Java- So evil, yet so sublime...?

So, I have a ton of homework to do, as usual. I am doing fine in writing and calculus, but am practically failing my Data Structures and Algorithms Java class and have like a 'C' in Discrete Math. Anyhow, instead of doing that homework, yet again as usual, I spent my time programming useless things for my own personal uses and reasons. My latest? A Java GUI that will close your music player for you after a specified amount of time (in minutes). I was just so proud of it that I thought I would post the source code (works with Rhythmbox in Ubuntu, but easily alterable to any OS):


package rhythmBox;

import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.util.concurrent.TimeUnit;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class closeRhythmBox extends JFrame implements ActionListener {

private static final long serialVersionUID = 1L;

private static final int WIDTH = 400;
private static final int HEIGHT = 300;

private JTextField minutesBox;

public static void main(String[] args) {
new closeRhythmBox().setVisible(true);
}

public static void execKill(long minutes) throws InterruptedException {
Thread.sleep(minutes*60*1000);
try{
Runtime.getRuntime().exec("pkill rhythmbox");
System.exit(0);
}
catch (IOException ioe) {
         ioe.printStackTrace();
       }
}
public closeRhythmBox(){
setTitle("Rythmbox Timer");
setSize(WIDTH, HEIGHT);
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

Container pane = getContentPane();
pane.setLayout(new FlowLayout());

JPanel box = new JPanel();
box.setLayout(new FlowLayout());
JButton startButton = new JButton("Start");
startButton.addActionListener(this);
box.add(startButton);
box.add(new JLabel("Minutes Until Close"));
box.add(minutesBox = new JTextField(20));

pane.add(box);
pack();

}

public void actionPerformed(ActionEvent e) {
String textNum = minutesBox.getText();
long minuteNum = Long.parseLong(textNum);
if (e.getActionCommand().equals("Start")){
try {
execKill(minuteNum);
} catch (InterruptedException e1) {
e1.printStackTrace();
}
}
}
}