java - 为什么我不断往 hashMap 中放入东西后，它一直说 hashMap 的大小为零？

Question

我想做的是使用addRoom()将房间添加到 HashMap 中(我不想重复)。然后，我使用 getRoom(String) 或 getRooms() 将它们传递给 Controller ​​。

问题是，正如您在我的多个 System.out.prints 中看到的那样，无论我运行 addRoom() 多少次，大小都保持在 0 >。

我做错了什么还是程序中的其他地方有问题？

package calendar;

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

public class Building {

    String buildingName = null;

    private Map<String, Classroom> rooms =
        new HashMap<String, Classroom>();

    public Building() {
    }
    public Building(String name){
        buildingName=name;
    }

    /**
     * @return the rooms
     */
    public Map<String, Classroom> getRooms() {
        System.out.println("room size from building.java:" +
            rooms.size());
        return rooms;
    }

    public Classroom getRoom(String roomName) {
        if (rooms.containsKey(roomName)) {
            return rooms.get(roomName);
        }
        return new Classroom("null");
    }

    /**
     * @param rooms the rooms to set
     */
    public void setRooms(Map<String, Classroom> rooms) {
        this.rooms = rooms;
    }

    public void addRoom(String roomNumber) {
        System.out.println("Room added: "+roomNumber +" to "+ 
            buildingName+ " size:"+rooms.size());
        rooms.put(roomNumber, new Classroom(roomNumber));
    }
}

我从解析器调用此方法，因此代码有点冗长，但我会减少它并尝试仅粘贴相关部分:

private Map<String, Building> currentBuilding = new HashMap<String, Building>();

现在这是一个 for 循环，它遍历需要解析的所有数据 block : currentBuilding.put(建筑物, 新建筑物(建筑物)); currentBuilding.get(building).addRoom(room);

其中建筑物和房间是字符串。建筑物按其应有的方式启动。显然我希望每个建筑物的房间都在其相应的建筑物中，但这似乎并没有按预期发生。

Answer 1

你的类(class)运行得很好!刚刚做了一些修复

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

public class Building {

 String buildingName = null;
 private static Map<String, Classroom> rooms =
        new HashMap<String, Classroom>();

 public Building() {
 }

 public Building(String name) {
    buildingName = name;
 }

 /**
  * @return the rooms
  */
 public Map<String, Classroom> getRooms() {
    System.out.println("room size from building.java:"
            + rooms.size()); 
    return rooms;
 }

 public Classroom getRoom(String roomName) {
    if (rooms.containsKey(roomName)) {
        return rooms.get(roomName);
    }
    return new Classroom("null");
 }

 /**
  * @param rooms the rooms to set
  */
 public void setRooms(Map<String, Classroom> rooms) {
    this.rooms = rooms; // did you use this method to initialize map?
 }

 public void addRoom(String roomNumber) {
    rooms.put(roomNumber, new Classroom(roomNumber));
    System.out.println("Room added: " + roomNumber + " to "
            + buildingName + " size:" + rooms.size()); // print info after action
 }
}

和用法

    public static void main(String[] args) {
        Building building = new Building("first building");
        building.addRoom("1"); // add room 1
        building.addRoom("2"); // add room 2
        building.addRoom("3"); // add room 3
        System.out.println(building.getRooms().size()); 
    }

输出

Room added: 1 to first building size:1
Room added: 2 to first building size:2
Room added: 3 to first building size:3
room size from building.java:3
3

尽管如此，您的类按预期工作，问题可能出在类使用中，您如何处理对 Building 类的引用，可能您希望它是静态的？