Accessing Files and Directories - Beginning Java 2 SDK - page 356

Querying Files and Directories

The following basic set of methods are provided for examining the file or directory that is identified by
a File object:

Method Description

exists() Returns true if the file or directory referred to by the File

object exists and false otherwise.

isDirectory() Returns true if the File object refers to an existing directory

and false otherwise.

isFile() Returns true if the File object refers to an existing file and

false otherwise.

isHidden()

Returns true if the File object refers to a file that is hidden
and false otherwise. How a file is hidden is system-dependent.
Under Unix a hidden file has a name that begins with a dot.
Under Windows a file is hidden if it is marked as such within the
file system.

canRead() Returns true if you are permitted to read the file referred to by

the File object, and false otherwise. This method can throw a
SecurityException if read access to the file is not permitted.

canWrite()

Returns true if you are permitted to write to the file referred to
by the File object and false otherwise. This method may also
throw a SecurityException if you are not allowed to write to
the file.

getAbsolutePath() Returns the absolute path for the directory or file referenced by

the current File object. If the object contains an absolute path,
then the string returned by getPath() is returned. Otherwise,
under MS Windows the path is resolved against the current
directory for the drive identified by the pathname, or against the
current user directory if no drive letter appears in the pathname,
and against the current user directory under UNIX.

getAbsoluteFile()

Returns a File object containing the absolute path for the
directory or file referenced by the current File object.

When you are working with a File object, you may not know whether it contains an absolute or a
relative path. However, you may well want to get hold of its parent directory - to create another file for
instance. For a File object created from a relative path, the getParent() method will return null .
In this case you can use the getAbsolutePath() method to obtain the absolute path, or the
getAbsoluteFile() method to ensure that you have a File object for which the getParent()
method will return a string representing the complete path for the parent directory. For instance:

File dataFile = new File("output.txt");