Is there anything like VirtualEnv for Java?

Question

Is there anything similar to Python virtualenv for Java or JVM Languages?

Answer 1

I'm confused by the assertion that "Java doesn't have the concept of a 'system-wide installed' library". What would you call the jar files in $JAVA_HOME/jre/lib and $JAVA_HOME/jre/lib/ext?

Regardless of whether or not Java "needs" a tool like virtualenv, it seems that something that allowed you to quickly switch between different Java environments (e.g. Java 6 with such-and-such security extensions, Java 7, etc.) would be handy - even if all it was actually doing under the covers was manipulating the PATH, JAVA_HOME, and CLASSPATH env variables.