Applying a Counter to Item in List

I have a list that is poulated via a local text file. I have the following code that simple prints the selected item/items when the button is click.

private void jButton5ActionPerformed(java.awt.event.ActionEvent evt) {
    int[] selection = jList3.getSelectedIndices();
            //  selection.toString();
            for (int i = 0; i < selection.length; i++){
                Object selString = jList3.getModel(开发者_C百科).getElementAt(selection[i]);

                System.out.println(selString);

            }
    }

Instead of printing the item I would like each button click on each object to be recorded somehow. I have no idea what kind of component, method etc to implement. Any guidance is appreciated.

My end result will be something similar to this.

System.out.println(SelString has been clicked X amount of times);

Use a hash map with your objects (selString) as keys, and a counter as value. Something like:

private 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(0));
        }

        buttonMap.put(selString, new Integer(counter.intValue() + 1));
        System.out.println(selString + " has been clicked " + buttonMap.get(selString) + " times.");
    }
}

You can use PropertyChangeSupport to notify each time jList items are clicked, besides you should create a listener to receive events notification (through propertyChangeSupport.addPropertyChangeListener).

Once there, you can get the event properties such as the property name and property's new value which will be selected item on jList3 in this case, for counting how many times some item was clicked, you could use a HashMap, setting the key as the item index of jList and the associated value how many time the item has been clicked:

PropertyChangeSupport propertyChangeSupport = new PropertyChangeSupport(this);
HashMap<Integer, Integer> clickCounter = new HashMap<Integer, Integer>();

    public NewJFrame() {
        initComponents();
        propertyChangeSupport.addPropertyChangeListener(new PropertyChangeListener() {

            public void propertyChange(PropertyChangeEvent evt) {
                if (evt.getPropertyName().equals("selectedIndex")) {
                    System.out.println("Selected index: " + evt.getNewValue());
                    System.out.println("Selected text: " + jList3.getModel().getElementAt(evt.getNewValue()));
                    if (clickCounter.containsKey((Integer) evt.getNewValue())) {
                        clickCounter.put((Integer) evt.getNewValue(), clickCounter.get((Integer) evt.getNewValue()) + 1);
                    } else {
                        clickCounter.put((Integer) evt.getNewValue(), 1);
                    }
                }
            }
        });
    }

    private void jList1MouseClicked(java.awt.event.MouseEvent evt) {
        // TODO add your handling code here:
        propertyChangeSupport.firePropertyChange("selectedIndex", -1, jList3.getSelectedIndex());
    }

At any time you can retrive how many times certian item was clicked accessing clickCounter

I would suggest using an inner class which holds whatever object you are currently putting into the JList and adding a counter member variable as well as overriding the toString().

class MyListItem 
{
   int selectionCount;
   Object listItem; //may consider generics here, but left them out cause they can be tricky
   public MyListItem(Object item) 
   {
      selectionCount=0;
      listItem=item;
   }
   public void incrementSelectionCount()
   {
      selectionCount++;
   }
   public String toString()
   {
      return listItem.toString() + " has been clicked " + selectionCount + " times."); 
   }
}

Then in your action listener

private void jButton5ActionPerformed(java.awt.event.ActionEvent evt) 
{                   
    int[] selection = jList3.getSelectedIndices();                           

    for (int selectedIndex : selection)
    {
       Object selString = jList3.getModel().getElementAt(selectedIndex);
       if(selString instanceOf MyListItem)
       {
           MyListItem selItem = (MyListItem) selString;
           selItem.incrementSelectionCount();
           System.out.println(selString);  
       }                                        
    }                   
} 

This should save time on look ups, boxing, etc. Also, this helps keep things sane as the project grows since MyListItem can be grown to deal with all types of actions you may want in the future in case you want different things to happen for things other than button presses. The basic idea here is that the MyListItem should keep track of everything you are interested in tracking so you don't need multiple lists and even worse, to remember to add an item to both a JList and a HashMap or any other data structure. This way it's either on every data structure it needs to be or not at all.