HashMap存储自定义对象学习笔记

学生对象

public class Student implements Comparable<Student> {
    private String name;
    private int age;
    public Student() {
        super();

    }
    public Student(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "Student [name=" + name + ", age=" + age + "]";
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + age;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Student other = (Student) obj;
        if (age != other.age)
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }
    @Override
    public int compareTo(Student o) {
        int num = this.age - o.age;                 //以年龄为主要条件
        return num == 0 ? this.name.compareTo(o.name) : num;
    }
}

hasMap类

/*
     * * A:案例演示
     * HashMap集合键是Student值是String的案例
     * 键是学生对象,代表每一个学生
     * 值是字符串对象,代表学生归属地
     */
    public static void main(String[] args) {
        HashMap<Student, String> hm = new HashMap<>();
        hm.put(new Student("张三", 23), "北京");
        hm.put(new Student("张三", 23), "上海");
        hm.put(new Student("李四", 24), "广州");
        hm.put(new Student("王五", 25), "深圳");

        System.out.println(hm);
    }