Swap.java

class A {
  private String name = null;
  public A(String newName) {
    name = newName;
  }
  public void Assign(A other) {
    name = other.name;
  }
  public void SayHi() {
    System.out.println("Hello from " + name);
  }
}
 
 
class Swap {
  public static void swap(A a1, A a2) {
    A temp = new A("");
    temp.Assign(a1);
    a1.Assign(a2);
    a2.Assign(temp);
  }

  public static void main(String[] args) {
    A a1 = new A("Dog");
    A a2 = new A("Cat");
    A a3 = a1;
    swap(a1,a2);
    a1.SayHi();
    a2.SayHi();
    a3.SayHi();
    if (a3 == a2) {
      System.out.println("Real pass-by-reference swap");
    } else {
      System.out.println("Fake pass-by-value swap");
    }
  }
}