OnJava8-Examples/patterns/state/StateMachineDemo.java

// patterns/state/StateMachineDemo.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
// The StateMachine pattern and Template method
// {java patterns.state.StateMachineDemo}
package patterns.state;
import onjava.Nap;

interface State {
  void run();
}

abstract class StateMachine {
  protected State currentState;
  protected abstract boolean changeState();
  // Template method:
  protected final void runAll() {
    while(changeState()) // Customizable
      currentState.run();
  }
}

// A different subclass for each state:

class Wash implements State {
  @Override
  public void run() {
    System.out.println("Washing");
    new Nap(0.5);
  }
}

class Spin implements State {
  @Override
  public void run() {
    System.out.println("Spinning");
    new Nap(0.5);
  }
}

class Rinse implements State {
  @Override
  public void run() {
    System.out.println("Rinsing");
    new Nap(0.5);
  }
}

class Washer extends StateMachine {
  private int i = 0;
  // The state table:
  private State[] states = {
    new Wash(), new Spin(),
    new Rinse(), new Spin(),
  };
  Washer() { runAll(); }
  @Override
  public boolean changeState() {
    if(i < states.length) {
      // Change the state by setting the
      // surrogate reference to a new object:
      currentState = states[i++];
      return true;
    } else
      return false;
  }
}

public class StateMachineDemo {
  public static void main(String[] args) {
    new Washer();
  }
}
/* Output:
Washing
Spinning
Rinsing
Spinning
*/