Java 设计模式系列(22) —— 状态模式

public abstract class State {
    // 封装环境对象
    protected Context context;
    
    public void setContext(Context _context) {
        this.context = _context;
    }
    
    // 定义状态下行为的忌口
    public abstract void action();
}

public class ConcreteState1 extends State {
    // 实现一个状态所定义的行为
    @Override
    public void action() {
        System.out.println("The action of concrete state1");
    }
}

public class ConcreteState2 extends State {
    @Override
    public void action() {
        System.out.println("the action of concrete state2");
    }
}

public class Context {
    public static State STATE1 = new ConcreteState1();
    public static State STATE2 = new ConcreteState2();
    // 具体状态类实例
    private State currentState;
    // 给出环境状态现有对象
    public State getCurrentState() {
        return currentState;
    }
    // 状态的切换
    public void setCurrentState(State _currentState) {
        this.currentState = _currentState;
        currentState.setContext(this);
    }
    
    // 定义客户端需要的接口
    public void handle1() {
        this.setCurrentState(STATE1);
        currentState.action();
    }
    // 定义客户端需要的接口
    public void handle12() {
        this.setCurrentState(STATE2);
        currentState.action();
    }
}