Why can't use Void as the return type for main method

Question

So I wanted to test Void type then I wrote this simple program :

package ehsan;

public class NumTest {
    public static Void main(String[] args) {
        System.out.println("Hello, World!");
        return null; /* The compiler forced me to do so. I just can't realize what is the point in returning in Void type!? */
    }
}

So now when I want to compile, the compiler complains :

main method must return a value of type void

Why can't the compiler see that I'm returning nothing and am using Void?

Answer 1

You should use void (lowercase v) not Void object. Void object is not going to get autoboxing like e.g. int/Integer, see Java Language Specification for a list of autoboxing objects.

Void is not a wrapper for void, it is just an object that has a very similar name so it can be used in places where you need to specify a return type (like e.g. Callable<T>), it is just for documentation purposes and to workaround some generic classes return types.

Second use case is in reflection (when you want to check the return value of a void function, you will get Void.TYPE).

Correct line is:

public static void main(String[] args)