instanceof attempts to downcast : instanceof Operator « Operators « SCJP

1. SCJP
2. Operators
3. instanceof Operator

class A { }

class MainClass extends A {
  public static void main (String [] args) {
    A myA = new MainClass();
    m2(myA);
  }
  public static void m2(A a) {
    if (a instanceof MainClass)
      ((MainClass)a).doBstuff();
  }
  public static void doBstuff() {
    System.out.println("'a'");
  }
}

'a'