class A<T> {
  private class B {
    int x;
  }
  B instance;
  A() {
    instance = new B();
  }
  void f(A p) {
    instance = p.instance;
  }
}

public static void main(String[] args)
{
  A<T1> x = new A<T1>();
  x.f(new A<T2>());
}