Question

I have this code which applies a counter to each item on the list. When the item reaches a certain number it is moved from jList3 to jList 1.

public Map<Object, Integer> buttonMap = new HashMap<Object, Integer>();
    private void jButton5ActionPerformed(java.awt.event.ActionEvent evt) {  

    Integer counter = null;
    int[] selection = jList3.getSelectedIndices();
     for (int i = 0; i < selection.length; i++){
        Object selString = jList3.getModel().getElementAt(selection[i]);
       counter = buttonMap.get(selString);      
        if(counter == null ) {           
            buttonMap.put(selString, new Integer(1));     
        }                                                                                                      
        else {
        buttonMap.put(selString, new Integer(counter.intValue() + 1)); 
        }           
        System.out.println(selString + " has been clicked " + buttonMap.get(selString) + " times.");                                      

       try{
        if (counter == 4){                          
           listModel2.removeElement(selString);
            listModel.addElement(selString);                             
        }
       }
        catch (NullPointerException npe1) {
        npe1.getMessage();
              }                                                                  
        }                                                   
  } 

The behavior comes in the if counter == 4 section.

It works fine but here is the weird part that I need help understanding

If I am counting up two items at the same time and they both reach the number that moves them on the same button click.

-It moves 1 of the items

-It does not count up on the other

-Instead it adds +1 to the counter of a non highlighted item

Example:

I am counting on list item 1 and 2, they both reach the max number, 1 gets moved 2 stays put(no increase in count) and item 3 gets +1 to counter

Answer 1

When you remove an element from jList3, the elements that follow are shifted.
I would sort the selection array and scan it in reverse order.

...
int[] selection = jList3.getSelectedIndices();
Arrays.sort(selection);
for (int i = selection.length; --i >= 0; ){
...

UPDATE: the sorting is not required, because the array returned by getSelectedIndices() already is