import java . awt .*;
 import java . awt . event .*;
 import javax . swing .*;


public class DragBallPanel extends JPanel implements
MouseListener, MouseMotionListener{

	private static final int BALL_DIAMETER = 40;
	private int _ballX = 50;
	private int _ballY = 50;
	private int _dragFromX = 0;
	private int _dragFromY = 0;
	private boolean _canDrag = false ;


	public DragBallPanel () {
		setPreferredSize ( new Dimension (300 , 300) ) ;
	    setBackground ( Color . blue ) ;
		setForeground ( Color . yellow ) ;

		this . addMouseListener ( this ) ;
	    this . addMouseMotionListener ( this ) ;
	}
	public void paintComponent ( Graphics g ) {
		super . paintComponent ( g ) ;
	 g . fillOval ( _ballX , _ballY , BALL_DIAMETER , BALL_DIAMETER );
	}

	public void mousePressed ( MouseEvent e ) {
		 int x = e . getX () ;
		 int y = e . getY () ;

		 if ( x >= _ballX && x <= ( _ballX + BALL_DIAMETER )
		 && y >= _ballY && y <= ( _ballY + BALL_DIAMETER ) )
		{
		 _canDrag = true ;
		 _dragFromX = x - _ballX ;
		 _dragFromY = y - _ballY ;
		 } else {
		 _canDrag = false ;
		 }
		 }
	public void mouseDragged ( MouseEvent e ) {
		 if ( _canDrag ) {

		 _ballX = e . getX () - _dragFromX ;
		 _ballY = e . getY () - _dragFromY ;


		 _ballX = Math . max ( _ballX , 0) ;
		 _ballX = Math . min ( _ballX , getWidth () - BALL_DIAMETER
		) ;
		 _ballY = Math . max ( _ballY , 0) ;
		  _ballY = Math . min ( _ballY , getHeight () -
		 BALL_DIAMETER ) ;
		 this . repaint () ;}
		 }
		 public void mouseExited ( MouseEvent e ) {
			_canDrag = false ;
		 }
		 public void mouseMoved ( MouseEvent e ) {}

		  public void mouseEntered ( MouseEvent e ) {}

		  public void mouseClicked ( MouseEvent e ) {}

		  public void mouseReleased ( MouseEvent e ) {}





}

import java .awt .*;
import java . awt . event .*;
import javax . swing .*;
import javax . swing . event .*;

public class DragDemo {
	public static void main (String[] args) {
		JFrame window=new JFrame();
		window . setTitle (" Drag Demo ") ;
		 window . setDefaultCloseOperation ( JFrame . EXIT_ON_CLOSE ) ;
		 window . setContentPane ( new DragBallPanel () ) ;
		 window . pack () ;
		 window . show () ;
	}

}