Look at impressive speed improvement and better internal optimization (including reduced memory footprint) on the Sun Java page. Follow the link, you'll see that it provides you access to the Java JRE 1.4.

You may alternatively install the JDK (which contains the JRE plus the Java SDK). Look on the Sun's web site for it.

Note that Java is installed side by side: there's no real upgrade, just a second distinct installation of the JRE or the JDK. You may use the control panel to select your active JRE, or use the JAVA_HOME environment variable to select which JRE or JDK you want to use.

So don't overwrite Java in the same directory for the upgrade:
- if you have enough storage, use a new folder, you may uninstall the elder version later without breaking the new install.
- else, uninstall Java prior to installing the new version if you want to specify the same directory as before.