Generics and class conversion

Question

I'm trying to generify old code, and there is some code where, given something like Integer.class, it returns Integer.TYPE (and vice-versa), and so on for the rest of the wrappers (if the input is not a wrapper, it returns the input class). This seems like a candidate for conversion (if it doesn't already exist somewhere). So, I have something like this:

public static <T> Class<T> convert(Class<T> type) {
    if (type == Integer.class) return Integer.TYPE;
    // and so on
    return type;
}

The problem with this code is that the compiler does not, by itself, know that in the if block we have ascertained that T == Integer, and thus does not know that returning Integer.TYPE is OK, thus barfing. Of course, we can always explicitly cast to Class<T>. The question is, is this cast safe, and thus I can be comfortable in adding the @SuppressWarnings("unchecked") annotation?

Answer 1

@SuppressWarnings("unchecked") should be fine here: we know each wrapper class W declares its TYPE field as a Class<W>, - probably just add a comment to explain that rational.

Note that Guava already has Primitives.unwrap to handle this for you, in case you're using it.