Re: Help with an arraylist of subclass using generics

Lew <>
Thu, 21 May 2009 11:57:18 -0700 (PDT)
Alessandro wrote:

I have a static ArrayList "buffer" with many objects. All of them
belongs to 3 classes (RicDataCrossElement, RicDataTassiElement,
RicDataUpdElement) which are childs of RicDataElement class.

I need to extract every object from this list and do some actions
according to the different class.
I have errors in the following code, please could you help ?

Of course I'm also doing more and more "next()" and every time I'm
passing to the following item ... so that's wrong !

public static ArrayList<RicDataElement> buffer;
Iterator<? extends RicDataElement> iter1 = buffer.iterator();
          while (iter1.hasNext())

You really, really need to use gentler indentation. Four spaces per
level is about the maximum Usenet can take.

Iterator<? extends RicDataElement> means that the Iterator is over
elements all of the same type, that singular type being a subtype of
RicDataElement. It does not mean that some items in the Iterable are
of one subtype and some of another. That would be an

                    if( instanceof RicDat=


                    else if( instanceof R=


                  else if( instanceof RicDa=


As others have mentioned, the presence of the 'instanceof' test
indicates that you have severely misused object orientation.


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