public class UnlockedSt implements State {
  private static UnlockedSt instance = new UnlockedSt();
  public static State createInstance() {
    return instance;
  }
  private UnlockedSt() {}
  public State coin(Mediator m) {
    m.thankyou();
    return UnlockedSt.createInstance();
  }
  public State pass(Mediator m) {
    m.lock();
    return LockedSt.createInstance();
  }
}