enum实战之石头剪刀布

本文通过实现一个简单的“石头剪刀布”程序，熟悉Java枚举类型（enum）多路分发的使用。

需要用到的类主要是以下四个：

1. 游戏主体RoShamBo：包括ROCK，SCISSORS，PAPER三种动作；
2. 对战结果Outcome：包括WIN，LOSE，DRAW三种对战结果；
3. 对战接口Competitor：包括对战方法compete()；
4. 逻辑验证RoShamBoSample：随机生成对战数据，验证对战结果。

详细代码如下：

1，Outcome.java:

package com.sample.roshambo;

public enum Outcome {
    WIN, LOSE, DRAW;
}

2，Competitor.java：

package com.sample.roshambo;

public interface Competitor<T extends Competitor<T>> {
    Outcome compete(T competitor);
}

3，RoShamBo.java：

package com.sample.roshambo;

public enum RoShamBo implements Competitor<RoShamBo> {

    ROCK(Outcome.DRAW, Outcome.WIN, Outcome.LOSE), SCISSORS(Outcome.LOSE, Outcome.DRAW, Outcome.WIN), PAPER(
            Outcome.WIN, Outcome.LOSE, Outcome.DRAW);

    private Outcome vsRock, vsScissors, vsPaper;

    private RoShamBo(Outcome vsRock, Outcome vsScissors, Outcome vsPaper) {
        this.vsRock = vsRock;
        this.vsScissors = vsScissors;
        this.vsPaper = vsPaper;
    }

    @Override
    public Outcome compete(RoShamBo competitor) {
        switch (competitor) {
            default:
            case ROCK:
                return vsRock;
            case SCISSORS:
                return vsScissors;
            case PAPER:
                return vsPaper;
        }
    }

}

4，RoShamBoSample：

package com.sample.roshambo;

import java.util.Random;

public class RoShamBoSample {

    private static final int MATCH_NUM = 10;

    private static <T extends Enum<T>> T random(Class<T> enumClass) {
        T[] values = enumClass.getEnumConstants();
        if (values.length < 1) {
            throw new IllegalArgumentException(enumClass.getSimpleName() + " has no constant");
        }
        return values[new Random().nextInt(values.length)];
    }

    private static <T extends Enum<RoShamBo> & Competitor<T>> Outcome match(T competitor1, T competitor2) {
        Outcome outcome = competitor1.compete(competitor2);
        System.out.println(competitor1 + " VS " + competitor2 + " : " + outcome);
        return outcome;
    }

    public static void main(String[] args) {
        for (int i = 0; i < MATCH_NUM; i++) {
            RoShamBo roShamBo1 = random(RoShamBo.class);
            RoShamBo roShamBo2 = random(RoShamBo.class);
            match(roShamBo1, roShamBo2);
        }
    }

}

其中一次的验证数据如下：

SCISSORS VS SCISSORS : DRAW
PAPER VS SCISSORS : LOSE
PAPER VS ROCK : WIN
SCISSORS VS ROCK : LOSE
SCISSORS VS SCISSORS : DRAW
PAPER VS ROCK : WIN
PAPER VS PAPER : DRAW
PAPER VS ROCK : WIN
SCISSORS VS ROCK : LOSE
PAPER VS ROCK : WIN