Collection

java.util.Collections:是集合工具类

作用：Collections不是集合，而是集合的工具类

常用API

addAll

package Collections;

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

public class CollectionsDemo {
    public static void main(String[] args) {
        ArrayList<String> list = new ArrayList<>();
        //添加到数组里面
        Collections.addAll(list,"aaa","sasa","gdg","gfd","hgf","fds","reg");
        System.out.println(list);
    }
}

shuffle

package Collections;

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

public class CollectionsDemo {
    public static void main(String[] args) {
        ArrayList<String> list = new ArrayList<>();
        //添加到数组里面
        Collections.addAll(list,"aaa","sasa","gdg","gfd","hgf","fds","reg");
        System.out.println("打乱前："+list);
        Collections.shuffle(list);
        System.out.println("打乱后："+list);
    }
}

随机取名的实现

package Collections;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Random;

public class CollectionDemo2 {
    public static void main(String[] args) {
        ArrayList<String> list1 = new ArrayList<>();
        Collections.addAll(list1,"撒娇了","萨马卡罗","大撒大撒","的撒旦","改好发给","发你回家","客家话");
        ArrayList<String> list2 = new ArrayList<>();
        for (int j = 1 ; j <= 10;j++) {
            System.out.println("------第"+j+"轮开始------");
            int count = list1.size();
            Random rd = new Random();
            for (int i = 0; i < count; i++) {
                int index = rd.nextInt(list1.size());
                String name = list1.remove(index);
                list2.add(name);
                System.out.println(name);
            }
            list1.addAll(list2);
            list2.clear();
        }
    }
}