Use of HashMap collection

Create the Student class

package com.sean.base.mapStudy;

/**
 * 
 * @create 2021-02-26 9:01
 */
public class Student {
    
    
    private  String name;
    private  int stuNo;

    public Student(String name, int stuNo) {
    
    
        this.name = name;
        this.stuNo = stuNo;
    }

    public String getName() {
    
    
        return name;
    }

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

    public int getStuNo() {
    
    
        return stuNo;
    }

    public void setStuNo(int stuNo) {
    
    
        this.stuNo = stuNo;
    }

    @Override
    public String toString() {
    
    
        return "Student{" +
                "name='" + name + '\'' +
                ", stuNo=" + stuNo +
                '}';
    }
}

package com.sean.base.mapStudy;

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

/**
 * HashMap集合的使用
 * 存储结构：哈希表（数组+链表+红黑树）
 * 使用key和hashcod和equals作为重复
 * @create 2021-02-26 9:00
 */
public class Demo02 {
    
    
    public static void main(String[] args) {
    
    
        //创建集合
        HashMap<Student, String> students = new HashMap<Student, String>();
        //添加元素
        Student s1 = new Student("孙悟空",100);
        Student s2 = new Student("猪八戒",101);
        Student s3 = new Student("白龙马",102);
        students.put(s1,"北京");
        students.put(s2,"上海");
        students.put(s3,"杭州");
        System.out.println("元素个数："+students.size());
        System.out.println(students.toString());

        //2删除操作
        /*students.remove(s1);
        System.out.println("删除之后："+students.size());*/
        //3遍历
        //3.1使用keySet
        System.out.println("-------使用keySet-------");
        for (Student key:students.keySet()
        ) {
    
    
            System.out.println(key.toString()+"----------"+students.get(key));

        }
        //3.2使用entrySet
        System.out.println("-------3.2使用entrySet-------");
        for (Map.Entry<Student,String> entry:students.entrySet()
        ) {
    
    
            System.out.println(entry.getKey()+"-------"+entry.getValue());

        }
        //4判断
        System.out.println(students.containsKey(s1));
        System.out.println(students.containsValue("杭州"));
    }
}