利用ArrayList进行的洗牌算法

算法思想

1. 先构造一副扑克牌；
2. 利用for循环从后往前依次取牌 i；
3. 从[0,i]用Random函数随机取一张扑克牌j；
4. 将i与j位置上的牌进行交换。

Java代码

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

class card{
    private String suit;
    private int rank;
    card(String suit,int rank){
        this.suit = suit;
        this.rank = rank;
    }

    @Override
    public String toString() {
        String num = String.format("%d",rank);
        switch(rank){
            case 11:
                num = "J";
                break;
            case 12:
                num = "Q";
                break;
            case 13:
                num = "K";
                break;
        }
        return suit + ":" + num;
    }
}
class cardDeam{
    //构造一副扑克牌
    String color[] = {"♥","♠","♣","♦"};

    public List<card> poker(){
        List<card> cards = new ArrayList<>();
        for(int i = 0;i < 4;i++){
            for(int j = 1;j <= 13;j++){
                card card = new card(color[i],j);
                cards.add(card);
            }
        }
        return cards;
    }
    //洗牌算法
    public void shufleCards(List<card> cards){
        //从后往前依次取牌i
        for(int i = cards.size() - 1;i > 0;i--){
            //设置随机种子，一般获取系统当前时间
            Random a = new Random(20191226);
            //从[0,i)随机取一张扑克牌j
            int j = a.nextInt(i);
            //将i和j位置上的牌进行交换
            swap(cards,i,j);
        }
    }
    //交换两张扑克牌的位置
    private void swap(List<card> cards,int i,int j){
        card temp = cards.get(i);
        cards.set(i,cards.get(j));
        cards.set(j,temp);
    }
}
public class Test20191226 {
    public static void main(String[] args) {
        cardDeam newcard = new cardDeam();
        List<card> cards = newcard.poker();
        System.out.println(cards);

        newcard.shufleCards(cards);
        System.out.println(cards);
    }
}

运行结果

洗牌前：
[♥:1, ♥:2, ♥:3, ♥:4, ♥:5, ♥:6, ♥:7, ♥:8, ♥:9, ♥:10, ♥:J, ♥:Q, ♥:K, 
 ♠:1, ♠:2, ♠:3, ♠:4, ♠:5, ♠:6, ♠:7, ♠:8, ♠:9, ♠:10, ♠:J, ♠:Q, ♠:K,
 ♣:1, ♣:2, ♣:3, ♣:4, ♣:5, ♣:6, ♣:7, ♣:8, ♣:9, ♣:10, ♣:J, ♣:Q, ♣:K,
 ♦:1, ♦:2, ♦:3, ♦:4, ♦:5, ♦:6, ♦:7, ♦:8, ♦:9, ♦:10, ♦:J, ♦:Q, ♦:K]

洗牌后：
[♥:10, ♠:1, ♠:5, ♠:2, ♥:Q, ♣:7, ♥:K, ♥:9, ♠:J, ♣:4, ♥:7, ♥:6, ♥:5,
 ♦:J, ♠:9, ♣:Q, ♦:3, ♦:K, ♠:8, ♥:8, ♦:5, ♦:4, ♦:1, ♥:4, ♠:K, ♣:10,
 ♦:9, ♣:5, ♠:Q, ♠:6, ♣:8, ♣:2, ♠:3, ♣:J, ♥:1, ♣:6, ♦:2, ♥:2, ♦:8,
 ♣:3, ♦:6, ♠:7, ♥:J, ♠:10, ♦:7, ♦:10, ♣:1, ♥:3, ♦:Q, ♣:K, ♠:4, ♣:9]