JButton NullPointerException problem

Question

Hi
I was wondering if you guys can help me out on this one. I'm been prompted with a NullPointerException whenever I click on either of the 2 buttons.
Thanks guys
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Alarm extends JPanel implements ActionListener{
    private JTextArea messageField;
    private JButton alarmOn, alarmOff;
    private JLabel alarmLED;
    public Alarm(){
        super.setPreferredSize(new Dimension(200,300));
        //configuring components;
        JButton alarmOn = new JButton("On");
        alarmOn.addActionListener(this);
        JButton alarmOff = new JButton("OFF");
        alarmOff.addActionListener(this);
        JLabel alarmLED = new JLabel("Alarm OFF");
        alarmLED.setOpaque(true);
        alarmLED.setBackground(Color.GREEN);
        messageField = new JTextArea(2,20);
        messageField.setEditable(false);
        messageField.setPreferredSize(new Dimension(200, 200));
        this.add(messageField, BorderLayout.PAGE_START);
        alarmOn.setPreferredSize(new Dimension(80, 20));
        this.add(alarmOn, BorderLayout.LINE_START);
        alarmOff.setPreferredSize(new Dimension(80, 20));
        this.add(alarmOff, BorderLayout.CENTER);
        alarmLED.setPreferredSize(new Dimension(65, 30));
        this.add(alarmLED, BorderLayout.LINE_END);
     public void actionPerformed(ActionEvent event){
        if(event.getSource()==this.alarmOn){
            this.alarmLED.setBackground(Color.RED);
            this.alarmLED.setText("Alarm ON");
        }else{
            this.alarmLED.setBackground(Color.GREEN);
            this.alarmLED.setText("Alarm OFF");
}//end of class;

Answer 1

I figured it out...I think i declared the button twice.
Funny...it seems easier to spot it in this forums comparing it on BlueJ
Will someone recommend me a better java client then BLueJ?
Preferably user friendly kinds
Thanks