java比较器

 1 package com.sun;
 2
 3 public class ComparatorDemo implements Comparable<ComparatorDemo> {
 4
 5     private String name;
 6     private Integer age;
 7     private float score;
 8
 9     public ComparatorDemo(String name, Integer age, float score) {
10         super();
11         this.name = name;
12         this.age = age;
13         this.score = score;
14     }
15
16     @Override
17     public String toString() {
18         return "name:" + name + ";age:" + age + ";score:" + score;
19     }
20
21     @Override
22     public int compareTo(ComparatorDemo o) {
23         if (this.score > o.score)// score是private的，为什么能够直接调用,这是因为在Student类内部
24             return -1;// 由高到底排序
25         else if (this.score < o.score)
26             return 1;
27         else {
28             if (this.age > o.age)
29                 return 1;// 由底到高排序
30             else if (this.age < o.age)
31                 return -1;
32             else
33                 return 0;
34         }
35     }
36
37     public String getName() {
38         return name;
39     }
40
41     public void setName(String name) {
42         this.name = name;
43     }
44
45     public Integer getAge() {
46         return age;
47     }
48
49     public void setAge(Integer age) {
50         this.age = age;
51     }
52
53     public float getScore() {
54         return score;
55     }
56
57     public void setScore(float score) {
58         this.score = score;
59     }
60
61 }

 1 package com.sun;
 2
 3 import java.util.ArrayList;
 4 import java.util.Arrays;
 5 import java.util.Collections;
 6 import java.util.List;
 7
 8 public class ComparatorTest {
 9
10     public static void main(String[] args) {
11         List<ComparatorDemo> lists = new ArrayList<>();
12         lists.add(new ComparatorDemo("a", 4, 4));
13         lists.add(new ComparatorDemo("b", 3, 6));
14         lists.add(new ComparatorDemo("c", 2, 3));
15         lists.add(new ComparatorDemo("d", 1, 7));
16         Collections.sort(lists);
17         for (ComparatorDemo comparatorDemo : lists) {
18             System.out.println("++++++" + comparatorDemo);
19         }
20
21         ComparatorDemo com[] = {new ComparatorDemo("a", 4, 4),
22                 new ComparatorDemo("b", 3, 6),
23                 new ComparatorDemo("c", 2, 3),
24                 new ComparatorDemo("d", 1, 7)};
25         Arrays.sort(com);
26         for (ComparatorDemo comparatorDemo : com) {
27             System.out.println("------" + comparatorDemo);
28         }
29     }
30 }