英文含义就是 “洗牌” 。shuffle（）方法常用于类似 洗牌要打乱顺序 的问题。
eg: 模拟洗牌
import java.util.*;
public class Card {
public static enum Face {
红心, 方块 , 草花, 黑桃
};
public static enum Deck {
one, two, three, four, five, six, seven, eight, nine, ten , eleven, tweleve, thirteen
};
/**
*
* 私有变量将从枚举Face, Deck中获得值，那么其返回值应该定义成枚举（ enum)吗？ 是的，但是需要使用Face face, Deck
* deck;
*
*/
private Face face;
private Deck deck;
public Card(Face faceVal, Deck deckVal) {
face = faceVal;
deck = deckVal;
}
public String toString() {
// return String.format("%s of %s", deck, face);
return String. format(face + " " + deck);
}
public static void main(String argc[]) {
Card card[] = new Card[52];
int counter = 0;
for (Card.Face faceVal : Card.Face. values()) {
for (Card.Deck deckVal : Card.Deck.values()) {
card[counter++] = new Card(faceVal, deckVal);
}
}
List<Card> list = Arrays. asList(card); // 将数组转化成collection
Collections. shuffle(list); // 利用集合（collections）的静态方法，打乱list集合顺序
Card[] card2 = new Card[52]; // 创建新数组
list.toArray(card2); // 将collection转换成数组，以便输出
for (Card c : card2) {
System. out.println(c + " ");
}
}
}
