Java~HashMap的遍歷

package org.nico.ratel.landlords.helper.TestMap;

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

class Room {
    int room_id;

    public Room(int room_id) {
        this.room_id = room_id;
    }

    @Override
    public String toString() {
        return "Room{" +
                "room_id=" + room_id +
                '}';
    }
}

public class Main {
    public static void main(String[] args) {
        Map<Integer, Room> m = new HashMap<>();

        m.put(1, new Room(11));
        m.put(2, new Room(22));

        for (Integer key : m.keySet()) {
            Room r = m.get(key);
            System.out.println(r);
        }

        System.out.println("刪除後---");
        m.remove(1);

        // 遍歷這個的key和m存儲的key類型一致
        for (Integer key : m.keySet()) {
            Room r = m.get(key);
            System.out.println(r);
        }
    }
}

/*
Room{room_id=11}
Room{room_id=22}
刪除後---
Room{room_id=22}
 */