Ok, so I am setting up my own XML serialization (I know there are others out there, even some built in to Java, but I am doing it myself to learn and because it is so awesom
else what you can do (if you have limited number of classes).. you make a check of object by using 'instance of' operator and depending upon that place that in your arraylist
if(obj instance of abc)
ArrayList al = new ArrayList();