java随机算法（随机洗牌）

 

public class Card {
	public static final int DIAMOND = 0; // 方块(钻石)
	public final static int CLUB = 1; // 梅花
	public static final int HEART = 2; // 红桃(红心)
	public static final int SPADE = 3; // 黑桃(花锄)
	public static final int JOKER = 4; // 王
	
	public final static int THREE = 0;
	public final static int FOUR = 1;
	public final static int FIVE = 2;
	public final static int SIX = 3;
	public final static int SEVEN = 4;
	public final static int EIGHT = 5;
	public final static int NINE = 6;
	public final static int TEN = 7;
	public final static int JACK = 8;// J
	public final static int QUEEN = 9;// Q
	public final static int KING = 10;// K
	public final static int ACE = 11;// A
	public final static int DEUCE = 12; // 2
	public final static int BLACK = 13; // 小王
	public final static int COLOR = 14;// 大王
	
	/** 花色 0代表方块, 1代表梅花, 2代表红桃, 3代表黑桃,4:王 */
	private int suit;
	/** 点数 规定: 0代表3, 1代表4, 2代表5,... */
	private int rank;
	
	public Card() {
	}
	
	public Card(int suit, int rank) {
		// this.rank = rank;
		// this.suit = suit;
		setRank(rank);
		setSuit(suit);
	}
	
	public int getSuit() {
		return suit;
	}
	
	public void setSuit(int suit) {
		if (suit < DIAMOND || suit > JOKER)
			throw new RuntimeException("花色超过范围!");
		this.suit = suit;
	}
	
	public int getRank() {
		return rank;
	}
	
	public void setRank(int rank) {
		if (rank < THREE || rank > COLOR) {
			throw new RuntimeException("点数超过范围!");
		}
		this.rank = rank;
	}
	
	private static final String[] RANK_NAMES = { "3", "4", "5", "6", "7", "8",
		"9", "10", "J", "Q", "K", "A", "2", "小王", "大王" };
	private static final String[] SUIT_NAMES = { "方块", "梅花", "红桃", "黑桃", "" };
	
	// 覆盖Object 类的toStirng() 方法. 实现对象的文本描述
	public String toString() {
		return SUIT_NAMES[suit] + RANK_NAMES[rank];
	}
	
	public boolean equals(Object obj) {
		if (obj == null) {
			return false;
		}
		if (this == obj) {
			return true;
		}
		if (obj instanceof Card) {
			Card other = (Card) obj;
			return this.rank == other.rank && this.suit == other.suit;
		}
		return false;
	}
	
	public int hashCode() {
		// return suit*100+rank;
		// suit=3= 00000000 00000000 00000000 00000011
				// rank=10=00000000 00000000 00000000 00000011
		// suit<<16=00000000 00000011 00000000 00000000
		// 00000000 00000011 00000000 00000011
		return (suit << 16) + rank;// (x<<16)+y
	}

}

 

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

import org.junit.Test;

public class ShuffleCard {

	public static void swap(List<?> list, int i, int j) {
		final List l = list;
		l.set(i, l.set(j, l.get(i)));
	}
	
	//随机洗牌
	@Test
	public void testShuffle2() {
		List<Card> cards = new ArrayList<Card>();
		// 生成一副牌
		for (int rank = Card.THREE; rank <= Card.DEUCE; rank++) {
			cards.add(new Card(Card.DIAMOND, rank));
			cards.add(new Card(Card.CLUB, rank));
			cards.add(new Card(Card.HEART, rank));
			cards.add(new Card(Card.SPADE, rank));
		}
		cards.add(new Card(Card.JOKER, Card.BLACK));
		cards.add(new Card(Card.JOKER, Card.COLOR));
		System.out.println(cards.toString());
		
		Random random = new Random();
		for (int i = cards.size(); i > 1; i--) {
			int m = random.nextInt(i);
			swap(cards, i - 1, m);
		}
		System.out.println(cards.toString());
	}

}

 生成结果：

 

[方块3, 梅花3, 红桃3, 黑桃3, 方块4, 梅花4, 红桃4, 黑桃4, 方块5, 梅花5, 红桃5, 黑桃5, 方块6, 梅花6, 红桃6, 黑桃6, 方块7, 梅花7, 红桃7, 黑桃7, 方块8, 梅花8, 红桃8, 黑桃8, 方块9, 梅花9, 红桃9, 黑桃9, 方块10, 梅花10, 红桃10, 黑桃10, 方块J, 梅花J, 红桃J, 黑桃J, 方块Q, 梅花Q, 红桃Q, 黑桃Q, 方块K, 梅花K, 红桃K, 黑桃K, 方块A, 梅花A, 红桃A, 黑桃A, 方块2, 梅花2, 红桃2, 黑桃2, 小王, 大王]

[红桃8, 方块5, 梅花2, 方块4, 小王, 梅花5, 黑桃2, 方块Q, 黑桃A, 黑桃J, 红桃K, 梅花4, 方块J, 梅花A, 黑桃5, 方块3, 红桃9, 红桃Q, 黑桃K, 方块7, 梅花Q, 梅花6, 红桃J, 方块9, 方块6, 方块8, 黑桃Q, 梅花K, 梅花9, 方块K, 红桃5, 红桃3, 黑桃8, 方块10, 大王, 红桃2, 梅花10, 黑桃10, 黑桃3, 黑桃6, 红桃4, 黑桃9, 红桃6, 梅花8, 梅花7, 红桃10, 黑桃7, 方块A, 黑桃4, 梅花J, 红桃A, 梅花3, 方块2, 红桃7]