状态模式

1. 状态角色抽象类

public abstract class AbstractState {
    protected Context context;
    public void setContext(Context context) {
        this.context = context;
    }
    public abstract void handle1();
    public abstract void handle2();
}

2. 状态角色抽象类实现类

public  class ConcreteState1  extends AbstractState{
    @Override
    public void handle1() {
        //本状态逻辑处理
    }
    @Override
    public void handle2() {
        super.context.setCurrentState(Context.STATE2);
        super.context.handle2();
    }
}
public class ConcreteState2 extends AbstractState {
    @Override
    public void handle1() {
        super.context.setCurrentState(Context.STATE1);
        super.context.handle1();
    }
    @Override
    public void handle2() {
        //本状态逻辑处理
    }
}

3. 状态环境角色

public class Context {
    public static final AbstractState STATE1= new ConcreteState1();
    public static final AbstractState STATE2= new ConcreteState2();
    //当前状态角色
    private AbstractState currentState;
    public AbstractState getCurrentState() {
        return currentState;
    }
    public void setCurrentState(AbstractState currentState) {
        this.currentState = currentState;
        //切换状态
        this.currentState.setContext(this);
    }
    //切换状态方法
    public void handle1(){
        this.currentState.handle1();
    }
    public void handle2(){
        this.currentState.handle2();
    }
}

4. 场景使用

    Context context = new Context();
    AbstractState state1 =new ConcreteState1();
    state1.setContext(context);