What OS version supports Java J2SE JRE, can Jaguar?

[Seacrest]

Sounds like what you may need to do is turn Java on in FireFox.
Go to Preferences and click the 'Content' tab.

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Java is built-in to OS X.
It is dependent on which version of the OS you are using.
AFAIK, it cannot be installed independently of the OS.

All Java in OS X is Java Runtime Environment 2, even if the version of the Virtual Machine says it is 1.x.

HTH.