Tooltip for mousedragged

Question

I did a program in applet..I want to set tooltip for the drawing..i.e.,when the oval is dragged its new co-ordinates should be displayed by using the tooltip..How can i do this..
.import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import java.text.DateFormat;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import javax.swing.*;
import java.awt.*;
import java.awt.BorderLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.BorderFactory;
import javax.swing.border.Border;
public class mouseevent extends JApplet
      private static final int BALL_DIAMETER = 40; // Diameter of ball
    //--- instance variables
    /** Ball coords.  Changed by mouse listeners.  Used by paintComponent. */
    private int _ballX     = 450;   // x coord - set from drag
    private int _ballY     = 50;   // y coord - set from drag
    /** Position in ball of mouse press to make dragging look better. */
    private int _dragFromX = 0;    // pressed this far inside ball's
    private int _dragFromY = 0;    // bounding box.
    /** true means mouse was pressed in ball and still in panel.*/
    private boolean _canDrag  = false;
    JLabel label;
    String s= "aswedfrtyhgqwsadrftlopqasnhfgrchildnode1";   
    int width = s.length();   
    int border = 2;    int margin = 10;   
    int rectx = margin+border,recty =margin+border+63;   
    int rectwidth = 8, rectheight = 6;   
    int imgborder = 10;   
    int imgline1 = 300;  
    int labellocx = rectx+imgborder+13;  
    int labellocy = recty+imgborder-1;   
    int circlex = rectx+rectwidth;
    int circley = recty+rectheight;  
    int x =rectx+rectwidth+10;  
    int y = recty+rectheight+10;
    int x1 = x+17; 
    int y1 = y+20;  
    int titlebarx= 300;
    int titlebary = 40;  
    boolean title = true;
    String date[] = {"0","4","8","12","16","20","24"}; 
    String day[] = {"Mon","Tue","Wed","Thu","Fri","Sat"};
    int width1 = 180;
//    int f2= x+168;
    int n =180;
//    int dayx = 385;
    long From ;
    long To ;
    ArrayList dateList;
     int rect1x= 300;
    int rect1y = 100;
    int rect1width= 50;
    int rect1heigth = 50;
    boolean candrag = false;
    public void init()     
        Container cont = getContentPane();   
        cont.setLayout(new BorderLayout());
        // to see the scrollpane, the scrollpane has to be smaller        
        // then the component held within its viewport             
        setPreferredSize(new Dimension(300, 300));             
        JScrollPane scroll = new JScrollPane();              
        getContentPane().add(scroll, BorderLayout.CENTER);        
        scroll.getViewport().add(new Imagepanel());       
private class Imagepanel extends JPanel implements MouseListener,MouseMotionListener
        JScrollPane scroll = new JScrollPane();      
        Rectangle rect = new Rectangle(rectx,recty,rectwidth,rectheight);
        Rectangle rect1  = new Rectangle(rect1x,rect1y,rect1width,rect1heigth);
        Ellipse2D.Double circle = new Ellipse2D.Double(_ballX,_ballY,BALL_DIAMETER,BALL_DIAMETER);   
        Ellipse2D.Double circle1 = new Ellipse2D.Double(x+10,y+10,4,4);    
        boolean selected = false;  
        boolean selected1 = false;     
        int w ;     
    Imagepanel()       
        // setting the component to be largenr than the scrollpane           
        // just so we'll see scrollbars.
        setPreferredSize(new Dimension(32710,32710));      
        scroll = new JScrollPane();     
        add(scroll);                 
        addMouseListener(this);       
        addMouseMotionListener(this);
        setBorder(BorderFactory.createLineBorder(Color.BLACK, border));          
    protected void paintComponent(Graphics g)         
        int n = 168;
        int x = 300;
        int x1=300;
        int x2=x;
        int daydx=(width1/2);
        int dayx =(daydx+x);
        int f2= x+n;
        From = new java.util.GregorianCalendar(2007,01,01).getTime().getTime();
        To = new java.util.GregorianCalendar(2007,06,30).getTime().getTime();
        double Difference = To-From;
        long days = Math.round((Difference/(1000*60*60*24)));
        int noday = (int)days;
        Date fromDate = new java.util.GregorianCalendar(2007,01,01).getTime();
        Date toDate = new java.util.GregorianCalendar(2007,06,30).getTime();
        super.paintComponent(g);            
        Graphics2D g2 = (Graphics2D) g;             
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);       
        Font font = new Font("Ariel",Font.PLAIN,11); 
        Font font1 = new Font("Ariel",Font.PLAIN,9);
        g2.fillOval(_ballX, _ballY, BALL_DIAMETER-20, BALL_DIAMETER-20);
        g2.setBackground(Color.GRAY);
        //drawing the tilte bar     
        g2.setBackground(Color.WHITE);  
        g2.drawLine(imgline1,0,imgline1,getHeight()); 
        g2.setPaint(new Color(0,128,192));
        g2.fillRect(imgborder,imgborder,290,45);
        //g2.drawLine(margin,margin,titlebarx,titlebary);              
        //drawing the root node and labeling      
        g2.draw(rect);
        g2.setPaint(Color.WHITE);
        g2.drawLine(margin,margin,titlebarx,titlebary); 
        g2.drawString("RESOURCE",40,40);       
        g2.drawString("TIME",200,25);
        g2.setPaint(Color.green);
        g2.drawString("sadasd",344,22);
        g2.draw(circle);
        rect.setLocation(rectx,recty);      
        rect.setSize(rectwidth,rectheight);
        g2.setPaint(Color.BLACK);
        g2.drawString(" aswedfrtyhgqwsadrftlopqasnhfgrchildnode1",rectx+rectwidth+05,recty+rectheight);               
        for (int i = 0;i<noday;i++)
        Calendar  c = Calendar.getInstance(); // current date
            c.add(Calendar.DATE, i); // add one day
            SimpleDateFormat sdf = new  SimpleDateFormat("MM/dd/yy"); // use the pattern: day_of_month
            String str = sdf.format(c.getTime()); // fromat the date to string
            System.out.println(str); // print it at the console
            for (int j=0;j<6;j++)
                g2.setFont(font1);
                g2.drawLine(x1,40,x1,35);
                g2.drawString(date[j],x1,35);
//              g2.drawString(day[j],dayx,20);
                g2.drawString("24",f2,35);
                f2+=width1;
                x1+=30;
//              dayx=+170;
            g2.drawRect(x,10,width1,30);
            x+=width1;
            g2.drawString(str,dayx,20);
            dayx+=180;
        for(int k=0;k<n;k++)
            for(int l=0;l<6;l++)
            Calendar c = Calendar.getInstance(); // current datem
            c.add(Calendar.DAY_OF_WEEK, k); // add one day
            SimpleDateFormat sdf = new SimpleDateFormat("EEE"); // use the pattern: day_of_month
            String str = sdf.format(c.getTime()); // fromat the date to string
            System.out.println(str); // print it at the console
            g2.drawString(str,dayx,5);
//          g2.drawString(day[l],dayx,20);
            dayx+=180;
        //dividing the drawing panel      
        //drawing for the click event       
        if(selected)       
            Color color = Color.orange; 
            g2.fill(circle);
            g2.draw(circle);          
            //              g2.drawRoundRect(x+30,y+15,200,12,5,5);        
            g2.drawString("aswedfrtyhgqwsadrftlopqasnhfgrchildnode1",x+15,y+5);     
            g2.drawRect(300,y,100,15);      
        if(selected1)      
            g2.setFont(new Font("Arial",Font.PLAIN,12)); 
            g2.fill(circle1);
            g2.draw(circle1);           
            g2.drawString(" aswedfrtyhgqwsadrftlopqmasnhfgrchildnode1",x1+15,y1+5);  
    public void update(Graphics g)    
        paint(g);   
    public void mouseClicked(MouseEvent e)          
        //imagePaneMouseClicked(e);              
    private void imagePaneMouseClicked(MouseEvent e)        
        Point p = e.getPoint();         
        if (rect.contains(p))                  
            if (!selected)              
                selected = true;        
                repaint();               
        if(circle.contains(p))     
            if(!selected1)           
                selected1 = true;    
                repaint();           
        if(rect.contains(p)) 
            if(e.getClickCount() == 2)    
                selected = false;  
                repaint();      
    public void mousePressed(MouseEvent e)        
         int x = e.getX();   // Save the x coord of the click
        int y = e.getY();   // Save the y coord of the click
        if (x >= _ballX && x <= (_ballX + BALL_DIAMETER)
                && y >= _ballY && y <= (_ballY + BALL_DIAMETER)) {
            _canDrag = true;
            _dragFromX = x - _ballX;  // how far from left
            _dragFromY = y - _ballY;  // how far from top
        } else {
            _canDrag = false;
    public void mouseReleased(MouseEvent e) {        }               
    public void mouseEntered(MouseEvent e) {        }          
    public void mouseExited(MouseEvent e) { 
        candrag = false;
        public void mouseDragged(MouseEvent e) {
          if (_canDrag)
          {   // True only if button was pressed inside ball.
            //--- Ball pos from mouse and original click displacement
            _ballX = e.getX() - _dragFromX;
            _ballY = e.getY() - _dragFromY;
            //--- Don't move the ball off the screen sides
            _ballX = Math.max(_ballX, 0);
            _ballX = Math.min(_ballX, getWidth() - BALL_DIAMETER);
            //--- Don't move the ball off top or bottom
            _ballY = Math.max(_ballY, 0);
            _ballY = Math.min(_ballY, getHeight() - BALL_DIAMETER);
            this.repaint(); // Repaint because position changed.
            this.add(label);
            label.setText(""+_ballX+_ballY);
            label.setLocation(_ballX,_ballY);
        public void mouseMoved(MouseEvent e) {
}

Answer 1

The label is not getting displayed...the program throws some exception...
Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at java.awt.Container.addImpl(Container.java:1015)
at java.awt.Container.add(Container.java:351)
at javaapplication5.mouseevent$Imagepanel.mouseDragged(mouseevent.java:346)
at java.awt.Component.processMouseMotionEvent(Component.java:5536)
at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:3144)
at java.awt.Component.processEvent(Component.java:5257)
at java.awt.Container.processEvent(Container.java:1966)
at java.awt.Component.dispatchEventImpl(Component.java:3955)
at java.awt.Container.dispatchEventImpl(Container.java:2024)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3909)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822)
at java.awt.Container.dispatchEventImpl(Container.java:2010)
at java.awt.Component.dispatchEvent(Component.java:3803)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)