Java - 使 HashMap 可从其他类使用的问题

Question

为了解决当前问题，我进行了很多研究，但是，我不确定出了什么问题:

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

    public class Items
    {
      public static void main (String args[])
      {
      HashMap<String, Double> Hallway = new HashMap<String, Double>();
      HashMap<String, Double> Toilet = new HashMap<String, Double>();
      HashMap<String, Double> ChemistryLab = new HashMap<String, Double>();
      HashMap<String, Double> Outdoors = new HashMap<String, Double>();
      HashMap<String, Double> Library = new HashMap<String, Double>();
      HashMap<String, Double> Engineering = new HashMap<String, Double>();
      HashMap<String, Double> Cafeteria = new HashMap<String, Double>();
      HashMap<String, Double> ComputerLab = new HashMap<String, Double>();
      HashMap<String, Double> LectureTheater = new HashMap<String, Double>();
      HashMap<String, Double> MedicalCentre = new HashMap<String, Double>();
      }

    public HashMap<String, Double> getHallwayItems() 
    {
      return Hallway;        
    }

    public HashMap<String, Double> getToiletItems() 
    {
      return Toilet;
    }

    public HashMap<String, Double> getChemistryLabItems() 
    {
     return ChemistryLab;
    }

    public HashMap<String, Double> getOutdoorItems() 
    {
     return Outdoors;
    }

    public HashMap<String, Double> getLibraryItems() 
    {
     return Library;
    }

    public HashMap<String, Double> getEngineeringItems() 
    {
     return Engineering;
    }

    public HashMap<String, Double> getCafeteriaItems() 
    {
     return Cafeteria;
    }

    public HashMap<String, Double> getComputerLabItems() 
    {
     return ComputerLab;
    }

    public HashMap<String, Double> getLectureTheaterItems() 
    {
     return LectureTheater;
    }

    public HashMap<String, Double> getMedicalCentreItems() 
    {
     return MedicalCentre;
    }

    }

它说当我尝试编译时找不到变量 Hallway，但是我不知道如何解决这个问题。感谢您提供的任何帮助。

Answer 1

Hallway 是 main 函数内的局部变量。 main 也是一个静态函数。这些在 main 中声明的变量不能被其他函数访问。

有两种选择，

1) 将所有 map 声明为对象的静态成员，并具有 static getHallway() static getToilet 等。2)我个人建议这样做，

导入java.util.Map;导入java.util.HashMap;

public class Items
{
    private HashMap<String, Double> Hallway = new HashMap<String, Double>();
    private HashMap<String, Double> Toilet = new HashMap<String, Double>();
    ...

    public HashMap<String, Double> getHallwayItems() 
    {
       return Hallway;        
    }
    ...
    ...

    public static void main (String args[])
    {
        Items myItem = new Items();
         myItem.getHallwayItems(); // and do whatever you want.
    }
}

这样，我们也可以利用 OOPS...