The Java Class Library

Java contains an extensive library of pre-written classes you can use in your programs. These classes are divided into groups called packages.

The Java 1.1 packages

• java.applet
• java.awt
• java.awt.datatransfer
• java.awt.event
• java.awt.image
• java.awt.peer
• java.beans
• java.io
• java.lang
• java.lang.reflect
• java.math
• java.net
• java.rmi
• java.rmi.dgc
• java.rmi.registry
• java.rmi.server
• java.security
• java.security.acl
• java.security.interfaces
• java.sql
• java.text
• java.util
• java.util.zip

Each package defines a number of classes, interfaces, exceptions, and errors.

Packages can be split into sub-packages. for example, the java.lang package has a sub-package called java.lang.reflect. These are really completely different packages. A class in a sub-package has no more access to a class in the parent package (or vice versa) than it would to a class in a completely different package.