package com.app;

 import java.util.ArrayList;

 import java.util.Collections;

 import java.util.Comparator;

 import java.util.List;

 public class A1 {

     public static void main(String[] args) {

         List<Person> list = getData() ;

         //排序

         Collections.sort( list , comparator );

         for (Person person : list) {

             System.out.println("person   " + person.getName() + "  " + person.getAge() );

         }

     }

     /**

      * 年龄按从小到大排序

      */

     static Comparator<Person> comparator = new Comparator<Person>() {

         @Override

         public int compare(Person p1 , Person p2 ) {

             if( p1.getAge() > p2.getAge() ){

               return 1 ;  //正数

             }else if ( p1.getAge() < p2.getAge()) {

                 return -1 ;  //负数

             }else {

                 return 0;  //相等为0

             }

         }

     };

     static private List<Person> getData() {

         List<Person> list = new ArrayList<>() ;

         Person p1 = new Person() ;

         p1.setAge( 10 );

         p1.setName( "p1" );

         Person p2 = new Person() ;

         p2.setAge( 30 );

         p2.setName( "p2" );

         Person p3 = new Person() ;

         p3.setAge( 20 );

         p3.setName( "p3" );

         Person p4 = new Person() ;

         p4.setAge( 15 );

         p4.setName( "p4" );

         list.add( p1 ) ;

         list.add( p2 ) ;

         list.add( p3 ) ;

         list.add( p4 ) ;

         return list ;

     }

 }

package com.app;

public class Person {

    private int age ;

    private String name ;

    public int getAge() {

        return age;

    }

    public void setAge(int age) {

        this.age = age;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

}