Re: Help with an arraylist of subclass using generics

From:

Lew <lew@lewscanon.com>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 21 May 2009 11:57:18 -0700 (PDT)

Message-ID:

<610d0d6f-d86d-4ea1-95f8-3b83d5e4bb55@q14g2000vbn.googlegroups.com>

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 !

//START CODE
...
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
Iterator<RicDataElement>.

if(iter1.next() instanceof RicDat=

aCrossElement){

else if(iter1.next() instanceof R=

icDataTassiElement){

else if(iter1.next() instanceof RicDa=

taUpdElement){

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

--
Lew