16状态模式

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16状态模式

状态机又叫有限状态机，它有 3 个部分组成：状态、事件、动作
事件也称为转移条件。
事件触发状态的转移及动作的执行。
但动作不是必须的，可能只转移状态，不执行任何动作。

  • 分支逻辑
    简单、直接
  • 查表法
    适合状态多、状态转移复杂的状态机
    通过二维数组来表示状态转移图，极大提高可读性和可维护性
  • 状态模式
    适合状态并不多、状态转移比较简单，但事件触发执行的动作包含的业务逻辑比较复杂的状态机
    状态模式引入非常多状态类，会导致代码难维护

分支逻辑法

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public enum State {
  SMALL(0),
  SUPER(1),
  FIRE(2),
  CAPE(3);
  private int value;
  private State(int value) {
    this.value = value;
  }
  public int getValue() {
    return this.value;
  }
}

public class MarioStateMachine {
  private int score;
  private State currentState;
  public MarioStateMachine() {
    this.score = 0;
    this.currentState = State.SMALL;
  }
  public void obtainMushRoom() {
    if (currentState.equals(State.SMALL)) {
      this.currentState = State.SUPER;
      this.score += 100;
    }
  }
  public void obtainCape() {
    if (currentState.equals(State.SMALL) || currentState.equals(State.SUPER) ) {
      this.currentState = State.CAPE;
      this.score += 200;
    }
  }
  public void obtainFireFlower() {
    if (currentState.equals(State.SMALL) || currentState.equals(State.SUPER) ) {
      this.currentState = State.FIRE;
      this.score += 300;
    }
  }
  public void meetMonster() {
    if (currentState.equals(State.SUPER)) {
      this.currentState = State.SMALL;
      this.score -= 100;
      return;
    }
    if (currentState.equals(State.CAPE)) {
      this.currentState = State.SMALL;
      this.score -= 200;
      return;
    }
    if (currentState.equals(State.FIRE)) {
      this.currentState = State.SMALL;
      this.score -= 300;
      return;
    }
  }
  public int getScore() {
    return this.score;
  }
  public State getCurrentState() {
    return this.currentState;
  }
}


public class ApplicationDemo {
  public static void main(String[] args) {
    MarioStateMachine mario = new MarioStateMachine();
    mario.obtainMushRoom();
    int score = mario.getScore();
    State state = mario.getCurrentState();
    System.out.println("mario score: " + score + "; state: " + state);
  }
}

查表法

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public enum Event {
  GOT_MUSHROOM(0),
  GOT_CAPE(1),
  GOT_FIRE(2),
  MET_MONSTER(3);
  private int value;
  private Event(int value) {
    this.value = value;
  }
  public int getValue() {
    return this.value;
  }
}
public class MarioStateMachine {
  private int score;
  private State currentState;
  private static final State[][] transitionTable = {
          {SUPER, CAPE, FIRE, SMALL},
          {SUPER, CAPE, FIRE, SMALL},
          {CAPE, CAPE, CAPE, SMALL},
          {FIRE, FIRE, FIRE, SMALL}
  };
  private static final int[][] actionTable = {
          {+100, +200, +300, +0},
          {+0, +200, +300, -100},
          {+0, +0, +0, -200},
          {+0, +0, +0, -300}
  };
  public MarioStateMachine() {
    this.score = 0;
    this.currentState = State.SMALL;
  }
  public void obtainMushRoom() {
    executeEvent(Event.GOT_MUSHROOM);
  }
  public void obtainCape() {
    executeEvent(Event.GOT_CAPE);
  }
  public void obtainFireFlower() {
    executeEvent(Event.GOT_FIRE);
  }
  public void meetMonster() {
    executeEvent(Event.MET_MONSTER);
  }
  private void executeEvent(Event event) {
    int stateValue = currentState.getValue();
    int eventValue = event.getValue();
    this.currentState = transitionTable[stateValue][eventValue];
    this.score = actionTable[stateValue][eventValue];
  }
  public int getScore() {
    return this.score;
  }
  public State getCurrentState() {
    return this.currentState;
  }
}

状态模式

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public interface IMario { //所有状态类的接口
  State getName();
  //以下是定义的事件
  void obtainMushRoom();
  void obtainCape();
  void obtainFireFlower();
  void meetMonster();
}
public class SmallMario implements IMario {
  private MarioStateMachine stateMachine;
  public SmallMario(MarioStateMachine stateMachine) {
    this.stateMachine = stateMachine;
  }
  @Override
  public State getName() {
    return State.SMALL;
  }
  @Override
  public void obtainMushRoom() {
    stateMachine.setCurrentState(new SuperMario(stateMachine));
    stateMachine.setScore(stateMachine.getScore() + 100);
  }
  @Override
  public void obtainCape() {
    stateMachine.setCurrentState(new CapeMario(stateMachine));
    stateMachine.setScore(stateMachine.getScore() + 200);
  }
  @Override
  public void obtainFireFlower() {
    stateMachine.setCurrentState(new FireMario(stateMachine));
    stateMachine.setScore(stateMachine.getScore() + 300);
  }
  @Override
  public void meetMonster() {
    // do nothing...
  }
}
public class SuperMario implements IMario {
  private MarioStateMachine stateMachine;
  public SuperMario(MarioStateMachine stateMachine) {
    this.stateMachine = stateMachine;
  }
  @Override
  public State getName() {
    return State.SUPER;
  }
  @Override
  public void obtainMushRoom() {
    // do nothing...
  }
  @Override
  public void obtainCape() {
    stateMachine.setCurrentState(new CapeMario(stateMachine));
    stateMachine.setScore(stateMachine.getScore() + 200);
  }
  @Override
  public void obtainFireFlower() {
    stateMachine.setCurrentState(new FireMario(stateMachine));
    stateMachine.setScore(stateMachine.getScore() + 300);
  }
  @Override
  public void meetMonster() {
    stateMachine.setCurrentState(new SmallMario(stateMachine));
    stateMachine.setScore(stateMachine.getScore() - 100);
  }
}
// 省略CapeMario、FireMario类...
public class MarioStateMachine {
  private int score;
  private IMario currentState; // 不再使用枚举来表示状态
  public MarioStateMachine() {
    this.score = 0;
    this.currentState = new SmallMario(this);
  }
  public void obtainMushRoom() {
    this.currentState.obtainMushRoom();
  }
  public void obtainCape() {
    this.currentState.obtainCape();
  }
  public void obtainFireFlower() {
    this.currentState.obtainFireFlower();
  }
  public void meetMonster() {
    this.currentState.meetMonster();
  }
  public int getScore() {
    return this.score;
  }
  public State getCurrentState() {
    return this.currentState.getName();
  }
  public void setScore(int score) {
    this.score = score;
  }
  public void setCurrentState(IMario currentState) {
    this.currentState = currentState;
  }
}

单例状态

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public interface IMario {
  State getName();
  void obtainMushRoom(MarioStateMachine stateMachine);
  void obtainCape(MarioStateMachine stateMachine);
  void obtainFireFlower(MarioStateMachine stateMachine);
  void meetMonster(MarioStateMachine stateMachine);
}
public class SmallMario implements IMario {
  private static final SmallMario instance = new SmallMario();
  private SmallMario() {}
  public static SmallMario getInstance() {
    return instance;
  }
  @Override
  public State getName() {
    return State.SMALL;
  }
  @Override
  public void obtainMushRoom(MarioStateMachine stateMachine) {
    stateMachine.setCurrentState(SuperMario.getInstance());
    stateMachine.setScore(stateMachine.getScore() + 100);
  }
  @Override
  public void obtainCape(MarioStateMachine stateMachine) {
    stateMachine.setCurrentState(CapeMario.getInstance());
    stateMachine.setScore(stateMachine.getScore() + 200);
  }
  @Override
  public void obtainFireFlower(MarioStateMachine stateMachine) {
    stateMachine.setCurrentState(FireMario.getInstance());
    stateMachine.setScore(stateMachine.getScore() + 300);
  }
  @Override
  public void meetMonster(MarioStateMachine stateMachine) {
    // do nothing...
  }
}
// 省略SuperMario、CapeMario、FireMario类...
public class MarioStateMachine {
  private int score;
  private IMario currentState;
  public MarioStateMachine() {
    this.score = 0;
    this.currentState = SmallMario.getInstance();
  }
  public void obtainMushRoom() {
    this.currentState.obtainMushRoom(this);
  }
  public void obtainCape() {
    this.currentState.obtainCape(this);
  }
  public void obtainFireFlower() {
    this.currentState.obtainFireFlower(this);
  }
  public void meetMonster() {
    this.currentState.meetMonster(this);
  }
  public int getScore() {
    return this.score;
  }
  public State getCurrentState() {
    return this.currentState.getName();
  }
  public void setScore(int score) {
    this.score = score;
  }
  public void setCurrentState(IMario currentState) {
    this.currentState = currentState;
  }
}