[stupid question] setting env variables globally

[Aryeh M. Friedman]

Is there any way to set the default value of a enviromental variable
globally.   Specifically I want JAVA_VERSION to default to "1.6" unless
the user sets it other wise.   By global I mean no matter how something
is invoked (command line, script, GUI, IPC trigger, etc.) if it checks
the value of the var it gets the same value (and I want to do this
system wide)