/**
     * * A:案例演示
     * 集合嵌套之HashMap嵌套HashMap
     * 
     * 需求:
     * 雙元課堂有很多基礎班
     * 第88期基礎班定義成一個雙列集合,鍵是學生對象,值是學生的歸屬地
     * 第99期基礎班定義成一個雙列集合,鍵是學生對象,值是學生的歸屬地
     * 
     * 無論88期還是99期都是班級對象,所以為了便於統一管理,把這些班級對象添加到雙元課堂集合中
     */
    public static void main(String[] args) {
        //定義88期基礎班
        HashMap<Student, String> hm88 = new HashMap<>();
        hm88.put(new Student("張三", 23), "北京");
        hm88.put(new Student("李四", 24), "北京");
        hm88.put(new Student("王五", 25), "上海");
        hm88.put(new Student("趙六", 26), "廣州");

        //定義99期基礎班
        HashMap<Student, String> hm99 = new HashMap<>();
        hm99.put(new Student("年輕帶", 1023), "北京");
        hm99.put(new Student("老年代",1024), "北京");
        hm99.put(new Student("持久帶",1025), "上海");
        hm99.put(new Student("伊甸園",1026), "廣州");

        //定義雙元課堂
        HashMap<HashMap<Student, String>, String> hm = new HashMap<>();
        hm.put(hm88, "jvm區域");
        hm.put(hm99, "java學院區");

        //遍歷雙列集合
        for(HashMap<Student, String> h : hm.keySet()) {     //hm.keySet()代表的是雙列集合中鍵的集合
            String value = hm.get(h);                       //get(h)根據鍵對象獲取值對象
            //遍歷鍵的雙列集合對象
            for(Student key : h.keySet()) {                 //h.keySet()獲取集合總所有的學生鍵對象
                String value2 = h.get(key);

                System.out.println(key + "=" + value2 + "=" + value);
            }
        }

    }
 

bean對象

public class Student implements Comparable<Student> {
    private String name;
    private int age;
    public Student() {
        super();

    }
    public Student(String name, int age) {
        super();
        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 String toString() {
        return "Student [name=" + name + ", age=" + age + "]";
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + age;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Student other = (Student) obj;
        if (age != other.age)
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }
    @Override
    public int compareTo(Student o) {
        int num = this.age - o.age;                 //以年齡為主要條件
        return num == 0 ? this.name.compareTo(o.name) : num;
    }
}
 

集合嵌套之HashMap嵌套HashMap學習筆記