returns the number of unallocated bytes in the partition named by this abstract path name.
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.

Get parent file

String getParent(): Returns the pathname string of this abstract pathname's parent, or null if this pathname does not name a parent directory.
File getParentFile(): Returns the abstract pathname of this abstract pathname's parent, or null if this pathname does not name a parent directory.

Return file in a directory

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.

Create new directories

boolean mkdir(): Creates the directory.
boolean mkdirs(): Creates the directory, including any necessary but nonexistent parent directories.

Rename file

boolean renameTo(File dest): Renames the file denoted by this abstract pathname.

Change to executable, readable, writable

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.

Change last-modified time

boolean setLastModified(long time): Sets the last-modified time of the file or directory named by this abstract pathname.

Get string representation of a file location

String toString(): Returns the pathname string of this abstract pathname.

Convert file location to URI and URL

URI toURI(): Creates a file: URI that represents this abstract pathname.

Revised from Open JDK source code