having problems with the code mentioned below. the eclipse error code is as follows ::  Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException     at gui.PassengerGui$2.actionPerformed(PassengerGui.java:139)  Any recommendations would be very much appreciated? I have have been pulling my hair out for almost one hour trying to figure out what the problem is..  private JPanel contentPane; private JFileChooser fileChooser; private PassengerController controller; private PassengerTabelPanel tabelPanel; private JTextField nameField; private JTextField cityField; private JTable passengerTable; private JRadioButton  standardRadio; private JRadioButton businessRadio; private ButtonGroup classGroup; private PassengerFormListener formListener;   /**  * Launch the application.  */ public static void main(String[] args) {     EventQueue.invokeLater(new Runnable() {         public void run() {             try {                 PassengerGui frame = new PassengerGui();                 frame.setVisible(true);             } catch (Exception e) {                 e.printStackTrace();             }         }     }); }  /**  * Create the frame.  */ public PassengerGui() {     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);     setBounds(100, 100, 584, 368);      JMenuBar menuBar = new JMenuBar();     setJMenuBar(menuBar);      JMenuItem importDataItem = new JMenuItem("Import Data");     menuBar.add(importDataItem);      JMenuItem exportDataItem = new JMenuItem("Export Data");     menuBar.add(exportDataItem);      fileChooser = new JFileChooser();     fileChooser.addChoosableFileFilter(new PassengerFileFilter());     contentPane = new JPanel();     contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));     setContentPane(contentPane);     contentPane.setLayout(null);      classGroup = new ButtonGroup();      //set up class radio              classGroup.add(standardRadio);             classGroup.add(businessRadio);       JLabel nameLabel = new JLabel("Name: ");     nameLabel.setFont(new Font("Tahoma", Font.PLAIN, 14));     nameLabel.setBounds(12, 11, 69, 31);     contentPane.add(nameLabel);      JLabel cityLabel = new JLabel("City: ");     cityLabel.setFont(new Font("Tahoma", Font.PLAIN, 14));     cityLabel.setBounds(12, 47, 69, 31);     contentPane.add(cityLabel);      JLabel lblNewLabel_2 = new JLabel("Class: ");     lblNewLabel_2.setFont(new Font("Tahoma", Font.PLAIN, 14));     lblNewLabel_2.setBounds(12, 89, 69, 31);     contentPane.add(lblNewLabel_2);      nameField = new JTextField();     nameField.setBounds(60, 18, 129, 20);     contentPane.add(nameField);     nameField.setColumns(10);      cityField = new JTextField();     cityField.setColumns(10);     cityField.setBounds(60, 53, 129, 20);     contentPane.add(cityField);      JRadioButton businessRadio = new JRadioButton("Business");     businessRadio.setBounds(58, 95, 109, 23);     contentPane.add(businessRadio);      JRadioButton standardRadio = new JRadioButton("Standard");     standardRadio.setBounds(60, 127, 109, 23);     contentPane.add(standardRadio);      JButton btnSubmit = new JButton("Submit");     btnSubmit.addActionListener(new ActionListener() {         public void actionPerformed(ActionEvent e) {             String name = nameField.getText();             String city = cityField.getText();             String passengerClass = classGroup.getSelection().getActionCommand();               PassengerFormEvent ev = new PassengerFormEvent(this, name, passengerClass, city);
What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?
Evidence for quantum gravity from gravitational waves The rumor spreads that .  I am far from being an experimentalist, but I want to know if there is any chance that the mentioned observations will reveal any experimental evidence for quantum gravity.  Personally, I feel like this is merely impossible as gravitational waves should propagate in agreement with classical General Relativity. But I might very well not see pitfalls if there are any.  UPDATE: by "evidence for quantum gravity" I mean experimental results which don't agree with predictions of General Relativity or its classical generalizations. They might be coming from string theory or loop gravity or from a completely different approach which we haven't discovered yet. I want to understand what are the chances that new physics will show up during the upcoming  gravitational wave observations.  Also, I expect gravitational waves to be in a highly coherent state, thus making the individual gravitons unobservable. Is this true? List of Ubuntu Versions with Corresponding Linux Kernel Version How can I set the maximum draw type for multiple objects? As a log viewer, which of vim's features are convenient?  less -F is quite good. But I believe vim could be better if we knew its hidden features.     * or #   v//d   g//d   etc..   PS. I don't use vim as a code writing tool. How to handle dynamic changing ID's In XPath? How to Handle Dynamic Changing IDs In XPath? for example :   //div[@id='post-body-3647323225296998740']/div[1]/form[1]/input[1]   In this xpath id "3647323225296998740" is changing every time when reloading the page.   Is there any way to handle this type of situation in Selenium? Why are some faces in my mesh darker? How many String objects will be created when using a plus sign? Proving which QM interpretation is correct Let's assume that the existence of gravitons is theoretically proven or they are detected by LHC could one interpretaion be proven correct? Given two separate annulus with centers $[C_1,C_2]$ and their corresponding radii being $[R_1,r_1]$ and $[R_2,r_2]$ respectively, larger radius being $R$. There are methods to look at whether they are overlapping or not. If they overlap how to find the overlapping area. Is there any close form expression for it?  equation of first annulus   $r_1^2&lt;(x-x_{c1})^2 + (y-y_{c1})^2 &lt;R_1^2$   equation of second annulus  $r_2^2&lt;(x-x_{c2})^2 + (y-y_{c2})^2 &lt;R_2^2$  If there are three circles overlapping, we get overlapping area as solution to set of 4 in-equations by least squares approach(Though we don't end up getting total area but, area within tangents of circles ). For some reasons my brush stroke suddenly looks like this:     As the picture showed, the edges are jagged and pixelated. It doesn't happen before and it's just one of the built-in inking brush.  I know there are a lot of similar questions here but please don't mark this as duplicate. I double checked all the thing the other answers suggested: It's brush tool, not pencil, and my mode of brush and layer is Normal, not Dissolve. It's pixelated even if I draw with mouse so it's not tablet driver issue. I disabled GPU render but nothing changed. How do I fix this? How do I suppress the "New release '12.10' available" message? Is it possible to run three versions of Google Chrome? How might I run 3+ versions of google chrome so I can log into to 3 different google accounts.  More specifically I am looking to have separate icons in the dock for the 3 separate running applications.  How might I run duplicate and or copy versions of the same application.  The following  by Mark works for a lot of applications but not for Google Chrome.  It appears the following might work . Javascript Closures and 'this' I have a problem with an object I have created that looks something like this:  var myObject = {      AddChildRowEvents: function(row, p2) {         if(document.attachEvent) {             row.attachEvent('onclick', function(){this.DoSomething();});         } else {             row.addEventListener('click', function(){this.DoSomething();}, false);         }     },      DoSomething: function() {         this.SomethingElse(); //&lt;-- Error here, object 'this' does not support this method.     } }   The problem is that when I am inside the 'DoSomething' function, 'this' does not refer to 'myObject' what am I doing wrong? self referential struct definition? Unexpected Results From Clicking The Unanswered Button I've tried to render my scene but there's an object that won't show up. I've checked the camera, I've checked the visibility, it isn't hidden and it's showing in the viewport. I feel like I've opened every setting and have achieved nothing. I’m trying to render a book with a cover, flipping pages and stacks of pages. I have no idea how to fix the fact that the book cover doesn’t render. If I create a plane and select both the book cover and the plane and join them with Ctrl+J, the render contains a book cover but it doesn’t turn as it’s rigged to do so because it’s now linked to the plane and loses all the animated properties. As soon as I unjoin them the book cover stops rendering and everything appears as you see it there, a book with binding, pages, but no cover. For the life of me I cannot figure out what’s going on. There's a link to the file here: I've just finished running my first session with only one player, and it felt pretty different from running a session for a group.  Could someone with more experience in this talk about what one should do differently in that situation?  I'm not referring to mechanics like encounter-building, but just how to handle the change to the social dynamics. How can I get merit points? I want to advance in the ranks of Senator Lavigny-Duval. How can I get merit points? I know I can participate in expansion goals, but is there a better way than that? C# and USB HID Devices Can it be proven in $\sf ZF^{\neg\infty}$ that the sets $x_n=\{x_{n+1}\}$ do not exist?