JAVA lang包介绍

import java.util.Objects;

public class Student extends Object {
    private int id; // 用于描述学号的成员变量
    private String name; // 用于描述姓名的成员变量

    public Student() {
    }

    public Student(int id, String name) {
        setId(id);
        setName(name);
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        if (id > 0) {
            this.id = id;
        } else {
            System.out.println("学号不合理哦！！！");
        }
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public boolean equals(Object obj) {
        if(this == obj) return  true;
        if(null==obj) return  false;
        if(obj instanceof Student){
            Student st=(Student) obj;
            System.out.println(st.id);
            System.out.println(id);
            return  st.getId()==this.getId();
        }
        return false;
    }


    @Override
    public int hashCode() {
        return getId(); // 不再代表内存地址的编号了
//        final int type = 12;
//        return type*31 + getName().hashCode();
    }

    @Override
    public String toString() {
        return "Student[id = " + getId() + ", name = " + getName() + "]";
    }


    public static  void  main(String[] args){
        Student s1=new Student(102,"zhangsan");
        Student s2=new Student(101,"zhangsan");
        System.out.println("s1 地址为： " + s1.id);
        System.out.println("s2 地址为： " + s2.id);
        System.out.println(s1 == s2);
        System.out.println(s1.equals(s2));
        System.out.println("---------------------------");
        Student s3=s1;
        System.out.println(s1.equals(s3));
        System.out.println("---------------------------");
        int hs = s1.hashCode();
        System.out.println("s1 的hascode:"+hs);
        String sto=s1.toString();
        System.out.println("s1 to string is "+sto);

    }
}