Painting on JPanel problem

Question

i am new in java and im practicing on GUI...
i wrote this stupid GUI that draw shapes on a JPanel, when i minimize the window and maximize again shapes disapear, i have been told to use the paintComponent( ) instead of getGraphics( ) but i didnt know how since my program is made out of two class...
i will provide the code so please help a newbie
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.image.BufferedImage;
import java.awt.image.RasterFormatException;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
public class can extends JFrame {
    private JPanel pic = new JPanel();
    private JButton b1 = new JButton("Clear");
    private JButton b2 = new JButton("Quit");
    private JButton b3 = new JButton("Save");
    private JRadioButton r, c, s;
    private JPanel p = new JPanel();
    public can() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(800, 600);
        setTitle("Shape Drawer");
        setLayout(new BorderLayout());
        pic.setBackground(Color.white);
        pic.addMouseListener(new locationListener());
        this.add(pic, BorderLayout.CENTER);
        this.add(b1, BorderLayout.WEST);
        this.add(b2, BorderLayout.EAST);
        this.add(b3, BorderLayout.SOUTH);
        b1.addActionListener(new clearListener());
        b2.addActionListener(new quitListener());
        b3.addActionListener(new saveListener());
        r = new JRadioButton("rectangle");
        c = new JRadioButton("circle");
        s = new JRadioButton("square");
        ButtonGroup bg = new ButtonGroup();
        bg.add(r);
        bg.add(c);
        bg.add(s);
        r.setSelected(true);
        p.add(r);
        p.add(c);
        p.add(s);
        this.add(p, BorderLayout.NORTH);
    private class saveListener implements ActionListener {
         * Invoked when an action occurs.
        public void actionPerformed(ActionEvent e) {
            saveFile();
    private class clearListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            clear();
    private class quitListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            quit();
    private class locationListener implements MouseListener {
        public void mouseClicked(MouseEvent e) {
            shapes shape = new shapes();
            Graphics g = pic.getGraphics();
            if (r.isSelected()) {
                shape.rect(g, e.getX() - 30, e.getY() - 20);
            if (c.isSelected()) {
                shape.circles(g, e.getX() - 25, e.getY() - 25);
            if (s.isSelected()) {
                shape.squares(g, e.getX() - 25, e.getY() - 25);
         * Invoked when a mouse button has been pressed on a component.
        public void mousePressed(MouseEvent e) {
            //To change body of implemented methods use File | Settings | File Templates.
         * Invoked when a mouse button has been released on a component.
        public void mouseReleased(MouseEvent e) {
            //To change body of implemented methods use File | Settings | File Templates.
         * Invoked when the mouse enters a component.
        public void mouseEntered(MouseEvent e) {
            //To change body of implemented methods use File | Settings | File Templates.
         * Invoked when the mouse exits a component.
        public void mouseExited(MouseEvent e) {
            //To change body of implemented methods use File | Settings | File Templates.
    private void quit() {
        System.exit(0);
    private void clear() {
        pic.repaint();
    private void saveFile() {
        int count = 1;
        String fileName = "picture.jpeg";
        File file = new File(fileName);
        if (file.exists()) {
            System.out.println("hello motto");
            fileName = "picture"+count+".jpeg";
            System.out.println(fileName);
            count++;
            System.out.println(count);
        pic = (JPanel) getContentPane();
        int w = pic.getWidth();
        int h = pic.getHeight();
        BufferedImage image = (BufferedImage) pic.createImage(w, h);
        Graphics g = image.getGraphics();
        if (g.getClipBounds() != null) {
            g.setClip(0, 0, w, h);
        pic.paint(g);
        try {
            FileOutputStream out = new FileOutputStream(file);
            JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
            encoder.encode(image);
            out.flush();
            out.close();
        } catch (IOException ioe) {
        catch (RasterFormatException rfe) {
    public static void main(String[] args) {
        try {
            UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } catch (Exception e) {
            System.out.println("ERROR: " + e);
        can c = new can();
        c.setVisible(true);
}this was the first class and this is the second class that define the shapes
import java.awt.*;
public class shapes {
    public void squares(Graphics g, int x, int y) {
        g.setColor(Color.BLUE);
        g.fillRect(x, y, 50, 50);
    public void rect(Graphics g, int x, int y) {
        g.setColor(Color.RED);
        g.fillRect(x, y, 60, 40);
    public void circles(Graphics g, int x, int y) {
        g.setColor(Color.GREEN);
        g.fillOval(x, y, 50, 50);
}i dunno how and where to implement the paintComponent( ) in this situation , please help me... and im also having another problemin the saveFile( ) method in the can class, it doesnt increment the naming of the file if it already exists...
please help me...

Answer 1

Hey, there were a few design issues in your code so I hope you dont mind me re-coding a few section of it to bring out the usage of the paintComponent(Graphics g) method.
Also, the save was not working correctly because of the localization of the variables count and filename. I moved them and them global it to work. Also you had to re-create the file instance in order for it to be saved correctly with the new name.
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.io.*;
public class Can extends JFrame {
    private JPanel p = new JPanel();
    private JButton b1 = new JButton("Clear");
    private JButton b2 = new JButton("Quit");
    private JButton b3 = new JButton("Save");
    private JRadioButton r, c, s;
    private PicturePanel pic = new PicturePanel();  
    private boolean shdClear = false;
    public Can() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(800, 600);
        setTitle("Shape Drawer");
        setLayout(new BorderLayout());          
        JPanel buttonPanel = new JPanel();
            buttonPanel.add(b1);
            buttonPanel.add(b2);
            buttonPanel.add(b3);
        b1.addActionListener(new clearListener());
        b2.addActionListener(new quitListener());
        b3.addActionListener(new saveListener());      
        r = new JRadioButton("rectangle");       
        c = new JRadioButton("circle");
        s = new JRadioButton("square");       
        r.setSelected(true);
        p.add(r);
        p.add(c);
        p.add(s);
        ButtonGroup bg = new ButtonGroup();
            bg.add(r);
            bg.add(c);
            bg.add(s);
        getContentPane().add(pic, BorderLayout.CENTER);
        getContentPane().add(buttonPanel, BorderLayout.SOUTH );
        getContentPane().add(p, BorderLayout.NORTH);
    public class PicturePanel extends JPanel implements MouseListener {
        Shapes shape = new Shapes();
        MouseEvent e = null;
        BufferedImage backgroundImage = null;
        public PicturePanel() {
            super();
            setBackground(Color.white);
            addMouseListener(this);
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            if(e == null) {
                return;
            if(shdClear) {
                backgroundImage.getGraphics().dispose();
                backgroundImage = null;
            if(backgroundImage == null) {
                backgroundImage = new BufferedImage( getWidth(), getHeight(),
                    BufferedImage.TYPE_INT_RGB );
                Graphics g2 = backgroundImage.getGraphics();
                    g2.setColor( getBackground() );
                    g2.fillRect(0,0, getWidth(), getHeight());
                // added here for performance reasons
                // could have been added above in the if(shdClear) section 
                if(shdClear) {
                    shdClear = false;
                    return;
            Graphics g2 = backgroundImage.getGraphics();
            if (r.isSelected()) {
                shape.rect(g2, e.getX() - 30, e.getY() - 20);
            if (c.isSelected()) {
                shape.circles(g2, e.getX() - 25, e.getY() - 25);
            if (s.isSelected()) {
                shape.squares(g2, e.getX() - 25, e.getY() - 25);
            if(backgroundImage != null) {
                g.drawImage(backgroundImage, 0, 0, this);
        public void mouseClicked(MouseEvent e) {
            this.e = e;
            pic.repaint();
         * Invoked when a mouse button has been pressed on a component.
        public void mousePressed(MouseEvent e) {
            //To change body of implemented methods use File | Settings | File Templates.
         * Invoked when a mouse button has been released on a component.
        public void mouseReleased(MouseEvent e) {
            //To change body of implemented methods use File | Settings | File Templates.
         * Invoked when the mouse enters a component.
        public void mouseEntered(MouseEvent e) {
            //To change body of implemented methods use File | Settings | File Templates.
         * Invoked when the mouse exits a component.
        public void mouseExited(MouseEvent e) {
            //To change body of implemented methods use File | Settings | File Templates.
    private class saveListener implements ActionListener {
         * Invoked when an action occurs.
        public void actionPerformed(ActionEvent e) {
            saveFile();
    private class clearListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {           
            clear();
    private class quitListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            quit();
    private void quit() {
        System.exit(0);
    private void clear() {
        shdClear = true;
        pic.repaint();
    int count = 1; // moved so as not be recreated each time
    String fileName = "picture.jpeg";
    private void saveFile() {
        File file = new File(fileName);
        while (file.exists()) {
            System.out.println("hello motto");
            fileName = "picture" + count + ".jpeg";
            System.out.println(fileName);
            count++;
            System.out.println(count);
            file = new File(fileName); // recreate the file
        //pic = (JPanel) getContentPane();
        int w = pic.getWidth();
        int h = pic.getHeight();
        BufferedImage image = (BufferedImage) pic.createImage(w, h);
        Graphics g = image.getGraphics();
        if (g.getClipBounds() != null) {
            g.setClip(0, 0, w, h);
        pic.paint(g);
        try {
            FileOutputStream out = new FileOutputStream(file);
            JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
            encoder.encode(image);
            out.flush();
            out.close();
            JOptionPane.showMessageDialog(null, fileName + " Saved", "File Saved",
            JOptionPane.INFORMATION_MESSAGE);
        } catch (IOException ioe) {
        } catch (RasterFormatException rfe) {
    public static void main(String[] args) {
        try {
            UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } catch (Exception e) {
            System.out.println("ERROR: " + e);
        Can c = new Can();
        c.setVisible(true);
class Shapes {
    public void squares(Graphics g, int x, int y) {
        g.setColor(Color.BLUE);
        g.fillRect(x, y, 50, 50);
    public void rect(Graphics g, int x, int y) {
        g.setColor(Color.RED);
        g.fillRect(x, y, 60, 40);
    public void circles(Graphics g, int x, int y) {
        g.setColor(Color.GREEN);
        g.fillOval(x, y, 50, 50);
}ICE