Creating References Using Inheritance Hierarchies

import java.util.*;
public class A { public String s() { return "A"; } }
public class B extends A { public String s() { return "B"; } }
List<A> list = new ArrayList<>();
list.add(new A());
list.add(new B());
for (A x : list) System.out.print(x.s());

• A

  Compile-time error

• B

  BB

• C

  AA

• D

  AB

  check_circle