JavaSE-15.1.4【案例-HashSet集合存储学生对象并遍历】 

 1 package day6.lesson1;
 2 
 3 import java.util.HashSet;
 4 
 5 /*
 6 1.6 案例-HashSet集合存储学生对象并遍历
 7 
 8     创建一个存储学生对象的集合，存储多个学生对象，使用程序实现在控制台遍历该集合
 9     要求：学生对象的成员变量值相同，我们就认为是同一个对象
10 
11  */
12 public class HashSetDemo4 {
13     public static void main(String[] args) {
14         HashSet<Student> hs = new HashSet<>();
15 
16         Student s1 = new Student("tom", 22);
17         Student s2 = new Student("sam", 23);
18         Student s3 = new Student("amy", 21);
19         Student s4 = new Student("amy", 21);
20 
21         hs.add(s1);
22         hs.add(s2);
23         hs.add(s3);
24         hs.add(s4);
25 
26         for (Student s: hs){
27             System.out.println(s.getName() + "," + s.getAge());
28         }
29         /*
30         Student类重写equals()和hashCode()之前输出：
31         sam,23
32         amy,21
33         tom,22
34         amy,21
35 
36         为保证元素唯一性，Student类重写equals()和hashCode()两个方法（alt+insert自动生成）
37 
38         Student类重写equals()和hashCode()之后输出：
39         tom,22
40         amy,21
41         sam,23amy,21
42         sam,23
43          */
44     }
45 }

 

 1 package day6.lesson1;
 2 
 3 public class Student {
 4 
 5     private String name;
 6     private int age;
 7 
 8     public Student() {
 9     }
10 
11     public Student(String name, int age) {
12         this.name = name;
13         this.age = age;
14     }
15 
16     public void setName(String name) {
17         this.name = name;
18     }
19 
20     public void setAge(int age) {
21         this.age = age;
22     }
23 
24     public String getName() {
25         return name;
26     }
27 
28     public int getAge() {
29         return age;
30     }
31 
32     //HashDemo2.java
33     /*@Override
34     public int hashCode() {
35 //        return super.hashCode(); //默认
36         return 0; //此时可以实现让不同对象的哈希值相同
37     }*/
38 
39     //HashSetDemo4.java
40     @Override
41     public boolean equals(Object o) {
42         if (this == o) return true;
43         if (o == null || getClass() != o.getClass()) return false;
44 
45         Student student = (Student) o;
46 
47         if (age != student.age) return false;
48         return name != null ? name.equals(student.name) : student.name == null;
49     }
50 
51     @Override
52     public int hashCode() {
53         int result = name != null ? name.hashCode() : 0;
54         result = 31 * result + age;
55         return result;
56     }
57 }

 

posted @ 2021-05-31 21:40  yub4by  阅读(141)  评论(0)    收藏  举报