#vulnerable code 
                                public static void main(String[] args) {
        final JFrame frame = new JFrame();
        final Provider provider = Provider.getCurrentProvider();

        provider.init();
        final JTextField textField = new JTextField();
        textField.setEditable(false);
        textField.addKeyListener(new KeyAdapter() {
            @Override
            public void keyPressed(KeyEvent e) {
                if (MODIFIERS.contains(e.getKeyCode()))
                    textField.setText("");
                else
                    textField.setText(KeyStroke.getKeyStrokeForEvent(e).toString().replaceAll("pressed ", ""));
            }
        });
        frame.add(textField, BorderLayout.CENTER);
        JPanel box = new JPanel(new GridLayout(2, 1));
        JButton grab = new JButton("Grab");
        box.add(grab);
        final HotKeyListener listener = new HotKeyListener() {
            public void onHotKey(final HotKey hotKey) {
                SwingUtilities.invokeLater(new Runnable() {
                    public void run() {
                        JOptionPane.showMessageDialog(frame, "Hooray: " + hotKey);
                    }
                });
            }
        };
        grab.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String text = textField.getText();
                if (text != null && text.length() > 0) {
                    provider.reset();
                    provider.register(KeyStroke.getKeyStroke(text), listener);
                }
            }
        });

        JButton grabMedia = new JButton("Grab media keys");
        grabMedia.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                provider.register(MediaKey.MEDIA_NEXT_TRACK, listener);
                provider.register(MediaKey.MEDIA_PLAY_PAUSE, listener);
                provider.register(MediaKey.MEDIA_PREV_TRACK, listener);
                provider.register(MediaKey.MEDIA_STOP, listener);
            }
        });
        box.add(grabMedia);


        frame.add(box, BorderLayout.PAGE_END);

        frame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                provider.reset();
                provider.stop();
                System.exit(0);
            }
        });

        frame.setSize(300, 150);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public static void main(String[] args) {
        final JFrame frame = new JFrame();
        final Provider provider = Provider.getCurrentProvider(true);

        final JTextField textField = new JTextField();
        textField.setEditable(false);
        textField.addKeyListener(new KeyAdapter() {
            @Override
            public void keyPressed(KeyEvent e) {
                if (MODIFIERS.contains(e.getKeyCode()))
                    textField.setText("");
                else
                    textField.setText(KeyStroke.getKeyStrokeForEvent(e).toString().replaceAll("pressed ", ""));
            }
        });
        frame.add(textField, BorderLayout.CENTER);
        JPanel box = new JPanel(new GridLayout(2, 1));
        JButton grab = new JButton("Grab");
        box.add(grab);
        final HotKeyListener listener = new HotKeyListener() {
            public void onHotKey(final HotKey hotKey) {
                JOptionPane.showMessageDialog(frame, "Hooray: " + hotKey);
            }
        };
        grab.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String text = textField.getText();
                if (text != null && text.length() > 0) {
                    provider.reset();
                    provider.register(KeyStroke.getKeyStroke(text), listener);
                }
            }
        });

        JButton grabMedia = new JButton("Grab media keys");
        grabMedia.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                provider.register(MediaKey.MEDIA_NEXT_TRACK, listener);
                provider.register(MediaKey.MEDIA_PLAY_PAUSE, listener);
                provider.register(MediaKey.MEDIA_PREV_TRACK, listener);
                provider.register(MediaKey.MEDIA_STOP, listener);
            }
        });
        box.add(grabMedia);


        frame.add(box, BorderLayout.PAGE_END);

        frame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                provider.reset();
                provider.stop();
                System.exit(0);
            }
        });

        frame.setSize(300, 150);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }