In Java the object doesn't get removed from memory until the Java VM
runs a garbage collector.

It's possible to evoke the garbage collector from Java, but
utilimately the VM has control over the object.

Try this (although I doubt this will help) :

set myCollection=Nothing

The thing about collections is that you often end up using them
globally.

Probably what you need to do is iterate over your collection, set each
member to Nothing, then set the collection to Nothing.