What are the risks of explicitly casting from a list of type List<? extends MyObject> to a list of type List in Java?

Question

I think the title should explain it all but just in case...

I want to know what risks and potential issues relating to casting can arise from the following snippet o

Answer 1

Consider you do something like:

List childClassList = new ArrayList();
childClassList.add(childClassOneInstanceOne);
childClassList.add(childClassOneInstanceTwo);

List wildcardList = childClasslist; // works fine - imagine that you get this from a method that only returns List
List typedList = (List) wildcardList; // warning

typedList.add(childClassTwoInstanceOne); // oops my childClassList now contains a childClassTwo instance
ChildClassOne a = childClassList.get(2); // ClassCastException - can't cast ChildClassTwo to ChildClassOne

This is the only major problem. But if you only read from your list it should be ok.