Java(tm) Library Packages

Java provides many libraries to choose from Packages in Java are convenient ways of grouping related classes and interfaces. Packages eliminate potential conflicts between class names and enables modular groups of classes to be available only when needed. Classes within a package do not have to be closely related. Often classes within a package are designed to work together. Every class belongs to a package.

The java class libraries are divided into the following packages:

java.lang includes the most fundamental classes in the Java library. This package is so important to it is imported by default.
java.applet includes the classes needed to create applets that appear on World Wide Web pages.
java.awt is the Abstract Window Toolkit. This is Java's mapping package and creates windows that you can see displayed in some applets.
java.io includes the classes that perform file I/O which are type safe.
java.net includes the classes needed to perform low level I/O over the Internet.
java.util includes general utility classes such as Date.