package ui;

/**
 * Created by nick on 10/22/15.
 */
public class RGBWindow {
}

package ui;

import javax.swing.*;

/**
 * Created by nick on 10/22/15.
 */
public class RGBWindow extends JFrame{


    public RGBWindow(){
        super("jrgb");
    }
}

Add constructor in RGBWindow