Setting Up the CLASSPATH Variable
All the Java programs that you write rely on two kinds of class files: the classes you create and the Java class library, a set of hundreds of classes that represent the functionality of the Java language.
The Java Development Kit needs to know where to find Java class files on your system. In many cases, the kit can figure this out on its own by looking in the folder where it was installed.
You also can set it up yourself by creating or modifying another environment variable: CLASSPATH.
Setting the CLASSPATH on Windows 98 or Me
If you have compiled and run the HelloUser program successfully, the Java Development Kit has been configured successfully. You don't need to make any more changes to your system.