Java基础知识（三）重写equals和hashCode

1import java.text.MessageFormat;
2import java.util.ArrayList;
3import java.util.HashSet;
4import java.util.List;
5import java.util.Objects;
6import java.util.Set;
7
8public class test_20190924 {
9    public static void main(String[] ins) {
10        JavaBean o = new JavaBean();
11        o.id = "1";
12        o.name = "JavaBean";
13        JavaBean b = new JavaBean();
14        b.id = "1";
15        b.name = "JavaBean";
16        Set<JavaBean> set = new HashSet<>();// 不能重复 无序
17        set.add(o);
18        set.add(b);
19        System.out.println(set.size());
20        List<JavaBean> list = new ArrayList<>();// 可以重复 有序
21        list.add(o);
22        list.add(b);
23        System.out.println(list.size());
24        System.out.println(b.equals(o));
25        System.out.println(b.hashCode());
26        System.out.println(o.hashCode());
27        System.out.println(b == o);
28        System.out.println(b);
29
30    }
31
32}
33
34class JavaBean {
35
36    String id;
37    String name;
38
39    @Override
40    public boolean equals(Object o) {
41        if (this == o) {
42            return true;
43        }
44        if (o == null || getClass() != o.getClass()) {
45            return false;
46        }
47        JavaBean b = (JavaBean) o;
48        return Objects.equals(id, b.id) && Objects.equals(name, b.name);
49    }
50
51    @Override
52    public int hashCode() {
53        return Objects.hash(id, name);
54    }
55
56    @Override
57    public String toString() {
58        return "{\"id\":\"" + id + "\",\"name\":\"" + name + "\"}";
59    }
60
61}