Java I/O

The File Class

Instances of the java.io.File class represent filenames on the local system, not actual files. Occasionally, this distinction is crucial. For instance, File objects can represent directories as well as files. Also, you cannot assume that a file exists just because you have a File object for a file.

public class File extends Object implements Serializable

In Java 2, the File class also implements the java.lang.Comparable interface:

public class File extends Object implements Serializable, Comparable // Java 2

Although there are no guarantees that a file named by a File object actually exists, the File class does contain many methods for getting information about the attributes of a file and for manipulating those files. The File class attempts to account for system-dependent features like the file separator character and file attributes, though in practice it doesn’t do a very good job, especially in Java 1.0 and 1.1.

Each File object contains a single String field called path that contains either a relative or absolute path to the file, including the name of the file or directory itself:

private String path

Many methods in this class work solely by looking at this string. They do not necessarily look at any part of the filesystem.

Constructing File Objects

The java.io.File class has three constructors. Each accepts some variation of a filename as an argument. This one is the simplest:

public File(String path)

The path argument should be either an absolute or relative path ...