Go to the Java website, choose the JRE or JDK based on your platform and needs. Download the requisite .bin files and upload them to the serveradmin home folder. For older versions go to the Java Archives site.
Steps for JRE and JDK are both the same. Here is an example of a JRE setup,
su - serveradmin # If you are not already serveradmin cd ~ # Switch to the serveradmin home directory chmod +x jre-6u16-linux-i586.bin ./jre-6u14-linux-i586.bin # Decompresses JRE to the current folder under jre1.6.0_16.
64-bit Java is not recommended at the moment due to significant loss in performance. If 64-bit Java is used, as a convention, we recommend adding to the default folder name _64-bit. In the above example, it would be, jre1.6.0_16_64-bit.