You set environment variables for Java Plug-in in the following situations:
You installed Java Plug-in in a location other than the default installation directory (/usr/dt/appconfig/netscape).
You installed both Java Plug-in 1.2 and 1.1.2 on your system and want to specify which plug-in to use.
You want to use a JRE other than 1.2.1_03.
You want to view Java Plug-in tracing information (see "Displaying Java Plug-in Tracing Output").