Question

我已经研究了很多关于当前问题的答案，但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;
    }

    }

它说我在尝试编译时找不到变量Hallway，但是我看不出这是如何解决的。感谢您提供的任何帮助。

Answer 1

您需要将Hallway和其他人定义为实例变量。变量在方法范围内定义，在其他方法中无法访问。

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

public class Items
{
  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 static void main (String args[])
  {

  }

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;
}

}

Answer 2

Hallway是main函数中的局部变量。而且主要是静态功能。在main内声明的这些变量不能从其他函数访问。

有两种选择，

1）将所有地图声明为对象的静态成员，并具有静态getHallway()静态getToilet等。 2）我个人会建议这个，

import java.util.Map; import 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，我们也开发了OOPS ...

Java - 使其他类可以使用HashMap的问题

2 个答案: