Coding Kedua Java SE Di Ubuntu 12.04

ini lanjutan dari coding class yg sebelumnya, masih dalam 1 proyek yg sama:

/*
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package GUI2;

/**
 *
 * @author steven
 */

import javax.swing.*;
import java.awt.*;

public class WindowUtilities {
   
    public static void setNativeLookAndFeel(){
        try{
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        } catch(Exception e){
            System.out.println("Error Setting Native LAF: " + e);
           
       
        }
    }
   
    public static JFrame openInJFrame(Container content,
                                        int width,
                                        int height,
                                        String title,
                                        Color bgColor) {
       
        JFrame frame = new JFrame(title);
        frame.setBackground(bgColor);
        content.setBackground(bgColor);
        frame.setSize(width, height);
        frame.setContentPane(content);
        frame.addWindowListener(new ExitListener());
        frame.setVisible(true);
        return(frame);
       
    }
   
    public static JFrame openInJFrame(Container content,
                                        int width,
                                        int height,
                                        String title) {
       
        return(openInJFrame(content, width, height, title, Color.WHITE));
       
    }
   
   
        public static JFrame openInJFrame(Container content,
                                           int width,
                                           int height) {
           
           
            return(openInJFrame(content, width, height,
                                content.getClass().getName(),
                                Color.WHITE));
    }
}