It seems like you're looking for a Java client to interact with the VNU Nu Html Checker API, specifically to download the vector product PNG.

You can use the vnu-jar package, which provides the Nu Html Checker «vnu.jar» file.

Here's a brief snippet in Java:

import java.io.File;
import java.io.IOException;

public class Main {
    public static void main(String[] args) throws IOException {
        File vnuFile = new File("path/to/vnu.jar");
        // Use the vnu.jar file to check your HTML
    }
}

Please note that you need to replace "path/to/vnu.jar" with the actual path where you downloaded the vnu.jar file.

If you're looking for a more specific Java client, I recommend checking out other packages on NPM Registry or exploring other options.