目标：实现对Person 对象的年龄，从小到大排序
1、实现排序
1 package com.app; 2
3 import java.util.ArrayList; 4 import java.util.Collections; 5 import java.util.Comparator; 6 import java.util.List; 7
8 public class A1 { 9
10 public static void main(String[] args) { 11 List<Person> list = getData() ; 12 //排序
13 Collections.sort( list , comparator ); 14
15 for (Person person : list) { 16 System.out.println("person " + person.getName() + " " + person.getAge() ); 17 } 18
19 } 20
21 /**
22 * 年龄按从小到大排序 23 */
24 static Comparator<Person> comparator = new Comparator<Person>() { 25 @Override 26 public int compare(Person p1 , Person p2 ) { 27 if( p1.getAge() > p2.getAge() ){ 28 return 1 ; //正数
29 }else if ( p1.getAge() < p2.getAge()) { 30 return -1 ; //负数
31 }else { 32 return 0; //相等为0
33 } 34 } 35 }; 36
37 static private List<Person> getData() { 38 List<Person> list = new ArrayList<>() ; 39
40 Person p1 = new Person() ; 41 p1.setAge( 10 ); 42 p1.setName( "p1" ); 43
44 Person p2 = new Person() ; 45 p2.setAge( 30 ); 46 p2.setName( "p2" ); 47
48 Person p3 = new Person() ; 49 p3.setAge( 20 ); 50 p3.setName( "p3" ); 51
52 Person p4 = new Person() ; 53 p4.setAge( 15 ); 54 p4.setName( "p4" ); 55
56 list.add( p1 ) ; 57 list.add( p2 ) ; 58 list.add( p3 ) ; 59 list.add( p4 ) ; 60
61 return list ; 62 } 63 }
2、创建Person类
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; } }
3、运行结果（实现对年龄的排序）
person p1 10
person p4 15
person p3 20
person p2 30