Getting all instances of a class [duplicate]

Answer 1

Not in general. If you're using the debugger API it may be possible (I haven't checked) but you shouldn't use that other than for debugging.

If your design requires this, it's probably worth rethinking that design.

Answer 2

You can use a Factory static initializer when you instantiate your class (Singleton pattern) and then add each generated instance in the factory constructor to a List ...

Something like this :

  class MyObject {
    private static List instances = new ArrayList();

    public static MyObject createMyObject() {
    MyObject o = new MyObject();
    instances.add(new java.lang.ref.WeakReference(o));
    return o;
    }

    public static List getInstances() {
    return instances;
    }

    private MyObject() {
    // Not allowed 
    }
  }