Java实现状态模式

一、简介

1、定义

状态模式 (State Pattern)是一种行为型设计模式，允许对象在内部状态改变时改变它的行为。通过定义状态接口和具体状态类，将对象的状态和行为分开，使得状态改变时可以改变行为。

2、状态模式的结构

状态模式涉及以下几个角色：
State（状态接口）：定义了状态类的共同接口，所有具体的状态类都实现这个接口。
ConcreteState（具体状态类）：每个具体的状态类实现了State接口，并定义了在该状态下的具体行为。
Context（上下文）：上下文类维护一个当前状态的引用，它通常会委托给具体的状态类来执行相应的状态切换。

二、Java实现案例

1、电灯开关状态案例

/**
 * @Description: 状态接口
 * @Date: 2025-02-07 17:09
 * @Author: gaoyufei
 **/
public interface State {
    void handle(Switch context);
}

/**
 * @Description: 关灯状态
 * @Date: 2025-02-07 17:12
 * @Author: gaoyufei
 **/
public class CloseState implements State{
    @Override
    public void handle(Switch switcher) {
        switcher.setState(new OpenState());
        System.out.println("开灯了");
    }
}
/**
 * @Description: 开灯状态
 * @Date: 2025-02-07 17:11
 * @Author: gaoyufei
 **/
public class OpenState implements State{
    @Override
    public void handle(Switch switcher) {
        switcher.setState(new CloseState());
        System.out.println("关灯了");
    }
}
/**
 * @Description: 开关，持有灯的状态
 * @Date: 2025-02-07 17:08
 * @Author: gaoyufei
 **/
public class Switch {
    private State state;
    public Switch(State state){
        this.state=state;
    }
    public void setState(State state){
        this.state=state;
    }
    public void press(){
        state.handle(this);
    }
}

/**
 * @Description: 操作人
 * @Date: 2025-02-07 17:14
 * @Author: gaoyufei
 **/
public class Operator {
    public static void main(String[] args) throws InterruptedException {
        Switch switcher=new Switch(new CloseState());//初始状态是关灯
        //模拟每隔1秒按压一下开关
        while (true){
            Thread.sleep(1000);
            switcher.press();
        }
    }
}

2、番茄工作法状态案例

/**
 * @Description: 番茄状态接口
 * @Date: 2025-02-08 10:49
 * @Author: gaoyufei
 **/
public interface TomatoState {
    void deal(Worker worker);
}

/**
 * @Description: 番茄-工作状态类
 * @Date: 2025-02-08 10:51
 * @Author: gaoyufei
 **/
public class WorkTomatoState implements TomatoState {
    @Override
    public void deal(Worker worker) {
        System.out.println("休息结束了，开始工作吧");
        try {
            Thread.sleep(25*60*1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("工作了25分钟");
        worker.setTomatoState(new RestTomatoState());
    }
}

/**
 * @Description: 番茄-休息状态类
 * @Date: 2025-02-08 10:53
 * @Author: gaoyufei
 **/
public class RestTomatoState implements TomatoState{
    @Override
    public void deal(Worker worker) {
        System.out.println("工作结束了，好好休息吧");
        try {
            Thread.sleep(5*60*1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("休息了5分钟");
        worker.setTomatoState(new WorkTomatoState());
    }
}

/**
 * @Description: 工作者
 * @Date: 2025-02-08 10:51
 * @Author: gaoyufei
 **/
public class Worker {
    private TomatoState tomatoState;
    public Worker(TomatoState tomatoState){
        this.tomatoState=tomatoState;
    }
    public void setTomatoState(TomatoState tomatoState){
        this.tomatoState=tomatoState;
    }
    public void startTomatoClock(){
        this.tomatoState.deal(this);
    }
}

/**
 * @Description: 客户端
 * @Date: 2025-02-08 11:02
 * @Author: gaoyufei
 **/
public class Client {
    public static void main(String[] args) {
        Worker worker=new Worker(new WorkTomatoState());
        while (true){
            worker.startTomatoClock();
        }
    }
}

3、电梯状态案例

这是一个简单的电梯系统。电梯的状态有关门、开门、上升、下降、停止。每个状态下电梯的行为不同。通过状态模式，根据电梯的不同状态执行不同的行为。

/**
 * @Description: 电梯状态接口
 * @Date: 2025-02-08 9:02
 * @Author: gaoyufei
 **/
public interface ElevatorState {
    void openDoor();
    void closeDoor();
    void moveUp();
    void moveDown();
    void stop();
}
/**
 * @Description: 关门状态
 * @Date: 2025-02-08 9:05
 * @Author: gaoyufei
 **/
public class CloseState implements ElevatorState {
    private Elevator elevator;
    public CloseState(Elevator elevator){
        this.elevator=elevator;
    }
    @Override
    public void openDoor() {
        System.out.println("电梯门开了");
        elevator.setCurrentState(elevator.getOpenState());
    }
    @Override
    public void closeDoor() {
        System.out.println("电梯门已经关了");
    }
    @Override
    public void moveUp() {
        System.out.println("电梯上升");
        elevator.setCurrentState(elevator.getMovingUpState());
    }
    @Override
    public void moveDown() {
        System.out.println("电梯下降");
        elevator.setCurrentState(elevator.getMovingDownState());
    }
    @Override
    public void stop() {
        System.out.println("电梯停止");
        elevator.setCurrentState(elevator.getStopState());
    }
}

/**
 * @Description: 开门状态
 * @Date: 2025-02-08 9:07
 * @Author: gaoyufei
 **/
public class OpenState implements ElevatorState{
    private Elevator elevator;
    public OpenState(Elevator elevator){
        this.elevator=elevator;
    }
    @Override
    public void openDoor() {
        System.out.println("电梯门已经打开");
    }
    @Override
    public void closeDoor() {
        System.out.println("电梯门关了");
        elevator.setCurrentState(elevator.getCloseState());
    }
    @Override
    public void moveUp() {
        System.out.println("电梯门打开状态,不能上升");
    }
    @Override
    public void moveDown() {
        System.out.println("电梯门打开状态,不能下降");
    }
    @Override
    public void stop() {
        System.out.println("电梯门打开状态,不能变换为停止状态");
    }
}

/**
 * @Description: 停止状态
 * @Date: 2025-02-08 9:59
 * @Author: gaoyufei
 **/
public class StopState implements ElevatorState{
    private Elevator elevator;
    public StopState(Elevator elevator){
        this.elevator=elevator;
    }
    @Override
    public void openDoor() {
        System.out.println("电梯门开了");
        elevator.setCurrentState(elevator.getOpenState());
    }
    @Override
    public void closeDoor() {
        System.out.println("电梯门关了");
        elevator.setCurrentState(elevator.getCloseState());
    }
    @Override
    public void moveUp() {
        System.out.println("电梯上升");
        elevator.setCurrentState(elevator.getMovingUpState());
    }
    @Override
    public void moveDown() {
        System.out.println("电梯下降");
        elevator.setCurrentState(elevator.getMovingDownState());
    }
    @Override
    public void stop() {
        System.out.println("电梯停止");
    }
}
/**
 * @Description: 上升状态
 * @Date: 2025-02-08 9:07
 * @Author: gaoyufei
 **/
public class MovingUpState implements ElevatorState{
    private Elevator elevator;
    public MovingUpState(Elevator elevator){
        this.elevator=elevator;
    }
    @Override
    public void openDoor() {
        System.out.println("电梯正在上升，不能开门");
    }
    @Override
    public void closeDoor() {
        System.out.println("电梯已经关门");
    }
    @Override
    public void moveUp() {
        System.out.println("电梯正在上升");
    }
    @Override
    public void moveDown() {
        System.out.println("电梯下降");
        elevator.setCurrentState(elevator.getMovingDownState());
    }
    @Override
    public void stop() {
        System.out.println("电梯停止");
        elevator.setCurrentState(elevator.getStopState());
    }
}

/**
 * @Description: 下降状态
 * @Date: 2025-02-08 9:08
 * @Author: gaoyufei
 **/
public class MovingDownState implements ElevatorState{
    private Elevator elevator;
    public MovingDownState(Elevator elevator){
        this.elevator=elevator;
    }
    @Override
    public void openDoor() {
        System.out.println("电梯正在下降,不能开门");
    }
    @Override
    public void closeDoor() {
        System.out.println("电梯正在下降,已经关门了");
    }
    @Override
    public void moveUp() {
        System.out.println("电梯上升");
        elevator.setCurrentState(elevator.getMovingUpState());
    }
    @Override
    public void moveDown() {
        System.out.println("电梯正在下降");
    }
    @Override
    public void stop() {
        System.out.println("电梯停止");
        elevator.setCurrentState(elevator.getStopState());
    }
}

/**
 * @Description: 电梯
 * @Date: 2025-02-08 9:04
 * @Author: gaoyufei
 **/
public class Elevator {
    private ElevatorState closeState;
    private ElevatorState openState;
    private ElevatorState movingDownState;
    private ElevatorState movingUpState;
    private ElevatorState stopState;

    private ElevatorState currentState;

    public Elevator(){
        closeState=new CloseState(this);
        openState=new OpenState(this);
        movingDownState=new MovingDownState(this);
        movingUpState=new MovingUpState(this);
        stopState=new StopState(this);
        currentState=closeState;// 默认初始状态为关闭状态

    }
    public void setCurrentState(ElevatorState currentState) {
        this.currentState = currentState;
    }
    public ElevatorState getCloseState() {
        return closeState;
    }
    public ElevatorState getOpenState() {
        return openState;
    }
    public ElevatorState getMovingDownState() {
        return movingDownState;
    }
    public ElevatorState getMovingUpState() {
        return movingUpState;
    }
    public ElevatorState getStopState() {
        return stopState;
    }
    public void openDoor(){
        currentState.openDoor();
    }
    public void closeDoor(){
        currentState.closeDoor();
    }
    public void moveUp(){
        currentState.moveUp();
    }
    public void moveDown(){
        currentState.moveDown();
    }
    public void stop(){
        currentState.stop();
    }
}

/**
 * @Description: 客户端
 * @Date: 2025-02-08 9:29
 * @Author: gaoyufei
 **/
public class Client {
    public static void main(String[] args) {
        //初始关闭状态
        Elevator elevator=new Elevator();
        //关门
        elevator.closeDoor();//输出 电梯门已经关了
        //开门
        elevator.openDoor();//输出 电梯门开了
        //上升
        elevator.moveUp();//输出 电梯门打开状态不能上升
        //关门
        elevator.closeDoor();//输出 电梯门关了
        //上升
        elevator.moveUp();//输出 电梯上升
        //关门
        elevator.closeDoor();//输出 电梯已经关门
        //下降
        elevator.moveDown();//输出 电梯下降
        //停止
        elevator.stop();//输出 电梯停止
        //开门
        elevator.openDoor();//输出 电梯门开了
        //停止
        elevator.stop();//输出 电梯门打开状态,不能变换为停止状态
    }
}