HashMap集合练习之键是String值是Student

public class MapDemo01 {
    public static void main(String[] args) {
        //创建集合对象
        HashMap<String, Student> map = new HashMap<String, Student>();

        //创建学生对象
        Student s1 = new Student("aabb", 20);
        Student s2 = new Student("赤瞳", 21);
        Student s3 = new Student("dmh", 33);

        //添加元素到集合
        map.put("001", s1);
        map.put("002", s2);
        map.put("003", s3);

        //遍历集合（方式1：根据键 --> 值）
        //1.获取所有键的集合
        Set<String> keySet = map.keySet();
        //2.遍历所有键的集合
        for (String key : keySet) {
            //3.根据键找值
            Student s = map.get(key);
            System.out.println(key + "," + s.getName() + "," + s.getAge());
        }

        System.out.println("--------");

        //(方式2：根据键值对对象找键和值)
        //获取键值对对象
        Set<Map.Entry<String, Student>> entrySet = map.entrySet();
        //遍历键值对对象
        for (Map.Entry<String, Student> me : entrySet) {
            String key = me.getKey();
            Student value = me.getValue();
            System.out.println(key + "," + value.getName() + "," + value.getAge());
        }
    }
}

运行结果：