Does the VM ID objects in it's heap?

Question

Does the VM internally IDentify objects on its heap via a C structure or like? And if so, how does it manage immutable objects like multiple new Integer(1) and know to provide references to a pre-existing Integer object?

Answer 1

So what about this?
new Thread(new Runnable() {
        public void run() {
               Integer foo = new Integer(1);
               // now sleep, keeping i in scope
}).start();
// sleep for a while to ensure that foo exists in heap.
Integer  bar = new Integer(1);Now since Integer is immutable, do foo & bar both reference the same Integer instance? I would think they do, if so, where/how does a JVM know at the line of bar instantation that foo exists? Does it trace at the new call all referencable instances?