Adding a listener to an integer value?

Question

Hello All
Is there a way of adding a listener to an integer value that produce an event (run a method with the object) when an integer value is changed? (Through a object.setValue(int) for example)
Thanks for any help,
Harold Clements

Answer 1

Can any of the kilo-posters (that's with two o's) say if it's considered
bad form to reuse a class that already exists - albeit for a slighty
different purpose? What I'm thinking is that the SpinnerNumberModel
is rather close to what's being looked for - the differences being that
it'll handle any Numbers and has a "next" functionality that we ignore.
Something like:import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SpinnerNumberModel;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
public class NumberEg extends JFrame {
     private SpinnerNumberModel intModel;
     private Random rand = new Random();
     private JLabel aLabel;
     public NumberEg() {
               // a thing that responds to changes - there could be
               // many of these
          aLabel = new JLabel("I respond to changes...");
          add(aLabel, BorderLayout.CENTER);
               // the thing which changes
          intModel = new SpinnerNumberModel(0, null, null, 0);
               // a change listener which glues the two previous
               // together - again there could be a number of these
          intModel.addChangeListener(new ChangeListener(){
               public void stateChanged(ChangeEvent evt) {
                    aLabel.setText(intModel.getValue().toString());
               // Meanwhile events like button clicks *cause* the
               // changes
          JButton but = new JButton("Click me!");
          but.addActionListener(new ActionListener(){
               public void actionPerformed(ActionEvent evt) {
                    intModel.setValue(rand.nextInt());
          add(but, BorderLayout.NORTH);
          but = new JButton("Reset");
          but.addActionListener(new ActionListener(){
               public void actionPerformed(ActionEvent evt) {
                    intModel.setValue(0);
          add(but, BorderLayout.SOUTH);
          setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          pack();
     public static void main(String args[]) {
          NumberEg test = new NumberEg();
          test.setVisible(true);
}