java.lang.NullPointerException I can't find my error as to why

Question

I am getting a NullPointerException when running the following example:

private void contractExpiryActionPerformed(java.awt.event.ActionEvent evt) {                                               
   String expireDate = contractExpiry.getSelectedItem().toString();
   System.out.println(expireDate);

}

Just want to printout the date to test if it is working, But I keep getting this error no matter what I do.

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at tetrapro.IncomeSolution.contractExpiryActionPerformed(IncomeSolution.java:865)
    at tetrapro.IncomeSolution.lambda$initComponents$6(IncomeSolution.java:492)
    at javax.swing.JComboBox.fireActionEvent(JComboBox.java:1258)
    at javax.swing.JComboBox.contentsChanged(JComboBox.java:1332)
    at javax.swing.JComboBox.intervalRemoved(JComboBox.java:1352)
    at javax.swing.AbstractListModel.fireIntervalRemoved(AbstractListModel.java:179)
    at javax.swing.DefaultComboBoxModel.removeAllElements(DefaultComboBoxModel.java:174)
    at javax.swing.JComboBox.removeAllItems(JComboBox.java:771)
    at tetrapro.IncomeSolution.setExpirationDates(IncomeSolution.java:250)
    at tetrapro.IncomeSolution.(IncomeSolution.java:61)
    at tetrapro.IncomeSolution.lambda$main$11(IncomeSolution.java:1007)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

contractExpiry is a JcomboBox. I know what a nullPointerException is. I have no idea why it is showing up in my code. It doesn't make any sense. I have the eventListener in the constructor but I always get this error when I want to get the item selected. — Philip Caputo, Oct 22 '16 at 16:27

score 1 · Answer 1 · answered Oct 28 '16 at 14:31

1

Most likely contractExpiry is null getSelectedItem() returns null. Use your IDE's debugging option and palce a breakpoint on the 3rd line of your sample code

OR

private void contractExpiryActionPerformed(java.awt.event.ActionEvent evt) {
   System.out.println("contractExpiry = " + contractExpiry);
   System.out.println("contractExpiry.getSelectedItem() = " + contractExpiry.getSelectedItem());

   String expireDate = contractExpiry.getSelectedItem().toString();
   System.out.println(expireDate);

}

This actually shows you where the NullPointerException occurs:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at tetrapro.IncomeSolution.contractExpiryActionPerformed(IncomeSolution.java:865)

answered Oct 28 '16 at 14:31

Viorel Florian

594
9
29

1

I got it figured out. Thank you – Philip Caputo Oct 28 '16 at 21:11
Was there no item selected? – Viorel Florian Oct 29 '16 at 17:54
1

I made the method take a parameter then it solved it. – Philip Caputo Oct 30 '16 at 02:11
Post the solution, with a short description as an answer to properly close the issue, in case anyone finds this and has similar problems – Viorel Florian Oct 30 '16 at 16:40

score 1 · Answer 2 · answered Oct 31 '16 at 01:12

 private void displayOptions(String symbol){
    int count = contractExpiry.getItemCount();

    if(count != 0){
        String expire = contractExpiry.getSelectedItem().toString();        
        x = expire.substring(expire.length()-5, expire.length());
        days = data.getDaysToExpire(symbol, x);

        displayNumDays.setText(days);

        data.getSelectedData_F(symbol, x);
    }

    String last = data.getFuturePrice(contractBox.getSelectedIndex());
    displayPrice.setText(last);

I had to test if the jcombobox was empty or not. when it was empty it was giving me the error. Now, if the item count is 0 it will be skip. Hence, no more error. Thanks everyone for your help.

java.lang.NullPointerException I can't find my error as to why

2 Answers2