Will the following code compile(class hierarchy)? : Questions « Object Oriented « SCJP

1. SCJP
2. Object Oriented
3. Questions

class X { void do1() { } }
  class Y extends X { void do2() { } }
 
  public class MainClass {
    public static void main(String [] args) {
      X x1 = new X();
      X x2 = new Y();
      Y y1 = new Y();
      ((Y)x2).do2();
   }
 }