The Java class library contains thousands of predefined classes and interfaces that programmers can use to write their own applications. These classes are grouped into packages based on their functionality. For example, the classes and interfaces used for file processing are grouped into the
java.io package, and the classes and interfaces for networking applications are grouped into the
java.net package. The Java API documentation lists the
protected members of each class and the
public members of each interface in the Java class library. The documentation overviews all the classes and interfaces, summarizes their members (i.e., the fields, constructors and methods of classes, ...