Can someone please explain to me why this would cause a runtime exception? It seems to me like I'm accessing an arraylist of the type variable B exclusively.
class A {}
class B extends A {}
List<B> bL = new ArrayList<B>();
List<A> aL = bL;
aL.add(new A());
B b = bL.get(0); // runtime exception
You shouldn't have been able to compile your code successfully. You should be getting a compiler error at this line:
List<A> aL = bL;
because a List<Subclass> is not a List<Superclass>. That is disallowed specifically because of what you just attempted - insert a superclass instance into a list of subclass instances.
