23种设计模式之状态模式

Posted 2020-10-03 java_pro

状态模式（State）：当一个对象的内在状态改变时，允许改变其行为，这个对象看起来像是改变了其类。

 

package designMode.state;

class Context {
    
    private State state;

    public Context(State state) {
        this.state = state;
    }
    /**
     * 对请求做处理，并设置下一状态
     */
    public void request(){
        state.handle(this);
    }
    /***************getter&setter****************************/
    public State getState() {
        return state;
    }
    public void setState(State state) {
        this.state = state;
        System.out.println("当前状态："+state.getClass().getSimpleName());
    }
}

package designMode.state;

interface State {
    
    void handle(Context context);
}

package designMode.state;

class ConcreteStateA implements State{

    @Override
    public void handle(Context context) {
        context.setState(new ConcreteStateB());
    }
}
class ConcreteStateB implements State{
    
    @Override
    public void handle(Context context) {
        context.setState(new ConcreteStateA());
    }
}

package designMode.state;

class Test {
    public static void main(String[] args) {
        Context c = new Context(new ConcreteStateA());
        
        c.request();
        c.request();
        c.request();
        c.request();
    }
}