Collections.sort() 对 List 排序

java List 排序 Collections.sort() 对 List 排序

//一个POJO例子

class User {
 String name;
 String age;
 
 public User(String name,String age){
  this.name=name;
  this.age=age;
 }
}

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

public class ComparatorUser implements Comparator{

 public int compare(Object arg0, Object arg1) {
  User user0=(User)arg0;
  User user1=(User)arg1;

   //首先比较年龄，如果年龄相同，则比较名字

  int flag=user0.getAge().compareTo(user1.getAge());
  if(flag==0){
   return user0.getName().compareTo(user1.getName());
  }else{
   return flag;
  }  
 }
 
}

//测试类

public class SortTest { 

 public static void main(String[] args){
  List userlist=new ArrayList();
  userlist.add(new User("dd","4"));
  userlist.add(new User("aa","1"));
  userlist.add(new User("ee","5"));
  userlist.add(new User("bb","2"));  
  userlist.add(new User("ff","5"));
  userlist.add(new User("cc","3"));
  userlist.add(new User("gg","6"));
  
  ComparatorUser comparator=new ComparatorUser();
  Collections.sort(userlist, comparator);
   
  for (int i=0;i
  
   

 //首先年龄排序，如果年龄相同，则按名字排序
   


   
结果:
 1, aa
 2, bb
 3, cc
 4, dd
 5, ee //注意:同样是5岁的人，则比较名字(ee,ff)，然后排序
 5, ff
 6, gg