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Keeping a reference to a list

Posted on 2007-11-29
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Last Modified: 2010-03-30
Hi,

I have some class that loads an array list. I want to let another class instance reference it, but don't want to make a whole copy of it. Something like:

class Loader {
    public void Load()
    {
         m_List.add(new something());
    }
    ArrayList<something> m_List;
}

class Other {

     public void SetListReference(ArrayList<something> theList)
     {
           // just want to keep a reference to theList here.
          m_ListRef = theList;
     }
     ArrayList<something>& m_ListRef;
}


Something like that,

Thanks
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Question by:DJ_AM_Juicebox
  • 2
3 Comments
 
LVL 17

Accepted Solution

by:
contactkarthi earned 500 total points
ID: 20374426
try something like this
class Loader {
    public void Load()
    {
         m_List.add(new something());
    }
    ArrayList<something> m_List;
    
    public ArrayList<something> getListReference()
    {
		return m_List;
	}
    
}
 
class Other {
 
     public void SetListReference(ArrayList<something> theList)
     {
           // just want to keep a reference to theList here.
          m_ListRef = theList;
     }
     ArrayList<something>& m_ListRef;
     
     public static void main(String args[])
     {
		 Other oth = new Other();
		 
		 Loader loader = new loader();
		 loader.Load();
		 
		 oth.SetListReference(loader.getListReference());
	}
}

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Expert Comment

by:dankuck
ID: 20374497
In Java, all object variables are references.

The code you have supplied would work if you remove the C++ ampersand:

ArrayList<something>& m_ListRef;

becomes

ArrayList<something> m_ListRef;

The code in SetListReference will not copy the ArrayList elements into a new ArrayList, it will just put the original ArrayList reference into the new variable m_ListRef.  Then any changes you make to the ArrayList within class Other will be reflected when class Loader uses the ArrayList.
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LVL 1

Expert Comment

by:dankuck
ID: 20383922
You'll need to remove the & on contactkarthi's line 22.
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