Question

I’ve implemented a ComboBox using NetBeans that has a list of values, I want to be able to perform an action whenever the selected index has changed. An example being when a user changes the current item from Item 1 to Item 2.

Answer 1

Here’s a usage example from The Java Tutorials:

public class ComboBoxDemo ... implements ActionListener {
    . . .
        petList.addActionListener(this) {
    . . .
    public void actionPerformed(ActionEvent e) {
        JComboBox cb = (JComboBox)e.getSource();
        String petName = (String)cb.getSelectedItem();
        updateLabel(petName);
    }
    . . .
}

Edit:

An ActionListener is

The listener interface for receiving
action events. The class that is
interested in processing an action
event implements this interface, and
the object created with that class is
registered with a component, using the
component’s addActionListener method.
When the action event occurs, that
object’s actionPerformed method is
invoked.

Edit 2:

Here’s another usage example to satisfy kleopatra, that is, one that is more exemplary of best practices:

JComboBox yourComboBox = new JComboBox();
yourComboBox.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        // do stuff
    }
});