Problem - Refreshing JPanel with BufferedImage Object

//This is my getImg method of TestPanel
public BufferedImage getImg() {
		return img;
	} 
//This is what i am doing in mousereleased method
public void mouseReleased(MouseEvent e) {
		
		tp.setEndpt(e.getPoint());
		tp.undoredo.add(new  StoreBufferedImage(tp.getImg(),count++));
		tp.drawBox(false);		
		
	} 

                                              

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//Object stored in vector
public class StoreBufferedImage  {
	private BufferedImage bufferimage;
	private int current_index;
	public StoreBufferedImage(BufferedImage bufferimage, int current_index) {
		super();
		this.bufferimage = bufferimage;
		this.current_index = current_index;
	}
	public BufferedImage getBufferimage() {
		return bufferimage;
	}
	public void setBufferimage(BufferedImage bufferimage) {
		this.bufferimage = bufferimage;
	}
	public int getCurrent_index() {
		return current_index;
	}
	public void setCurrent_index(int current_index) {
		this.current_index = current_index;
	}
	
} 
//Mouse Listener
public class TestMouseListener extends MouseAdapter{ 
	TestPanel tp;
	int count=1;
	public TestMouseListener(TestPanel tp)
	{
		this.tp=tp;
	}
	@Override
	public void mousePressed(MouseEvent e) {
		
		super.mousePressed(e);
		
		tp.setStartpt(e.getPoint());
		
	} 
	@Override
	public void mouseReleased(MouseEvent e) {
		// TODO Auto-generated method stub
		tp.setEndpt(e.getPoint());
		BufferedImage timg=tp.getImg();
		tp.undoredo.add(new StoreBufferedImage(timg,count++));
		tp.drawBox(false);	
		
		
	} 
	
} 
public class TestMouseMotionListener extends MouseMotionAdapter {
      TestPanel tp;      
      
      public TestMouseMotionListener(TestPanel tp)
      {
    	  this.tp=tp;
      }
	@Override
	public void mouseDragged(MouseEvent e) {		
		super.mouseDragged(e);				
		tp.setEndpt(e.getPoint());		
		tp.drawBox(true);		
	}
      
} 

public class TestPanel extends JPanel implements Serializable { 
	
	private Point startpt;
	private Point endpt;
	private TestFrame tf;
	private BufferedImage img;
	
	
	
	
	public Vector<StoreBufferedImage> undoredo=new Vector<StoreBufferedImage>();
	
	public TestPanel(TestFrame tf,int w,int h)
	{
		this.tf=tf;    
		this.setSize(w, h);
        img=new BufferedImage(w,h,BufferedImage.TYPE_INT_RGB);
        setImg(img);     
        Graphics2D gd=img.createGraphics();
        gd.setPaint(Color.WHITE);
        gd.fillRect(0, 0, w, h);
        gd.dispose(); 
	} 
public void paintComponent(Graphics g) {
		super.paintComponent(g);
		g.drawImage(getImg(), 0, 0, (int)(getImg().getWidth()),(int)(getImg().getHeight()), this); 
	} 
 
	public BufferedImage getImg() {
		return img;
	} 
 
	public void setImg(BufferedImage img) {
		this.img = img;
		repaint();
	}
	
//method called on clicking undo button
	public void undoAction()
	{
		System.out.println("size=" + undoredo.size());
		StoreBufferedImage sbi=(StoreBufferedImage)undoredo.firstElement();		
		setImg(sbi.getBufferimage());		
		repaint();
		
	} 
public synchronized void drawBox(boolean type)
	{
		repaint();
		Graphics2D gd=(Graphics2D)getImg().getGraphics();
		gd.setColor(Color.BLACK);
		int w=(int)(getEndpt().getX()-getStartpt().getX());
		if(w<0)
		{
			w*=-1;
		}		
		int h=(int)(getEndpt().getY() - getStartpt().getY());
		if(h<0)
		{
			h*=-1;
		}
		
		
		gd.drawRect((int)getStartpt().getX(), (int)getStartpt().getY(), w, h);
		
		
		if(type)
		{
			
			gd.setColor(getBackground());		
			gd.fillRect((int)getStartpt().getX(), (int)getStartpt().getY(), w, h);
			
		}
		
		gd.dispose();
		repaint();
		
		
	} 
}
	
                                              

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