java List 排序 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; } public String getAge() {  return age; } public void setAge(String age) {  this.age = age; } public String getName() {  return name; } public void setName(String name) {  this.name = name; } }

//具体的比较类，实现Comparator接口

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<userlist.size();i++){   User user_temp=(User)userlist.get(i);      System.out.println(user_temp.getAge()+","+user_temp.getName());   }   }}

 //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