Java runtime environments sprout like mushrooms after a rainstorm.

Very few software companies trust the JRE already installed on the target machine, so they bundle their own copy with their software and omit the option in the installer that lets the sysadmin opt out of installing that particular component.

This results in a single server having up to a dozen independent copies of the JRE that are identical down to the binary level, save their locations in the disk array.