It's easy to install JRE (Java Runtime Environment) on linux. Below are step-by-step on how to do that.
(1) Get a JRE installer from java.sun.com
(2) Change as a superuser with this command
(3) Go to the directory where JRE would be installed. For a sample
(4) Change the JRE installer mode so the installer can be execute by linux
chmod a+x jre-1_4_2_09_linux.bin
(5) Execute an installer