e107. determining when an object is no longer used.txt

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) {
    }