Discovering the Java API

Java is unique among most programming languages in that it comes standard with an extremely powerful set of classes. These classes offer features such as compressing data, playing sounds, and encrypting email messages.
To be precise, these features are not part of the actual Java language. They are part of the standard Java API, or Application Programming Interface. API is a general term used to describe a set of support programs that perform certain tasks. The Java API is a particularly rich API because of all the different features it offers.

The Java API is pretty massive, and is therefore organized into different parts called packages.
The following is a list of some of the more important Java API hierarchy, along with the types of features they support:

1. java.applet - general applet features
2. java.awt - windowing and GUI features
3. java.io - data input and output
4. java.lang - core Java language features
5. java.math - math routines
6. java.net - networking
7. java.security - security
8. java.text - text handling features
9. java.util - miscellaneous utility features

The Java 2 SDK documentation contains much more information about the classes and packages in the Java API. The Java API documentation is actually installed separately from the JDK, but it is installed into the same directory with the Java 2 SDK. Check out the file index.html in the docs. The complete documentation for the Java 2 API is available online at un's Java Web site.