Simple demonstration of the State pattern. : State Pattern « Design Pattern « Java Tutorial

1. Java Tutorial
2. Design Pattern
3. State Pattern

interface State {
  void operation1();

  void operation2();

  void operation3();
}

class ServiceProvider {
  private State state;

  public ServiceProvider(State state) {
    this.state = state;
  }

  public void changeState(State newState) {
    state = newState;
  }

  public void service1() {
    state.operation1();
    state.operation3();
  }

  public void service2() {
    state.operation1();
    state.operation2();
  }

  public void service3() {
    state.operation3();
    state.operation2();
  }
}

class Implementation1 implements State {
  public void operation1() {
    System.out.println("Implementation1.operation1()");
  }

  public void operation2() {
    System.out.println("Implementation1.operation2()");
  }

  public void operation3() {
    System.out.println("Implementation1.operation3()");
  }
}

class Implementation2 implements State {
  public void operation1() {
    System.out.println("Implementation2.operation1()");
  }

  public void operation2() {
    System.out.println("Implementation2.operation2()");
  }

  public void operation3() {
    System.out.println("Implementation2.operation3()");
  }
}

public class StateDemo {
  static void run(ServiceProvider sp) {

  }

  public static void main(String args[]) {
    ServiceProvider sp = new ServiceProvider(new Implementation1());
    sp.service1();
    sp.service2();
    sp.service3();
    sp.changeState(new Implementation2());
    sp.service1();
    sp.service2();
    sp.service3();
  }
}