State 状态

根据状态决定行为
state状态抽象为接口，内有m种行为（抽象方法），n个子类再实现这些行为。事务本身的类聚合状态，在内部的M种方法中调用state的实例即可

State 状态 - 图1

public class State {
    public static void main(String[] args) {
        States states = new Happy();
        MM m = new MM(states);
        m.Smile();
        m.Say();
    }
}
interface States{
    void Smile();
    void Say();
}
class MM{
    States states;
    public MM(States states) {
        this.states = states;
    }
    void  Smile(){
        states.Smile();
    }
    void Say(){
        states.Say();
    }
}
class Happy implements States{
    @Override
    public void Smile() {
        System.out.println("HappyMM Smile");
    }
    @Override
    public void Say() {
        System.out.println("HappyMM Say");
    }
}