Unexpected width of a JPanel

Question

Hi,
Yesterday I had a problem with a Traffic Light I am creating, as a part of a bigger project. I got helped (thanks for the help), and that problem is solved. Today I noticed something else. The construction I use is a JPanel, containing a button above a traffic light. The button contains a customer name. Under this button, the traffic light displays the severity of a customer problem. What I noticed is that the space to the right of the button is bigger than the space to the left of the button. This problem does not exist when I use a Gridlayout. I use the Boxlayout so the button does not get the same size as the lights of the traffic lights. Does anyone know what I can do to get that space to the right of the button away?
The code (which should compile and run without a problem) I use is:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
* Temporary class to be loaded into the TlsFrame for testing purposes
public class TrafficLight extends JPanel
                          implements ActionListener {
     private Border raisedBevel;
     private JButton tlsButton;
     private JComponent component;
     private TlsLight redLight;
     private TlsLight yellowLight;
     private TlsLight greenLight;
     private String name;
     private String problemLevel;
     private boolean isNewProblem;
     public TrafficLight (String theName, String theProblemLevel, boolean theNewProblem) {
          name = theName;
          problemLevel = theProblemLevel;
          isNewProblem = theNewProblem;
          // Create the borders
          raisedBevel = BorderFactory.createRaisedBevelBorder();
          setUp();
      * Places all items on this Panel.
     private void setUp() {
          component = createComponent();
          add(component);
          if (isNewProblem)
              component.setBackground(Color.GRAY);
          else
              component.setBackground(Color.BLACK);
          setVisible (true);
     private JComponent createComponent () {
          // JPanel panel = new JPanel( new GridLayout(4, 1) );
          JPanel panel = new JPanel ();
          panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
          panel.setBorder(raisedBevel);
          // Create the button containing the Customer name
          tlsButton = new JButton(name);
          tlsButton.setActionCommand(name);
          tlsButton.addActionListener(this);
          panel.add(tlsButton);
          // Create the lights
          boolean isOn = true;
          boolean isNewProblem = true;
          redLight = new TlsLight (Color.RED, isOn, isNewProblem);
          panel.add(redLight);
          yellowLight = new TlsLight (Color.YELLOW, !isOn, isNewProblem);
          panel.add(yellowLight);
          greenLight = new TlsLight (Color.GREEN, isOn, !isNewProblem);
          panel.add(greenLight);
          return panel;
     public void actionPerformed(ActionEvent event) {
          String command = event.getActionCommand();
          if (name.equals(command)) {
               component.setBackground (Color.BLACK);
               // Set redLight to black and greenLights background to gray
               redLight.setLight(false);
               redLight.setBackground(false);
               yellowLight.setBackground(false);
               greenLight.setBackground(false);
               repaint();
     static public class TlsLight extends JPanel {
          protected boolean isOn;
          protected boolean isNewProblem;
          protected int xPos;
          protected int yPos;
          protected int width = 80;
          protected int height = 80;
          protected Dimension preferredSize;
          protected Color theColor;
          protected Color background;
          private int insets = width/20;
          public TlsLight (Color aColor, boolean lightIsOn, boolean hasNewProblem) {
               theColor = aColor;
               isOn = lightIsOn;
               isNewProblem = hasNewProblem;
              preferredSize = new Dimension( width, height );
          public Dimension getPreferredSize() {
               return preferredSize;
          public void paint (Graphics graphics) {
               int diameter = width - 2 * insets;
               // Paint the background (square) based on Customer having a new problem or not
               if(isNewProblem) {
                    background = Color.GRAY;
               else {
                    background = Color.BLACK;
               graphics.setColor(background);
               graphics.fillRect(xPos + 10, yPos, width, height);
               // Set color light based on problemStatus
               if(isOn) {
                    graphics.setColor(theColor);
               } else {
                    graphics.setColor(background);
               graphics.fillOval(xPos + insets + 10, yPos + insets, diameter, diameter);
               // Set the background of the light
               graphics.setColor(Color.WHITE);         
               // Paint the background
               graphics.drawOval(xPos + insets + 10, yPos + insets, diameter, diameter);
          public void setLight (boolean setLight) {
               isOn = setLight;          
          public void setBackground (boolean setBackground) {
               isNewProblem = setBackground;
     public static void main (String [] args) {
          JFrame frame = new JFrame();
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          TrafficLight light = new TrafficLight("A Customer", "ERR", true);
          frame.add(light);
          frame.pack();
          frame.setVisible(true);
}The code contains both layouts, so it should not be a big problem to see what I mean. Hope someone can help me.
TIA,
Abel

Answer 1

Nest panels and layouts. Put the button in its own jpanel, set the panel's opaque to false so the underlying color comes through and then add the panel to the main panel:
        // Create the button containing the Customer name
        tlsButton = new JButton(name);
        tlsButton.setActionCommand(name);
        tlsButton.addActionListener(this);
        //using flowlayout is redundant here -- it's the default layout
        // but i'm doing this to illustrate what's happening.
        JPanel btnPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
        btnPanel.setOpaque(false);  // so underlying color isn't changed
        btnPanel.add(tlsButton);
        panel.add(btnPanel);