How can I limit the number of maximum selections for 1 selecting option of 20 JCombobox? javafor ex

Question

I have 9 (+ default) selectable options (all the same for the 20) for my JComboBoxes.
The 20 are part of 2 JComboBox array. (10-10 for each). I want to limit them like this:
If there is 4 selected from (for example) option 4 and the user selects a 5th
one of it, one of them jumps back to default to keep the limit of 4.

How Can I do it ?
for ex:

for (int i = 0; i < roles1.length; i++) {
            roles1[i] = new JComboBox();
            roles1[i].setModel(new DefaultComboBoxModel(new String[] { "Not Selected", "PartnerInCrime", "Driver",
                    "Gunman", "Coordinator", "Hacker", "Distraction", "GadgetGuy", "Bruglar", "ConMan" }));
            roles1[i].setBounds(boxPlace, 200, 100, 20);
            boxPlace += 105;
            getFrame().getContentPane().add(roles1[i]);

        }

Answer 1

Here is a suggestion which is supposed to lead you in the right direction.

First of all, you have to add an ActionListener to each ComboBox, that calls a method which compares all selections with your current one.

roles1[i].addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {

       // get the current selection
       JComboBox currentBox = (JComboBox)e.getSource();
       String currentSelection = (String)currentBox.getSelectedItem();

       // call the method and hand in your current selection
       checkForSelectionExceeding(currentSelection);            

    }
});

In your scanning method you should memorize the amount of matches while scanning. If your limit is exceeded, reset the current box to default and stop scanning. Something like this:

private void checkForSelectionExceeding(String currentSelection){
   int matches = 0;

   for(int i=0; i<roles1.length; i++) {
      if(roles1[i].getSelectedItem().equals(currentSelection)) {
         matches++;
      }

      if(matches > 4) {
         roles1[i].setSelectedItem("Not Selected");
         break;
      }
   }
}

You only have to refactor this solution a little in order to scan both arrays sequentially.

Hope this helps.