java map扩展

map集合被使用是因为具备映射关系。

一个学校有多个教室，每个教室都有多个学生。

public class Demo {
    public static void main(String[] args) {
        HashMap<String,HashMap<String,String>> czbk = new HashMap<String,HashMap<String,String>>();

        HashMap<String,String> yure = new HashMap<String,String>();
        yure.put("01","xiaoming");
        yure.put("02","xiaohong");

        HashMap<String,String> jiuye = new HashMap<String,String>();
        jiuye.put("01","xiaoxue");
        jiuye.put("02","xiaoli");

        czbk.put("jiuyeban",jiuye);
        czbk.put("yureban",yure);
        getInfo(czbk);
    }
    public static void getStudentInfo(HashMap<String ,String> roomMap){
        Iterator<String> it = roomMap.keySet().iterator();
       while (it.hasNext()){
           String id = it.next();
           String name = roomMap.get(id);
           System.out.println(id+":"+name);
       }
    }

    public static void getInfo(HashMap<String,HashMap<String,String>> school){
        Iterator<String> it = school.keySet().iterator();
        while (it.hasNext()){
            String roomName = it.next();
            HashMap<String,String> room = school.get(roomName);
            System.out.println(roomName);
            getStudentInfo(room);
        }
    }
}

class Student {
    private int id;
    private String name;

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

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name=‘" + name + ‘\‘‘ +
                ‘}‘;
    }
}

public class Demo {
    public static void main(String[] args) {
        HashMap<String, List<Student>> czbk = new HashMap<String, List<Student>>();

        List<Student> yure = new ArrayList<Student>();
        List<Student> jiuye = new ArrayList<Student>();

        czbk.put("yureban", yure);
        czbk.put("jiuyeban", jiuye);

        yure.add(new Student(1, "xiaohong"));
        yure.add(new Student(2, "xiaoli"));

        jiuye.add(new Student(1, "xiaoxue"));
        jiuye.add(new Student(2, "xiaomeng"));

        Iterator<String> it = czbk.keySet().iterator();
        while (it.hasNext()) {
            String roomName = it.next();
            List<Student> room = czbk.get(roomName);
            System.out.println(roomName);
            getInfos(room);
        }
    }

    public static void getInfos(List<Student> room) {
        Iterator<Student> it = room.iterator();
        while (it.hasNext()) {
            System.out.println(it.next());
        }
    }
}

原文地址：https://www.cnblogs.com/hongxiao2020/p/12661300.html