Dynamic JComboBox small bug...

Question

Hey,
I have made the following script to create a JComboBox containing car makes, which has an actionListener on it, so when a car make is selected the model can be set and a JComboBox for the model is created:
        String[] carManString = { "Audi", "BMW", "Ford", "Fiat", "Nissan", "Rover", "Volkswagen", "Vauxhall" };
        JComboBox carManList = new JComboBox(carManString);
        carManList.setSelectedIndex(0);
        carManList.setBounds( 125, 20, 120, 20 );
        policyPanel.add( carManList );
        // add actionListener to set specific model for make
        carManList.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {           
                JComboBox carManList = (JComboBox)e.getSource(); //find out car make
                final String carMake = (String)carManList.getSelectedItem();          
                Runnable updateAComponent = new Runnable() {
                public void run() {
                if( carMake == "Audi" )
                {   String[] carModelString = { "Audi_1", "Audi_2", "Audi_3", "Audi_4", "Audi_5" }; 
                JComboBox carModelList = new JComboBox(carModelString); //create combo box for model
                carModelList.setSelectedIndex(0);
                carModelList.setBounds( 305, 20, 120, 20 );
                policyPanel.remove( carModelList ); // remove previously selected models from panel
                policyPanel.add( carModelList ); // add new combobox of models
                else if ( carMake == "BMW" )
                {   String[] carModelString = { "BMW_1", "BMW_2", "BMW_3", "BMW_4", "BMW_5" }; 
                JComboBox carModelList = new JComboBox(carModelString);
                carModelList.setSelectedIndex(0);
                carModelList.setBounds( 305, 20, 120, 20 );
                policyPanel.remove( carModelList );
                policyPanel.add( carModelList );  
                else if ( carMake == "Ford" )
                {   String[] carModelString = { "Ford_1", "Ford_2", "Ford_3", "Ford_4", "Ford_5" }; 
                JComboBox carModelList = new JComboBox(carModelString);
                carModelList.setSelectedIndex(0);
                carModelList.setBounds( 305, 20, 120, 20 );
                policyPanel.remove( carModelList );
                policyPanel.add( carModelList );  
                else if ( carMake == "Fiat" )
                {   String[] carModelString = { "Fiat_1", "Fiat_2", "Fiat_3", "Fiat_4", "Fiat_5" }; 
                JComboBox carModelList = new JComboBox(carModelString);
                carModelList.setSelectedIndex(0);
                carModelList.setBounds( 305, 20, 120, 20 );
                policyPanel.remove( carModelList );
                policyPanel.add( carModelList );  
                else if ( carMake == "Nissan" )
                {   String[] carModelString = { "Nissan_1", "Nissan_2", "Nissan_3", "Nissan_4", "Nissan_5" }; 
                JComboBox carModelList = new JComboBox(carModelString);
                carModelList.setSelectedIndex(0);
                carModelList.setBounds( 305, 20, 120, 20 );
                policyPanel.remove( carModelList );
                policyPanel.add( carModelList );          
                else if ( carMake == "Rover" )
                {   String[] carModelString = { "Rover_1", "Rover_2", "Rover_3", "Rover_4", "Rover_5" }; 
                JComboBox carModelList = new JComboBox(carModelString);
                carModelList.setSelectedIndex(0);
                carModelList.setBounds( 305, 20, 120, 20 );
                policyPanel.remove( carModelList );
                policyPanel.add( carModelList );   
                else if ( carMake == "Volkswagen" )
                {   String[] carModelString = { "Volkswagen_1", "Volkswagen_2", "Volkswagen_3", "Volkswagen_4", "Volkswagen_5" }; 
                JComboBox carModelList = new JComboBox(carModelString);
                carModelList.setSelectedIndex(0);
                carModelList.setBounds( 305, 20, 120, 20 );
                policyPanel.remove( carModelList );
                policyPanel.add( carModelList );  
                else if ( carMake == "Vauxhall" )
                {   String[] carModelString = { "Vauxhall_1", "Vauxhall_2", "Vauxhall_3", "Vauxhall_4", "Vauxhall_5" }; 
                JComboBox carModelList = new JComboBox(carModelString);
                carModelList.setSelectedIndex(0);
                carModelList.setBounds( 305, 20, 120, 20 );
                policyPanel.remove( carModelList );
                policyPanel.add( carModelList );  
SwingUtilities.invokeLater(updateAComponent);
        });This seems to work fine apart from a few small problems.
The first is that the model comboBox only update after the make is chosen, then if you click somewhere on the JFrame it will update...should it not update immediatly when a selection is made?
The second problem is, if I click on the model combobox and select a model, the models change back to whatever the first make was selected...so if i choose Audi, then BMW and click the model combobox it will change back to the Audi models...
Any help greatly appretiated...
-Ross

Answer 1

removing/adding you need to include a validate, but looking at your code a bit more , this
might be all you need to do (you'll need additional code for any event of picking eg Audi_3)
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Testing extends JFrame
  String[] carManString = { "Audi", "BMW", "Ford", "Fiat", "Nissan", "Rover", "Volkswagen", "Vauxhall" };
  JComboBox carManList = new JComboBox(carManString);
  public Testing()
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setSize(200,100);
    setLocation(400,300);
    carManList.setSelectedIndex(0);
    carManList.addActionListener(new ActionListener(){
      public void actionPerformed(ActionEvent e){
        String[][] modelStrings =
          {{ "Audi_1", "Audi_2", "Audi_3", "Audi_4", "Audi_5" },
           { "BMW_1", "BMW_2", "BMW_3", "BMW_4", "BMW_5" },
           { "Ford_1", "Ford_2", "Ford_3", "Ford_4", "Ford_5" },
           { "Fiat_1", "Fiat_2", "Fiat_3", "Fiat_4", "Fiat_5" },
           { "Nissan_1", "Nissan_2", "Nissan_3", "Nissan_4", "Nissan_5" },
           { "Rover_1", "Rover_2", "Rover_3", "Rover_4", "Rover_5" },
           { "Volkswagen_1", "Volkswagen_2", "Volkswagen_3", "Volkswagen_4", "Volkswagen_5" },
           { "Vauxhall_1", "Vauxhall_2", "Vauxhall_3", "Vauxhall_4", "Vauxhall_5" }};
        DefaultComboBoxModel newModel = new DefaultComboBoxModel(modelStrings[carManList.getSelectedIndex()]);
        carManList.setModel(newModel);
        carManList.removeActionListener(this);}});
    JPanel jp = new JPanel();
    jp.add(carManList);
    getContentPane().add(jp);
  public static void main(String[] args){new Testing().setVisible(true);}
}