Collections工具类

 1 import java.util.Collections;
 2 import java.util.LinkedList;
 3 import java.util.List;
 4 
 5 public class Test19 
 6 {
 7     public static void main(String[] args) 
 8     {
 9            List list=new LinkedList();//多态
10            for(int i=0;i<9;i++)//循环添加值
11            {
12                list.add("a"+i);
13            }
14            System.out.println(list);
15            
16            Collections.shuffle(list);//随机排列
17            System.out.println("随机排列:"+list);
18            
19            Collections.sort(list);//升序排列
20            System.out.println("升序排列:"+list);
21            
22            Collections.reverse(list);
23            System.out.println("逆序排列:"+list);
24     }
25 }