String值是Student_string s=”student”-优快云博客

本文链接：https://blog.youkuaiyun.com/wenwenkaii/article/details/117380781

这个示例展示了如何在Java中使用HashMap存储键值对并进行遍历。在MapDemo01和MapDemo02类中，分别通过keySet()方法和entrySet()方法遍历键值对，并打印出来。在HashMapDemo类中，创建了一个HashMap，键为学号，值为Student对象，展示了两种遍历方式：通过键找值和通过键值对找键和值。

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package itheima_02;

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

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

        //添加元素
        map.put("张无忌", "赵敏");
        map.put("郭靖", "黄蓉");
        map.put("杨过", "小龙女");

        //获取所有键的集合,用keySet()方法实现
        Set<String> keySet = map.keySet();
        //遍历键的集合,获取到每一个键,用增强for实现
        for (String key : keySet){
            String value = map.get(key);
            System.out.println(key + "," + value);
        }

    }
}

package itheima_02;

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

public class MapDemo02 {
    public static void main(String[] args) {
        //创建集合对象
        Map<String, String> map = new HashMap<String, String>();

        //添加元素
        map.put("张无忌", "赵敏");
        map.put("郭靖", "黄蓉");
        map.put("杨过", "小龙女");

        Set<Map.Entry<String, String>> entrySet = map.entrySet();
        //遍历键值对对象的集合，得到每一个键值对对象
        for (Map.Entry<String, String> me : entrySet){
            //根据键值对对象获取键和值
            String key = me.getKey();
            String value = me.getValue();
            System.out.println(key + "," + value);
        }
    }
}

package itheima_03;
/*

   需求:
       创建一个HashMap集合, 键是学号(String),值是学生对象(String)。存储三个键值对元素,并遍历

   思路:
      1:定义学生类
      2:创建HashMap集合对象
      3:创建学生对象
      4:把学生添加到集合
      5:遍历集合
          方式1:键找值
          方式2:键值找对象找键和值
*/

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

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

        //创建学生对象
        Student s1 = new Student("林青霞", 30);
        Student s2 = new Student("张曼玉", 35);
        Student s3 = new Student("王祖贤", 33);

        //把学生添加到集合
        hm.put("itheima001", s1);
        hm.put("itheima002", s2);
        hm.put("itheima003", s3);

        //方式1：键找值
        Set<String> keySet = hm.keySet();
        for (String key : keySet) {
            Student value = hm.get(key);
            System.out.println(key + "," + value.getName() + "," + value.getAge());
        }
        System.out.println("--------");

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

package itheima_03;

public class Student {
    private  String name;
    private int age;

    public Student(String name, int age) {
        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;
    }
}