public static void main(String[] args) {
    final javax.swing.JFrame frame = new javax.swing.JFrame();
    frame.setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
    frame.getContentPane().setLayout(new java.awt.GridBagLayout());
    java.awt.GridBagConstraints gridBagConstraints;
    final javax.swing.JButton jButtonDrawEllipse = new javax.swing.JButton();
    final javax.swing.JButton jButtonDrawRect = new javax.swing.JButton();
    final javax.swing.JPanel jDrawingPanel = new javax.swing.JPanel();

    jDrawingPanel.setBorder(javax.swing.BorderFactory.createEtchedBorder());

    javax.swing.GroupLayout jDrawingPanelLayout = new javax.swing.GroupLayout(jDrawingPanel);
    jDrawingPanel.setLayout(jDrawingPanelLayout);
    jDrawingPanelLayout.setHorizontalGroup(
        jDrawingPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 455, Short.MAX_VALUE)
    );
    jDrawingPanelLayout.setVerticalGroup(
        jDrawingPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 249, Short.MAX_VALUE)
    );

    gridBagConstraints = new java.awt.GridBagConstraints();
    gridBagConstraints.gridx = 0;
    gridBagConstraints.gridy = 1;
    gridBagConstraints.gridwidth = 2;
    gridBagConstraints.fill = java.awt.GridBagConstraints.BOTH;
    gridBagConstraints.weightx = 0.1;
    gridBagConstraints.weighty = 0.1;
    gridBagConstraints.insets = new java.awt.Insets(5, 5, 5, 5);
    frame.getContentPane().add(jDrawingPanel, gridBagConstraints);

    jButtonDrawRect.setText("Square");
    jButtonDrawRect.addActionListener(new java.awt.event.ActionListener() {
        @Override
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jDrawingPanel.getGraphics().clearRect(0, 0, jDrawingPanel.getWidth(), jDrawingPanel.getHeight());
            jDrawingPanel.getGraphics().fillRect(10, 10, jDrawingPanel.getWidth() - 20, jDrawingPanel.getHeight() - 20);
        }
    });
    gridBagConstraints = new java.awt.GridBagConstraints();
    gridBagConstraints.gridx = 0;
    gridBagConstraints.gridy = 0;
    gridBagConstraints.fill = java.awt.GridBagConstraints.HORIZONTAL;
    gridBagConstraints.weightx = 0.1;
    gridBagConstraints.insets = new java.awt.Insets(5, 5, 5, 5);
    frame.getContentPane().add(jButtonDrawRect, gridBagConstraints);

    jButtonDrawEllipse.setText("Ellipse");
    jButtonDrawEllipse.addActionListener(new java.awt.event.ActionListener() {
        @Override
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jDrawingPanel.getGraphics().clearRect(0, 0, jDrawingPanel.getWidth(), jDrawingPanel.getHeight());
            jDrawingPanel.getGraphics().fillOval(10, 10, jDrawingPanel.getWidth() - 20, jDrawingPanel.getHeight() - 20);
        }
    });
    gridBagConstraints = new java.awt.GridBagConstraints();
    gridBagConstraints.gridx = 1;
    gridBagConstraints.gridy = 0;
    gridBagConstraints.fill = java.awt.GridBagConstraints.HORIZONTAL;
    gridBagConstraints.weightx = 0.1;
    gridBagConstraints.insets = new java.awt.Insets(5, 5, 5, 5);
    frame.getContentPane().add(jButtonDrawEllipse, gridBagConstraints);
    frame.pack();

    java.awt.EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {
            frame.setVisible(true);
        }
    });
}