这里面包含了一百多个JAVA源文件

				A weak reference is used to determine when an object is no longer being referenced. 
				    // Create the weak reference.
				    ReferenceQueue rq = new ReferenceQueue();
				    WeakReference wr = new WeakReference(object, rq);
				    
				    // Wait for all the references to the object.
				    try {
				        while (true) {
				            Reference r = rq.remove();
				            if (r == wr) {
				                // Object is no longer referenced.
				            }
				        }
				    } catch (InterruptedException e) {
				    }