Calculating distance to center in java

Problem:

Create a java GUI application that creates the distance from a
point specified by a user to the center.

Output:

Solution:

//*****************DistanceToCenterFrame.java**************/
import javax.swing.JFrame;

public class DistanceToCenterFrame {

 
 public static void main(String[] args) {
  JFrame frame = new JFrame("Distance To Center");
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  
  frame.setContentPane(new DistanceToCenterPanel()); 
  frame.pack();
  frame.setVisible(true);
  
 }
}
//*****************DistanceToCenterPanel.java**************/
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.text.DecimalFormat;

import javax.swing.JPanel;

public class DistanceToCenterPanel extends JPanel{

 
 private final int WIDTH = 600, HEIGHT = 600;
 private int centerX, centerY;
 private double distance;
 private DecimalFormat fmt;
 private Point current;
 
 public DistanceToCenterPanel() {
  centerX = WIDTH/2; 
  centerY = HEIGHT/2;
  distance = 0; current = null;
  fmt = new DecimalFormat("0.##");
  
  addMouseListener(new OffCenterListener());
  
  setPreferredSize(new Dimension(WIDTH, HEIGHT));
  setBackground(Color.YELLOW);
 }
 @Override
 protected void paintComponent(Graphics g) {
  super.paintComponent(g);
  g.setColor(Color.BLACK);
  g.fillOval(centerX-3, centerY-3, 6, 6);
  
  if(current != null) {
   g.drawLine(current.x, current.y, centerX, centerY);
   g.drawString("Distance: " + fmt.format(distance), 5, 15);
  }
 } 
 
 private class OffCenterListener extends MouseAdapter {
  @Override
  public void mouseClicked(MouseEvent e) {
   current = e.getPoint();
   distance = Math.sqrt(Math.pow(current.x-centerX, 2) + Math.pow(current.y-centerY, 2));
   repaint();
   
  }
 }
 
}