Java300学习笔记（15）—— Collectios 工具类

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1 工具类 Collections 常用方法

• binarySearch(List<? extends Comparable<? super T>> list, T key),前提是容器要有序；
• sort()
• reverse()
• shuffle(List<?> list)
• swap(List<?> list, int i, int j)

1.1 测试洗牌

package day04.col;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class CollectionsDemo1 {

    public static void main(String[] args) {
        List<Integer> cards = new ArrayList<>();

        //洗牌，模拟斗地主
        for (int i = 0; i < 54; i++) {
            cards.add(i);
        }

        Collections.shuffle(cards);

        //依次发牌
        List<Integer> p1 = new ArrayList<>();
        List<Integer> p2 = new ArrayList<>();
        List<Integer> p3 = new ArrayList<>();
        List<Integer> last = new ArrayList<>();

        for (int i = 0; i < 51; i += 3) {
            p1.add(cards.get(i));
            p2.add(cards.get(i + 1));
            p3.add(cards.get(i + 2));
        }

        last.add(cards.get(51));
        last.add(cards.get(52));
        last.add(cards.get(53));

        System.out.println("第一个人：" + p1);
        System.out.println("第二个人：" + p2);
        System.out.println("第三个人：" + p3);
        System.out.println("底牌：" + last);

    }
}