Using Action/Item Listener with JComboBox

Question

I've been trying to make a listener (I'm not really sure whether I should be using an ItemListener or ActionListener) respond to changes in a JComboBox by changing a JLabel image next to the box.

I tried defining the actionPerformed method in the constructor of the class under the addActionListener call on the combo box, as well as outside the constructor, and the actionPerformed never seems to execute. I've added a println to each one to test whether the method is actually working when I select an item in the box, but neither one appears to output anything, leading me to believe the actionPerformed method is not executing for some reason. A lot of different answers elsewhere have defined actionListeners and actionPerformed in multiple different places, such as a separate class or in an instance variable declaration.

public class MainBattle
{   
//instance variables

public MainBattle() throws FileNotFoundException,IOException
{
    //creation of ArrayLists used later

    for(JComboBox<String> j : party1)
    {
        j.addActionListener(new ActionListener()
        {
        public void actionPerformed(ActionEvent e)
        {
            System.out.println("Listener active");
            if(e.getSource() instanceof JComboBox)
            {
                JComboBox<String> cb = (JComboBox<String>)e.getSource();
                String content = (String)cb.getSelectedItem();
                if(party1.indexOf(cb) != -1)
                {
                    party1Image.get(party1.indexOf(cb)).setIcon(new ImageIcon(".\\res\\sprites_small\\"
                            + content.substring(0,content.indexOf(" ")) + ".png"));
                }
            }

            selectFrame.revalidate();
            selectFrame.repaint();
        }
        });
    }

    createUI();
}

public void createUI()
{
    //building GUI elements and displaying

    for(int i = 0; i < 6; i++)
    {
        party1.add(new JComboBox<String>());
        party2.add(new JComboBox<String>());
    }

    for(int i = 0; i < 6; i++)
    {
        party1Image.add(new JLabel(new ImageIcon(".\\res\\sprites_small\\0.png")));
        party2Image.add(new JLabel(new ImageIcon(".\\res\\sprites_small\\0.png")));
    }

    //building GUI elements and displaying
}

// Commented out to make sure existence of multiple methods is not problematic
/*
public void actionPerformed(ActionEvent e)
{
    System.out.println("Action");
}
*/

public static void main(String[] args) throws IOException
{
    new MainBattle();
}

}