private void emitNewInstanceCallback(ClassEmitter ce) {
    CodeEmitter e = ce.begin_method(Constants.ACC_PUBLIC, SINGLE_NEW_INSTANCE, null);
    switch (callbackTypes.length) {
      case 0 -> {
        // TODO: make sure Callback is null
      }
      case 1 -> {
        // for now just make a new array; TODO: optimize
        e.push(1);
        e.newarray(CALLBACK);
        e.dup();
        e.push(0);
        e.load_arg(0);
        e.aastore();
        e.invoke_static_this(SET_THREAD_CALLBACKS);
      }
      default -> e.throw_exception(ILLEGAL_STATE_EXCEPTION, "More than one callback object required");
    }
    emitCommonNewInstance(e);
  }
private void emitNewInstanceCallback(ClassEmitter ce)