To be able to use Java compiler and JVM you need to have several environment
variables set:

JAVA_HOME -- top directory where you unpacked
your J2SDK or JRE distribution
PATH -- a colon separated list of directories
containing executable programs. Should contain
${JAVA_HOME}/bin directory
CLASSPATH -- a list of directories which contain
classes, and/or a list jar files with classes.

For example, your .profile file could have: