do you mean in windows NT? system environment variables are shared by all users on a machine, user variables are per user.
normally you need a JDK installed, JAVA_HOME should point to the JDK and the JAVA_HOME\bin should be in your PATH. Try the java
IDE eclipse (www.eclipse.org) if you want your coding a little bit more comfortable.
SCJP 1.2, SCJD, SCEA, IBM 484, Weblogic 7