Make sure a generic parameter isn't a primitive

Question

I'm writing some code where I want to have a generic parameter, but it can't be a primitive. Is there a way to make sure a generic parameter to a function isn't a primitive?

For example, if I have the following function which checks if the parameter is an integer (using Integer because int doesn't have .getClass() ).:

public static final <E> int len(E e) {
    Integer i = 0;
    if (e.getClass() == i.getClass()) {
        throw new IllegalArgumentException();
    }
    return 0;
}

If I wanted to keep going for every primitive, this function would be very long (no pun intended). In essence, can I prevent a primitive object from being passed into a function with generic parameters?

Answer 1

It's never a primitive. If a primitive is passed in, it will be autoboxed to the appropriate wrapper class, eg int -> Integer .

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Regarding your statement int doesn't have .getClass() ...

Actually, int does have a class: int.class , but it is mainly used by the reflection api to represent method parameter types or return types of int .