[newbie] NullPointerException when accessing ActionEvent handler

Code:

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ColorAction.java
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JPanel;

public class ColorAction implements ActionListener {

        public ColorAction (Color c)
        {
                backgroundColor = c;
        }
       
        public void actionPerformed(ActionEvent event) {
                       
                [B]buttonPanel.setBackground(backgroundColor);[/B]
//breaks here
        }
       
        private Color backgroundColor;
        private JPanel buttonPanel;

}

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

public class ButtonFrame extends JFrame {
       
        public ButtonFrame() {
                setTitle("ButtonTest");
                setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
               
                //create buttons
                JButton yellowButton = new JButton("Yellow");
                JButton blueButton = new JButton("Blue");
                JButton redButton = new JButton("Red");
               
                JPanel buttonPanel = new JPanel();
               
                //add buttons to panel
                buttonPanel.add(yellowButton);
                buttonPanel.add(blueButton);
                buttonPanel.add(redButton);
               
                //add panel to frame
                add(buttonPanel);
               
                //create button Actions
                ColorAction yellowAction = new ColorAction(Color.yellow);
                ColorAction blueAction = new ColorAction(Color.blue);
                ColorAction redAction = new ColorAction(Color.red);
               
                //associate actions with buttons
                yellowButton.addActionListener(yellowAction);
                blueButton.addActionListener(blueAction);
                redButton.addActionListener(redAction);
        }
               
                private static final int DEFAULT_WIDTH=300;
                private static final int DEFAULT_HEIGHT=200;
}


Test.java
import java.awt.EventQueue;

import javax.swing.JFrame;

public class Test {

        /**
        * @param args
        */
        public static void main(String[] args) {
                EventQueue.invokeLater(new Runnable()
                        {
                                public void run()
                                {        //FIX Does not work!!
                                        ButtonFrame frame = new ButtonFrame();
                                        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                                        frame.setVisible(true);
                                }
                        }
                );

        }

}

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:confused:

I tried creating a similar interface in NetBeans so that I can try to compare side-by-side, however, somehow the UI elements don't show up when running Java Projects. I noted that the code breaks at this point though:

Code:

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...
 private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
        backgroundPanel.setBackground(Color.yellow);
  //cannot be references from a static context.
    }

I think NetBeans has a different style of connecting events.
...

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