The class java.io.File should really be called “Filename” since most of its methods are concerned with querying and adjusting filename, and pathname information, not the contents of a file. File can't actually do any I/O. Directory, filename and pathname information is often called “metadata,” meaning “data about data.” Methods of java.io.File allow you to access metadata to:
Return a File object from a String containing a pathname
Test whether a file exists, is readable/writable, or is a directory
Say how many bytes are in the file and when it was last modified
Delete the file, or create directory paths
Get various forms of the file pathname.
Here are all the important public members of java.io.File. Method ...