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    <p>I assume you are drawing to the <code>JPanel</code> by using <code>getGraphics()</code> and rendering your out put to it.</p> <p>You have now seen why you shouldn't do this. When the component is repainted, anything previously painted to is wiped cleaned and you are expected to repaint the contents.</p> <p>Start by overriding <code>paintComponent</code> and updating all the lines within this method (don't forget to call <code>super.paintComponent</code></p> <p>See <a href="http://docs.oracle.com/javase/tutorial/uiswing/painting/" rel="nofollow noreferrer">Performing Custom Painting</a> and <a href="http://www.oracle.com/technetwork/java/painting-140037.html" rel="nofollow noreferrer">Painting in AWT and Swing</a> for more details</p> <p>For example..</p> <ul> <li><a href="https://stackoverflow.com/questions/12683533/drawing-a-rectangle-that-wont-disappear-in-next-paint/12683601#12683601">Drawing a rectangle that won&#39;t disappear in next paint</a></li> <li><a href="https://stackoverflow.com/questions/14764157/mouseevent-is-not-registering-a-release-when-i-release-the-mouse-button/14764264#14764264">MouseEvent is not registering a release when I release the mouse button</a></li> </ul> <p><strong>Updated with example</strong></p> <p>This is a modified version of the answer to <a href="https://stackoverflow.com/questions/14764157/mouseevent-is-not-registering-a-release-when-i-release-the-mouse-button/14764264#14764264">MouseEvent is not registering a release when I release the mouse button</a> which includes a scroll pane...</p> <p><img src="https://i.stack.imgur.com/SWjSJ.png" alt="enter image description here"></p> <pre><code>import java.awt.Dimension; import java.awt.EventQueue; import java.awt.Graphics; import java.awt.Point; import java.awt.event.MouseAdapter; import java.awt.event.MouseEvent; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.UIManager; public class MouseDraggedTest { public static void main(String[] args) { new MouseDraggedTest(); } public MouseDraggedTest() { EventQueue.invokeLater(new Runnable() { @Override public void run() { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (Exception ex) { } JFrame frame = new JFrame("Test"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.add(new JScrollPane(new TestPane())); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } }); } public class TestPane extends JPanel { private Map&lt;Point, List&lt;Point&gt;&gt; mapPoints; private Point currentPoint; public TestPane() { mapPoints = new HashMap&lt;&gt;(25); MouseAdapter mouseListener = new MouseAdapter() { @Override public void mousePressed(MouseEvent e) { currentPoint = e.getPoint(); mapPoints.put(currentPoint, new ArrayList&lt;Point&gt;(25)); } @Override public void mouseReleased(MouseEvent e) { List&lt;Point&gt; points = mapPoints.get(currentPoint); if (points.isEmpty()) { mapPoints.remove(currentPoint); } currentPoint = null; } @Override public void mouseDragged(MouseEvent me) { List&lt;Point&gt; points = mapPoints.get(currentPoint); points.add(me.getPoint()); repaint(); } }; addMouseListener(mouseListener); addMouseMotionListener(mouseListener); } @Override public Dimension getPreferredSize() { return new Dimension(200, 800); } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); for (Point startPoint : mapPoints.keySet()) { List&lt;Point&gt; points = mapPoints.get(startPoint); for (Point p : points) { if (startPoint != null) { g.drawLine(startPoint.x, startPoint.y, p.x, p.y); } startPoint = p; } } } } } </code></pre> <p><strong>Updated with a BufferedImage example</strong></p> <p>Because you need to supply more operations than just drawing, you may find it easier to use <code>BufferedImage</code> as your primary drawing surface and render this to your <code>DrawingPanel</code></p> <p><img src="https://i.stack.imgur.com/JL7vO.png" alt="enter image description here"></p> <pre><code>import java.awt.BasicStroke; import java.awt.BorderLayout; import java.awt.Color; import java.awt.Dimension; import java.awt.EventQueue; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.GridBagConstraints; import java.awt.GridBagLayout; import java.awt.Point; import java.awt.Shape; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.MouseAdapter; import java.awt.event.MouseEvent; import java.awt.geom.Ellipse2D; import java.awt.geom.Line2D; import java.awt.image.BufferedImage; import javax.swing.ButtonGroup; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JToggleButton; import javax.swing.UIManager; import javax.swing.UnsupportedLookAndFeelException; public class MyPicture { public static void main(String[] args) { new MyPicture(); } public MyPicture() { EventQueue.invokeLater(new Runnable() { @Override public void run() { try { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) { } JFrame frame = new JFrame("Testing"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setLayout(new BorderLayout()); frame.add(new TestPane()); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } }); } public enum DrawOperation { Draw, Erase } public class TestPane extends JPanel { private DrawOperation op; private JToggleButton pencil; private JToggleButton eraser; private DrawPane drawPane; public TestPane() { setLayout(new BorderLayout()); drawPane = new DrawPane(); MouseAdapter adapter = new MouseAdapter() { private Point startPoint; @Override public void mouseEntered(MouseEvent e) { drawPane.updateDrawCursor(e.getPoint(), op); } @Override public void mouseExited(MouseEvent e) { drawPane.removeDrawCursor(); } @Override public void mousePressed(MouseEvent e) { startPoint = e.getPoint(); } @Override public void mouseReleased(MouseEvent e) { startPoint = null; } @Override public void mouseDragged(MouseEvent e) { drawPane.applyOperation(startPoint, e.getPoint(), op); drawPane.updateDrawCursor(e.getPoint(), op); startPoint = e.getPoint(); } @Override public void mouseMoved(MouseEvent e) { drawPane.updateDrawCursor(e.getPoint(), op); } }; drawPane.addMouseListener(adapter); drawPane.addMouseMotionListener(adapter); JPanel operations = new JPanel(new GridBagLayout()); GridBagConstraints gbc = new GridBagConstraints(); gbc.gridwidth = GridBagConstraints.REMAINDER; pencil = new JToggleButton("Draw"); eraser = new JToggleButton("Erase"); ButtonGroup bgOps = new ButtonGroup(); bgOps.add(pencil); bgOps.add(eraser); operations.add(pencil, gbc); operations.add(eraser, gbc); pencil.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { op = DrawOperation.Draw; } }); eraser.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { op = DrawOperation.Erase; } }); add(operations, BorderLayout.WEST); add(new JScrollPane(drawPane)); } } public class DrawPane extends JPanel { private BufferedImage image; private Shape drawCursor; private Point cursorPoint; private int eraseSize = 20; public DrawPane() { image = new BufferedImage(400, 400, BufferedImage.TYPE_INT_RGB); Graphics2D g2d = image.createGraphics(); g2d.setBackground(Color.WHITE); g2d.fillRect(0, 0, 400, 400); g2d.dispose(); } @Override public Dimension getPreferredSize() { return new Dimension(400, 400); } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2d = (Graphics2D) g.create(); if (image != null) { g2d.drawImage(image, 0, 0, this); } if (drawCursor != null &amp;&amp; cursorPoint != null) { int x = (cursorPoint.x - (drawCursor.getBounds().width) / 2); int y = (cursorPoint.y - (drawCursor.getBounds().height) / 2); g2d.translate(x, y); g2d.draw(drawCursor); g2d.translate(-x, -y); } g2d.dispose(); } public void updateDrawCursor(Point point, DrawOperation op) { cursorPoint = point; if (op != null) { switch (op) { case Draw: drawCursor = new Ellipse2D.Float(0, 0, 4, 4); break; case Erase: drawCursor = new Ellipse2D.Float(0, 0, eraseSize, eraseSize); break; } } else { drawCursor = null; } repaint(); } protected void removeDrawCursor() { drawCursor = null; repaint(); } protected void applyOperation(Point fromPoint, Point toPoint, DrawOperation op) { if (image != null) { if (op != null) { Graphics2D g2d = image.createGraphics(); switch (op) { case Draw: g2d.setColor(Color.BLACK); g2d.draw(new Line2D.Float(fromPoint, toPoint)); break; case Erase: g2d.setColor(Color.WHITE); g2d.setStroke(new BasicStroke(eraseSize)); g2d.draw(new Line2D.Float(fromPoint, toPoint)); break; } g2d.dispose(); } } repaint(); } } } </code></pre>
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    1. POResize the panel without revalidation
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    1. COSir can we add this code in already created JPanel like drawPanel ? Because I'm facing problem in paintComponent() method when I write drawPanel.paintComponent(g); It says that paintComponent(Graphics) has protected access in JComponent.
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    2. COYou should never call paintComponent yourself. It will be called by the RepaintManager automatically. Have you read through the supplied links?
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    3. CONow I'm reading those links. Before that I was just try to implement it as soon as possible.
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