Casting to generic type in Java doesn't raise ClassCastException?

Question

I have come across a strange behavior of Java that seems like a bug. Is it? Casting an Object to a generic type (say, K) does not throw a ClassCastExcepti

Answer 1

Java generics use type erasure, meaning those parameterized types aren't retained at runtime so this is perfectly legal:

List list = new ArrayList();
list.put("abcd");
List list2 = (List)list;
list2.add(3);

because the compiled bytecode looks more like this:

List list = new ArrayList();
list.put("abcd");
List list2 = list;
list2.add(3); // auto-boxed to new Integer(3)

Java generics are simply syntactic sugar on casting Objects.