图解设计模式-Strategy模式

Posted 2021-01-04 use-d

Strategy（算法）模式可以整体的替换算法的实现部分。

 

重点说明：

使用委托这种弱关联关系可以很方便的整体替换算法。

 

角色:

Strategy策略：该角色负责决定实现策略所需要的接口api。

ConcreteStrategy具体策略：该角色负责实现Strategy角色接口api。即负责实现具体的策略。

Context上下文：负责使用Strategy角色，Context角色保存了ConcreteStrategy角色的实例，并使用ConcreteStrategy角色去实现需求。

 

代码：

public class Hand {

    public static final int GUU = 0;
    public static final int CHO = 1;
    public static final int PAA = 2;

    public static final Hand[] hand = {
            new Hand(GUU),
            new Hand(CHO),
            new Hand(PAA),
    };

    private int handValue;
    private Hand(int handValue) {
        this.handValue = handValue;
    }

    private static final String[] name = {
      "石头","剪刀","布"
    };
    public static Hand getHand(int handValue) {
        return hand[handValue];
    }

    public boolean isStrongerThan(Hand h){
        return fight(h)== 1;
    }

    public boolean isWeakerThan(Hand h) {
        return fight(h)== -1;
    }

    private int fight(Hand h) {
        if(this==h){
            return 0;
        }else if((this.handValue+1)%3==h.handValue) {
            return 1;
        }else{
         return -1;
        }
    }
}

public interface Strategy {
    public abstract Hand nextHand();
    public abstract void study(boolean win);
}

public class ProbStrategy implements Strategy {

    private Random random;
    private int preHandValue = 0;
    private int currentHandValue =0;

    private int[][] histroy = {
            {1,1,1},
            {1,1,1},
            {1,1,1}
    };

    public ProbStrategy(int seed) {
        this.random = new Random(seed);
    }

    private int getSum(int hv) {
        int sum = 0;
        for(int i=0;i<3;i++) {
            sum +=histroy[hv][i];
        }
        return sum;
    }

    @Override
    public Hand nextHand() {
        int bet = random.nextInt(getSum(currentHandValue));
        int handvalue = 0;
        if(bet<histroy[currentHandValue][0]) {
            handvalue=0;
        }else if(bet<histroy[currentHandValue][0] + histroy[currentHandValue][1]) {
            handvalue  =1;
        }else {
            handvalue = 2;
        }
        preHandValue=currentHandValue;
        currentHandValue = handvalue;
        return Hand.getHand(handvalue);
    }

    @Override
    public void study(boolean win) {
        if(win){
            histroy[preHandValue][currentHandValue]++;
        }else {
            histroy[preHandValue][(currentHandValue+1)%3]++;
            histroy[preHandValue][(currentHandValue+2)%3]++;
        }
    }
}

public class WinningStrategy implements Strategy {

    private Random random;
    private  boolean won =false;
    private Hand preHand;

    public WinningStrategy(int seed) {
        this.random = new Random(seed);
    }
    @Override
    public Hand nextHand() {
        if(!won) {
            preHand = Hand.getHand(random.nextInt(3));
        }
        return preHand;
    }

    @Override
    public void study(boolean win) {
        won = win;
    }
}

public class Main {
    public static void main(String[] args){

        int seed0=1;
        int seed1=2;

        Play play1 = new Play("王五",new WinningStrategy(seed0));
        Play play2 = new Play("王五",new ProbStrategy(seed1));

        for(int i=0;i<1000;i++) {
            Hand hand1 = play1.nextHand();
            Hand hand2 = play2.nextHand();
            if(hand1.isStrongerThan(hand2)) {
                System.out.println("winner is "+play1);
                play1.win();
                play2.lose();
            }else if(hand2.isStrongerThan(hand1)) {
                System.out.println("winner is "+play2);
                play2.win();
                play1.lose();
            }else {
                System.out.println("even... ");
                play2.even();
                play1.even();
            }
        }
    }
}

执行结果：

winner is [王五:0 ganmes,0 win, 0 lose ]
even...
even...
winner is [王五:3 ganmes,1 win, 0 lose ]
even...
even...
even...
winner is [王五:7 ganmes,2 win, 0 lose ]
winner is [王五:8 ganmes,3 win, 0 lose ]
winner is [王五:9 ganmes,0 win, 4 lose ]
winner is [王五:10 ganmes,4 win, 1 lose ]
winner is [王五:11 ganmes,1 win, 5 lose ]
winner is [王五:12 ganmes,5 win, 2 lose ]
winner is [王五:13 ganmes,2 win, 6 lose ]
even...