Difference between Class and Class<?>

Question

What is the difference between a Class and a Class declaration.

• Class a;
• Class b;

Answer 1

"it look like old code or code written by someone who hasn't learned generics yet." This is an correct statement. Class (pronounced "class of unknown"), that is, a class whose type matches anything. It's called a wild-card type for obvious reasons.

for example:

public void drawAll(List shapes) {
    for (Shape s: shapes) {
        s.draw(this);
   }
}

type rules say that drawAll() can only be called on lists of exactly Shape: it cannot, for instance, be called on, say, a List. That is unfortunate, since all the method does is read shapes from the list, so it could just as well be called on a List.

What we really want is for the method to accept a list of any kind of shape.

public void drawAll (List  shapes) {

}

read more: http://docs.oracle.com/javase/tutorial/extra/generics/wildcards.html