private static void emitGetCallback(ClassEmitter ce, int[] keys) {
    final CodeEmitter e = ce.begin_method(Constants.ACC_PUBLIC, GET_CALLBACK, null);
    e.load_this();
    e.invoke_static_this(BIND_CALLBACKS);
    e.load_this();
    e.load_arg(0);
    e.process_switch(keys, new ProcessSwitchCallback() {
      @Override
      public void processCase(int key, $Label end) {
        e.getfield(getCallbackField(key));
        e.goTo(end);
      }
      @Override
      public void processDefault() {
        e.pop(); // stack height
        e.aconst_null();
      }
    });
    e.return_value();
    e.end_method();
  }
private static void emitGetCallback(ClassEmitter ce, int[] keys)