Componet changing by mousemotionlistener

Question

I am trying to make two JLabels text change to show the x and y coords of a JPanel. The program works in the System.out line, but shows errors when trying to change the JLabels. Can this be done? Below is my code:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class mousetest extends JFrame implements MouseMotionListener {
     int x =0;
     int y=0;
     public JLabel labelx;
     public JLabel labely;
     public static void main(String args[]) {
          new mousetest();
     mousetest() {
          super("Mouse Position Reader");
          setDefaultCloseOperation(EXIT_ON_CLOSE);
          Container content = getContentPane();
          JPanel panel = new JPanel();
          panel.addMouseMotionListener(this);
          content.add(panel);
          JLabel labelx = new JLabel(" x = " + x);
          panel.add(labelx);
          JLabel labely = new JLabel("y = " + y);
          panel.add(labely);
          pack();
          setVisible(true);
     } //close mousetest()
     public void mouseMoved(MouseEvent event) {
          x=event.getX();
          y=event.getY();
          //System.out.println("X = " + x + " Y = " + y);
          labelx.setText("A");
          labely.setText("B");
     public void mouseDragged(MouseEvent evt) {
          //this method necessary to implement MouseMotionListener
          //needs no body to work
}//close class

Answer 1

JLabel labelx = new JLabel(" x = " + x);
panel.add(labelx);
JLabel labely = new JLabel("y = " + y);
panel.add(labely);Your problem is right there in the constructor. When you put the JLabel in front of labelx and labely, you are creating local variables. The global ones don't even get touched. Thus, in your listener, the labels are null. Change those lines to the following, and it works great.
labelx = new JLabel(" x = " + x);
panel.add(labelx);
labely = new JLabel("y = " + y);
panel.add(labely);