Getting the results of a Haskell script from Java

I'm trying to create a program to compare the amount of time it takes various haskell scripts to run, which will later be used to create graphs and displayed in a GUI. I've tried to create said GUI using Haskell libraries but I haven't had much luck, especially since I'm having trouble finding up to date GUI libraries for Windows. I've tried to use Java to get these results but either get errors returned or simply no result.

I've constructed a minimal example to show roughly what I'm doing at the moment:

    import java.io.*;
public class TestExec {
    public static void main(String[] args) {
        try {
            Process p = Runtime.getRuntime().exec("ghc test.hs 2 2");
            BufferedReader in = new BufferedReader(
                                new InputStreamReader(p.getInputStream()));
            String line = null;
            while ((line = in.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

And here is the Haskell script this is calling, in this case a simple addition:

test x y =  x + y

Currently there simply isn't any result stored or printed. Anyone have any ideas?