Error when trying to export a JTable to an Excel file

Question

I'm trying to export a JTable to an Excel file but I always run into a similar error with each site and forum I visited.

Here's where I call the function: (Commented important lines)

try {
        exportTable(table, new File("C:\\Test\\TA\\Data\\tables.xls")); //THIS IS LINE 99
    } catch (IOException e1) {
            
        e1.printStackTrace();
    }

Here's where the function is:

Line 220 code is similar to a lot of different methods I've tried but is always the one that seems to cause the errors and after testing I still can't find the solution.

public void exportTable(JTable table, File file) throws IOException {
        TableModel model = table.getModel();
        FileWriter out = new FileWriter(file);
        for(int i=0; i < model.getColumnCount(); i++) {
    out.write(model.getColumnName(i) + "\t");
        }
        out.write("\n");

        for(int i=0; i< model.getRowCount(); i++) {
    for(int j=0; j < model.getColumnCount(); j++) {
        out.write(model.getValueAt(i,j).toString()+"\t"); //THIS IS LINE 220
        }
        out.write("\n");
    }

    out.close();
    System.out.println("write out to: " + file);
}

And I always get the same error with whatever variant of this I try:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at testing.TableExample2.exportTable(TableExample2.java:220)
    at testing.TableExample2$4.actionPerformed(TableExample2.java:99)
    at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
    at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308)
    at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
    at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
    at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
    at java.desktop/java.awt.Component.processMouseEvent(Component.java:6631)
    at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
    at java.desktop/java.awt.Component.processEvent(Component.java:6396)
    at java.desktop/java.awt.Container.processEvent(Container.java:2263)
    at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5007)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4839)
    at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4918)
    at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4547)
    at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4488)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307)
    at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2772)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4839)
    at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
    at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
    at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
    at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

The message is telling your a variable on line 220 is null. Figure out which variable is null and then fix the problem. Just use a System.out.println(...) on every variable in the line to determine which is null. This is basic debugging. We can't tell you which variable is null. I would guess the `model.getValueAt(...)` method is returning a null value so you can't invoke toString() on the value. — camickr, Sep 03 '20 at 00:57
1) See [What is a stack trace, and how can I use it to debug my application errors?](http://stackoverflow.com/q/3988788/418556) & [What is a Null Pointer Exception, and how do I fix it?](http://stackoverflow.com/q/218384/418556) 2) For better help sooner, [edit] to add a [MCVE] or [Short, Self Contained, Correct Example](http://www.sscce.org/). — Andrew Thompson, Sep 12 '20 at 14:07

Error when trying to export a JTable to an Excel file

0 Answers0