Databases
StackOverflow2013
Postsdbo
POJava Swing text editor throws NullPointerException
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POJava Swing text editor throws NullPointerException
    primarykey
    data
    text
    <p>Alright... I'm starting out with Java and I've stepped up to Swing GUI. Everything was going fine until I tried to work with file input and output.</p> <pre><code> /* ** 'Gooey' GUI in Swing with Java. ** v3 With File Opening */ import javax.swing.*; // Import the swing library import javax.swing.filechooser.*; import java.awt.*; // Import library import java.awt.event.*; // Import event handling import java.io.*; import java.nio.*; import java.nio.charset.*; class gooey implements ActionListener { JFrame myFrame = null; // Create a JFrame, don't fill it JEditorPane myPane = null; String fileName = "myJava.java"; Font editorFont = new Font("Consolas",Font.PLAIN, 12); public static void main(String[] args) { (new gooey()).test(); // Create a GUI and 'test' it } private void test() { // Test run of a gooey // FRAME ////////// System.out.println("Creating myFrame..."); // Debug stuff myFrame = new JFrame("Gooey"); // Create a new JFrame (window) myFrame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); // Set it so that when the [X] button is clicked, the app exits myFrame.setSize(400,300); // Set the size of 400x300px (WxH) System.out.println("myFrame created!"); // Debug stuff // MENU BAR ///////////// System.out.println("Creating menuBar..."); // Debug stuff JMenuBar myBar = new JMenuBar(); // Create a new JMenuBar called myBar System.out.println("Done!"); // More debug stuff System.out.println("Creating JButtons..."); JButton openButton = new JButton("Open"); // Create a button named openButton openButton.addActionListener(this); JButton saveButton = new JButton("Save"); // Create a button named saveButton saveButton.addActionListener(this); JButton quitButton = new JButton("Quit"); // Create a button named quitButton quitButton.addActionListener(this); // Add an actionListener myBar.add(openButton); // Add the buttons to the menubar myBar.add(saveButton); myBar.add(quitButton); System.out.println("Done!"); // Even more debug stuff // EDITOR PANE //////////////// System.out.println("Creating myPane..."); // EVEN MOAR DEBUG JEditorPane myPane = new JEditorPane(); // Create a new JEditorPane called myPane myPane.setContentType("text/plain"); // Set it so that it can only edit plain text myPane.setFont(editorFont); myPane.setText( "This is a JEditorPane." +"\nIt can display text/rich text/HTML that can be edited."); // Set the starting text of myPane to that System.out.println("Done!"); // And yet more debug stuff // RUNNING IT /////////////// System.out.println("Running it all..."); // DEBUG myFrame.setJMenuBar(myBar); // Set the frame's menu bar to myBar myFrame.setContentPane(myPane); // Set it so that the content in myFrame is myPane myFrame.setVisible(true); // Make myFrame visible System.out.println("myFrame has been created!"); } // ACTION LISTENERS ///////////////////// public void actionPerformed(ActionEvent e) { // Basically, every time an action is performed (e.g. left mouse click) // on something with an actionListener attached to it, we can call this // method. if (e.getActionCommand()=="Quit") System.exit(0); // If the string of the thing we're listening to was "quit", exit the program! else { // CREATE A FILE CHOOSER ///////////////////////// JFileChooser myFileChoose = new JFileChooser(); myFileChoose.setCurrentDirectory(new File("C:")); myFileChoose.setSelectedFile(new File(fileName)); myFileChoose.setFileSelectionMode(JFileChooser.FILES_ONLY); FileNameExtensionFilter myFilter = new FileNameExtensionFilter(".java files","java"); myFileChoose.setFileFilter(myFilter); try { // OPEN COMMAND ///////////////// if (e.getActionCommand()=="Open") { int r = myFileChoose.showOpenDialog(myPane); // Create a file chooser if (r == JFileChooser.APPROVE_OPTION) { // If the user has selected a file File selectedFile = myFileChoose.getSelectedFile(); // Find that file fileName = selectedFile.getName(); // Get it's name and store it in a variable FileInputStream fis = new FileInputStream(selectedFile); // Stream the input InputStreamReader isr = new InputStreamReader(fis, Charset.forName("UTF-8")); // Read said stream char[] buffer = new char[1024]; // Create a buffer int n = isr.read(buffer); // Read from the input and buffer String text = new String(buffer, 0, n); // Put into string myPane.setText(text); // Put into JEditorPane isr.close(); } // SAVE COMMAND ///////////////// } else if (e.getActionCommand()=="Save") { int r = myFileChoose.showOpenDialog(myPane); if (r == JFileChooser.APPROVE_OPTION) { // If the user has selected a file File selectedFile = myFileChoose.getSelectedFile(); // Find that file fileName = selectedFile.getName(); // Get it's name and store it in a variable FileOutputStream fos = new FileOutputStream(selectedFile); // Stream the input OutputStreamWriter osr = new OutputStreamWriter(fos, Charset.forName("UTF-8")); // Read said stream osr.write(myPane.getText()); osr.close(); } } } catch (Exception q) { q.printStackTrace(); } } } } </code></pre> <p>I try to make it work, however when I try to open or save a file via a JFileChooser, it shows me these:</p> <p>Open file error:</p> <pre> java.lang.NullPointerException at gooey.actionPerformed(gooey.java:120) </pre> <p>Save file error:</p> <pre> java.lang.NullPointerException at gooey.actionPerformed(gooey.java:132) </pre>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USJoachim Sauer
    1. USTom
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POJava Swing text editor throws NullPointerException
      1. This table or related slice is empty.
      1. VTApproveEditSuggestion
    2. VO
      singulars
      1. POJava Swing text editor throws NullPointerException
      1. This table or related slice is empty.
      1. VTApproveEditSuggestion
    3. VO
      singulars
      1. POJava Swing text editor throws NullPointerException
      1. USClyde Lobo
      1. VTFavorite
    1. COMark lines 120 and 132 in your source code, please.
      singulars
      1. POJava Swing text editor throws NullPointerException
      1. USAndreas_D
    2. COYou need to check if the file exists, File has exists, this will check whether the file exists, if it doesn't you will get a null pointer, it is better that if you are going to use a File IO, that you check to make sure it exits. if (file.exists()){}
      singulars
      1. POJava Swing text editor throws NullPointerException
      1. USJim
    3. COAlso, use .equals() to check equality of `String`s, not `==`.
      singulars
      1. POJava Swing text editor throws NullPointerException
      1. USasgs
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload