HashMap集合存储学生对象并遍历

Posted 2023-03-31 iuiu啊

需求：创建一个HashMap集合，键是学生对象（Student）,值是居住地。存储多个键值对元素，并遍历。

        要求保证键的唯一性：如果学生对象的成员变量值相同，我们就认为是同一个对象

思路：

        定义学生类

        创建HashMap集合对象

        创建学生对象

        把学生添加到集合

        遍历集合

        在学生类中重写两个方法

                hashCode()

                equals()

代码实现：

        编写Student类

package com.aynu3;

import java.util.Objects;

public class Student 
    private String name;
    private int age;

    public Student() 
    

    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;
    

    @Override
    public boolean equals(Object o) 
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Student student = (Student) o;

        if (age != student.age) return false;
        return Objects.equals(name, student.name);
    

    @Override
    public int hashCode() 
        int result = name != null ? name.hashCode() : 0;
        result = 31 * result + age;
        return result;
    

package com.aynu3;

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

public class HashMapDemo 
    public static void main(String[] args) 

        //创建HashMap集合对象
        HashMap<Student,String> hm=new HashMap<Student,String>();

        //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);
        Student s4=new Student("王祖贤",33);

        //把学生添加到集合
        hm.put(s1,"西安");
        hm.put(s2,"武汉");
        hm.put(s3,"洛阳");
        hm.put(s4,"北京");

        //遍历集合
        Set<Student> keySet = hm.keySet();
        for (Student key:keySet) 
            String value = hm.get(key);
            System.out.println(key.getName() + "," + key.getAge()+","+value);
        
    

运行结果：

王祖贤,33,北京
张曼玉,35,武汉
林青霞,30,西安 

JavaSE-14.2.2案例-List集合存储学生对象并遍历

package day5.lesson2;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/*
2.3 案例-List集合存储学生对象并遍历
    创建一个存储学生对象的集合，存储3个学生对象，使用程序实现在控制台遍历该集合
 */
public class ListDemo2 {
    public static void main(String[] args) {
        List<Student> list = new ArrayList<>();

        Student s1 = new Student("sam", 12);
        Student s2 = new Student("amy", 11);
        Student s3 = new Student("tom", 12);

        list.add(s1);
        list.add(s2);
        list.add(s3);

        //遍历方式1
        Iterator<Student> it = list.iterator();
        while (it.hasNext()){
            Student s = it.next();
            System.out.println(s.getName() + "," + s.getAge());
        }

        //遍历方式2
        for(int i=0; i<list.size(); i++){
            Student stu = list.get(i);
            System.out.println(stu.getName() + "," + stu.getAge());
        }

    }
}

　　

package day5.lesson2;

public class Student {

    private String name;
    private int age;

    public Student() {
    }

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

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

    public void setAge(int age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }
}