集合内部先实现按年龄排序再实现以姓名排序

Posted 2020-08-19 沙弥

定义一个实体存放需要排序的数据

package ListAscByCollectionsMethod;
/*
 * 定义一个实体，存放数据。
 */
public 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;
     } 

}

实现comparator接口，定义排序规则：

package ListAscByCollectionsMethod;

import java.util.Comparator;
/*
 * 定义一个排序规则
 */
public class ComparatorUser implements Comparator{

    @Override
    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;
          }  
    }
}

测试定义的排序规则：

package ListAscByCollectionsMethod;

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

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"));
          
          for (int i=0;i<userlist.size();i++){
               User user_temp=(User)userlist.get(i);
                  System.out.print(user_temp.getAge()+"/"+user_temp.getName()+"\t"); 
              }
          System.out.println();
          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()); 
          }
          
         }

}

运行：

无排序结果：

4/dd 1/aa 5/ee 2/bb 5/ff 3/cc 6/gg

有排序结果：
1,aa 2,bb 3,cc 4,dd 5,ee 5,ff 6,gg