In regards to weird things you can do with the JVM: You can actually allocate memory outside of the garbage collect from inside pure Java code. (Unsafe.allocate

In regards to weird things you can do with the JVM: You can actually allocate memory outside of the garbage collect from inside pure Java code. (Unsafe.allocateMemory, specifically. or you can use ByteBuffers, but I'm not sure which one is faster or if a ByteBuffer still interacts with the GC) This can allow you to deal with "objects" which are entirely outside of the GC, and can actually be a decent chunk faster then using normal objects. I did a microtest recently (which can mean absolutely nothing in practice) where allocating two normal objects and doing something with them was about 30% slower than dealing with memory outside the GC. As for the other things you mentioned, those are actually pretty routine. At least in some places. If you're working on a game, then you're going to be reusing objects and calling native functions as a normal thing :)