Java 中Comparator 的使用，实现集合排序

 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 }

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;
    }
}