how to save the image?

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JTextField;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;


public class UserInterface 
{
    public static void main(String[] args) 
        {
                JFrame projectFrame = new JFrame();
                projectFrame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
                JPanel projectPanel = new JPanel();
                JPanel btnPanel = new JPanel();
                JButton encode = new JButton("ENCODE");
                JButton decode = new JButton("DECODE");
                
                encode.addActionListener(new ButtonListener());
                decode.addActionListener(new ButtonListener());
    
                projectFrame.setSize(600,500);
                projectFrame.setTitle("ONLINE SIGNATURE STEGANOGRAPHY");  
                projectFrame.setResizable(true);
                projectPanel.setLayout(new FlowLayout());
                
                JLabel stego = new JLabel("ONLINE SIGNATURE STEGANOGRAPHY SYSTEM");
                stego.setFont(new Font("Tahoma", Font.BOLD, 20));
                 
                projectFrame.add(projectPanel);
                projectFrame.add(btnPanel, BorderLayout.PAGE_END);
                projectPanel.add(stego);
                btnPanel.add(encode);
                btnPanel.add(decode);
                projectFrame.setVisible(true);
        }
        
        static class ButtonListener implements ActionListener   
 {         
  public void actionPerformed(ActionEvent ae) 
  {
   if(ae.getActionCommand().equals("ENCODE"))
   {
    new encodePane();
   }
   if(ae.getActionCommand().equals("DECODE"))
   {
    new decodePane();
   }
     
  }
 }
}
        

        class encodePane
        {

           public encodePane() 
            {
  final JFrame encodeFrame = new JFrame();
                Container content = encodeFrame.getContentPane();
                content.setLayout(new BorderLayout());
                JPanel encodePanel = new JPanel();
                JPanel buttonPanel = new JPanel();
                
                final PadDraw drawPad = new PadDraw();
                content.add(drawPad, BorderLayout.CENTER);
                
                JButton cancelBtn = new JButton("CANCEL");
                cancelBtn.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                encodeFrame.dispose();
                }
                });
  
                JButton proceedBtn = new JButton("PROCEED");
                proceedBtn.addActionListener(new ActionListener() { 
                public void actionPerformed(ActionEvent e){
                     new encode1Pane();
                     encodeFrame.dispose();
                     }   
                });  
                
                JButton clearButton = new JButton("CLEAR");
                //creates the clear button and sets the text as "Clear"
                clearButton.addActionListener(new ActionListener(){
                        public void actionPerformed(ActionEvent e){
                                drawPad.clear();
                        }
                });
                
                JLabel Sign = new JLabel("Sign here:", SwingConstants.CENTER);
                Sign.setVerticalAlignment(SwingConstants.TOP);
                                                              
               // proceedBtn.addActionListener(new Button1Listener());
                                
                encodeFrame.setTitle("ENCODE SECTION");
                encodeFrame.setLocationRelativeTo(null);   
                encodeFrame.setSize(600,500); 
                encodeFrame.setResizable(true);
                encodePanel.setLayout(new FlowLayout());
                
                encodePanel.add(Sign);
                                                 
                encodeFrame.add(encodePanel, BorderLayout.NORTH);
                encodeFrame.add(buttonPanel, BorderLayout.SOUTH);
                                                
                buttonPanel.setLayout(new BoxLayout(buttonPanel, BoxLayout.LINE_AXIS));
                buttonPanel.setBorder(BorderFactory.createEmptyBorder(0, 10, 10, 10));
                buttonPanel.add(Box.createHorizontalGlue());
                buttonPanel.add(clearButton);
                buttonPanel.add(Box.createRigidArea(new Dimension(10, 0)));
                buttonPanel.add(cancelBtn);
                buttonPanel.add(Box.createRigidArea(new Dimension(10, 0)));
                buttonPanel.add(proceedBtn);
                
                Sign.setFont(new Font("Serif", Font.ITALIC, 14));
                encodeFrame.setVisible(true);
 }
           
         
        /*static class Button1Listener implements ActionListener 
  {   
   public void actionPerformed(ActionEvent ae)  
   {
    if(ae.getActionCommand().equals("PROCEED"))
    {
                                    new encode1Pane();
                                }
                                                               
                        }
  }*/
       }

       class PadDraw extends JComponent{

            Image image;
            Graphics2D graphics2D;
            int currentX, currentY, oldX, oldY;

            public PadDraw(){
                setDoubleBuffered(false);
                addMouseListener(new MouseAdapter(){
                    public void mousePressed(MouseEvent e){
                        oldX = e.getX();
                        oldY = e.getY();
                    }
                });
            addMouseMotionListener(new MouseMotionAdapter(){
                public void mouseDragged(MouseEvent e){
                    currentX = e.getX();
                    currentY = e.getY();
                    if(graphics2D!=null)
                        graphics2D.drawLine(oldX, oldY, currentX, currentY);
                    repaint();
                    oldX = currentX;
                    oldY = currentY; 
                }
            });
            }
       public void paintComponent(Graphics g){
           if(image==null){
               image = createImage(getSize().width, getSize().height);
               graphics2D = (Graphics2D)image.getGraphics();
               graphics2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
               clear();
               
               }
           g.drawImage(image,0,0,null);
       }
       
       public void clear(){
           graphics2D.setPaint(Color.white);
           graphics2D.fillRect(0,0,getSize().width, getSize().height);
           graphics2D.setPaint(Color.black);
           repaint();
       }

}

       class encode1Pane
       {
           public encode1Pane()
           {
              final JFrame encode1Frame = new JFrame();
              JPanel Enc = new JPanel();
              JPanel enc = new JPanel();
              JPanel Btn = new JPanel();
              JButton prcd = new JButton ("ENCODE");
              JLabel sec = new JLabel ("Your message");
              final JTextField secText = new JTextField ("");
              secText.setPreferredSize(new Dimension (500, 100));
              JLabel name = new JLabel ("Set the file name");
              final JTextField name2 = new JTextField ();
              name2.setPreferredSize(new Dimension (200, 20));
              JButton cncl = new JButton ("CANCEL");
              cncl.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent e) {
                new encodePane();
                encode1Frame.dispose();
                }
                });
              
                            
              encode1Frame.setTitle("ENCODE SECTION");
              encode1Frame.setLocationRelativeTo(null);   
              encode1Frame.setSize(600,500);
              encode1Frame.setResizable(true);
                            
              Enc.add(sec);
              Enc.add(secText);
              secText.setBounds(30, 50, 200, 25);
              enc.add(name);
              enc.add(name2);
              name2.setBounds(30, 50, 200, 25);
              encode1Frame.add(Btn, BorderLayout.SOUTH);
              encode1Frame.add(Enc, BorderLayout.NORTH);
              encode1Frame.add(enc, BorderLayout.CENTER);
              encode1Frame.setVisible(true);   
                            
              Btn.setLayout(new BoxLayout(Btn, BoxLayout.LINE_AXIS));
              Btn.setBorder(BorderFactory.createEmptyBorder(0, 10, 10, 10));
              Btn.add(Box.createHorizontalGlue());
              Btn.add(cncl);
              Btn.add(Box.createRigidArea(new Dimension(10, 0)));
              Btn.add(prcd);
                
              
              sec.setFont(new Font("Serif", Font.ITALIC, 14));
              name.setFont(new Font("Serif", Font.ITALIC, 14));
              //cncl.addActionListener(new Button2Listener());
              prcd.addActionListener(new Button2Listener());
               
       }
           
           static class Button2Listener implements ActionListener 
  {   
   public void actionPerformed(ActionEvent ae)  
   {
    if(ae.getActionCommand().equals("Proceed"))
    {
      //new encodeOutput();
    }    
   }
                 }
       }

            
        class decodePane 
            {
               public decodePane() 
                {
                    JFrame decodeFrame = new JFrame();
                    decodeFrame.add(new UploadImage());
                           
                }}