Java Basics (three) override equals and hashCode

import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Objects;
import java.util.Set;

public class test_20190924 {
    public static void main(String[] ins) {
        JavaBean o = new JavaBean();
        o.id = "1";
        o.name = "JavaBean";
        JavaBean b = new JavaBean();
        b.id = "1";
        b.name = "JavaBean";
        Set<JavaBean> set = new HashSet<>();// 不能重复 无序
        set.add(o);
        set.add(b);
        System.out.println(set.size());
        List<JavaBean> list = new ArrayList<>();// 可以重复 有序
        list.add(o);
        list.add(b);
        System.out.println(list.size());
        System.out.println(b.equals(o));
        System.out.println(b.hashCode());
        System.out.println(o.hashCode());
        System.out.println(b == o);
        System.out.println(b);

    }

}

class JavaBean {

    String id;
    String name;

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        JavaBean b = (JavaBean) o;
        return Objects.equals(id, b.id) && Objects.equals(name, b.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id, name);
    }

    @Override
    public String toString() {
        return "{\"id\":\"" + id + "\",\"name\":\"" + name + "\"}";
    }

}