map集合存儲實體類--遍歷

java源碼示例展示：

package map;

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;

/**
 * 使用linkedhashmap 效果最好  
 * 存儲學生對象，還要輸出  使用 遍歷輸出
 * @author superdrew
 */
public class TestMapStudent {
    public static void main(String[] args) {
        //創建 存儲stu的 map   key 是 int id  value 是具體的每一個學生
        Map<Integer,Student> stuMap = new LinkedHashMap<Integer,Student>();
        //創建學生對象 
        Student stu1 = new Student(1001, "Drew", 89, 21);
        Student stu2 = new Student(2002, "SuperDrew", 99, 20);
        Student stu3 = new Student(3003, "Lily", 100, 25);
        Student stu4 = new Student(4004, "Mark", 78, 22);
        Student stu5 = new Student(5005, "Bob", 88, 21);
        
        //把學生對象放入 到 map集合
        stuMap.put(stu1.getId(), stu1);
        stuMap.put(stu2.getId(), stu2);
        stuMap.put(stu3.getId(), stu3);
        stuMap.put(stu4.getId(), stu4);
        stuMap.put(stu5.getId(), stu5);
        
        //根據輸入的具體學號 返回一個具體的學生信息
        @SuppressWarnings("resource")
        Scanner sc = new Scanner(System.in);
        System.out.println("請輸入要查找的學號:");
        int id = sc.nextInt();
        Student  stuObject = stuMap.get(id);
        System.out.println(stuObject);
        
        
        //遍歷map集合輸出---錯誤提示：map集合的三種遍歷輸出方式，請看我的上一篇blogs。
        /*for(int i=1;i<=stuMap.size();i++){  
            System.out.println(stuMap.get(i));
        }*/
        /*小結：輸出全部為NULL，說明遍歷map集合的時候不能簡單的使用for i遍歷。*/
        
        
        //獲取 stuMap所有的key
        System.out.println("所有的學生信息如下：");
        Set<Integer> stuSet = stuMap.keySet();
        for(int stuId:stuSet){
            System.out.println(stuMap.get(stuId));
        }
    }
}

實體類Student.java：

package map;
/**
 * 學生類
 * @author superdrew
 *
 */
public class Student {
    private int id;
    private String name;
    private double score;
    private int age;
    
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public double getScore() {
        return score;
    }
    public void setScore(double score) {
        this.score = score;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    
    public Student(int id, String name, double score, int age) {
        super();
        this.id = id;
        this.name = name;
        this.score = score;
        this.age = age;
    }
    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", score=" + score + ", age=" + age + "]";
    }
}

結果展示：