Runtime help please

Question

Greetings,
First off I will admit that this a part of a project for school. I am not asking for anyone to "give me code" or to "do it for me". I am having a problem tracing a runtime error with the below code. The error only occurs when you choose a selection from the jmenu (null pointer execption on line xyz). the jmenu is supposed to update the display in the JComboBox via the setSelectedItem() and the null pointer points towards the line for the setSelectedItem(). Any assistance in pointing me towards the source of the error is appreciated.
source code follows:
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
class Polygon extends JFrame implements ActionListener
{   // start Polygon Class
     /* Variable Declarations */
     Color color = Color.red;
     JComboBox comboBox;
     boolean moving;
     boolean overload;
     /* End Variable Declarations */
     Polygon()
     { //start Polygon contructor
          addWindowListener(new WindowAdapter()
                    public void windowClosing(WindowEvent e)
                              System.exit(0);
               }); // ends anon class for window closing (ends program)
     /* Creation of the MenuBar */
     JMenuBar menu = new JMenuBar();
     JMenu menuColor = new JMenu("Color");
     JMenuItem makeRed = new JMenuItem("Red");
          menuColor.add(makeRed);
          makeRed.addActionListener(this);
     JMenuItem makeBlue = new JMenuItem("Blue");
          menuColor.add(makeBlue);
          makeBlue.addActionListener(this);
     JMenuItem makeGreen = new JMenuItem("Green");
          menuColor.add(makeGreen);
          makeGreen.addActionListener(this);
     JMenuItem makeYellow = new JMenuItem("Yellow");
          menuColor.add(makeYellow);
          makeYellow.addActionListener(this);
     menu.add(menuColor);
     setJMenuBar(menu);
     /* End Creation of the MenuBar */
     /* Creation of the Combo box*/
     Object [] items = {"Red", "Blue", "Green", "Yellow"};
     JComboBox comboBox = new JComboBox(items);
     getContentPane().add(comboBox, BorderLayout.SOUTH);
     comboBox.addActionListener(new ActionListener()
               { //start anon class
                    public void actionPerformed(ActionEvent e)
                         { //start action Performed
                              JComboBox comboBox = (JComboBox)e.getSource();
                              String comboString = (String)comboBox.getSelectedItem();
                                   if(comboString.equals("Red"))
                              color = Color.red;
                                   else if(comboString.equals("Green"))
                                        color = Color.green;
                                   else if(comboString.equals("Blue"))
                                        color = Color.blue;
                                   else if(comboString.equals("Yellow"))
                                        color = Color.yellow;
                         } //end actionPerformed
                    } //end anon class
               ); //end function call for anon class
     /* End Creation of the Combobox */
     }// end Polygon contructor
     public void actionPerformed(ActionEvent e)
     {  // begins Actions
          JMenuItem menu = (JMenuItem)e.getSource();
          String menuString = menu.getText();
     if(menuString.equals("Yellow"))
     color = Color.yellow;
     comboBox.setSelectedItem("Yellow");
     else if(menuString.equals("Red"))
     color = Color.red;
     comboBox.setSelectedItem("Red");
     else if(menuString.equals("Blue"))
     color = Color.blue;
     comboBox.setSelectedItem("Blue");
     else if(menuString.equals("Green"))
     color = Color.green;
     comboBox.setSelectedItem("Green");
     } //ends Actions
public static void main (String []args)
     JFrame frame = new Polygon();
     frame.setTitle("Project 3");
     frame.setSize(300, 300);
     frame.setVisible(true);
} //end main
}//end Ploygon Class

Answer 1

hi
I checked ur code.
the problem is that u have initialized objects more than one time un necesssarly.
my friend for selecting an item from a combo box there are some methods iside java plz refer to them.
do not use String .equal() ...
i am sue that u will get ue souirce code copiled if u remove those problem,s.