Re: any recommendations?
Knute Johnson wrote:
Brandon McCombs wrote:
Hello,
Somewhere in my code I have a bug that I can't reliably reproduce. It
occurs randomly when I'm deleting entries from a JList (I retrieve
certain pieces of info from the entry before deleting it, then I
delete it and the JList contents are then refreshed so remaining items
are re-added to the JList). The only output I get when the exception
occurs is the following:
Exception in thread "AWT-EventQueue-0"
java.lang.ArrayIndexOutOfBoundsException: 1 >= 0
at java.util.Vector.elementAt(Unknown Source)
at javax.swing.DefaultListModel.getElementAt(Unknown Source)
at javax.swing.plaf.basic.BasicListUI.paintCell(Unknown Source)
at javax.swing.plaf.basic.BasicListUI.paint(Unknown Source)
[snip]
The "1" as the index value differs between exception printouts. I
don't know where that index value is originating from or what Vector
is really having its elements retrieved. The index value doesn't
correspond to the index of the Object that I'm selecting for deletion.
I've placed try/catches throughout the places where I thought was
causing the exception to print out a stacktrace that I hoped would
include a line number but I'm not getting any extra output. I also
would put in a print statement so I knew which try/catch was being
executed but I don't see that outputted either.
When the JList is refreshed it is done so through a thread. I've tried
to use run() to make the thread do its work but not in a thread and I
don't get the exception but since I can't reproduce it reliably I
don't know if it's really a threading problem or not. Using Eclipse's
debugger also doesn't help so far because I can't get the error to
occur during the debugging, at least not yet.
Is there anything else I can try that can give me more information as
to what line in my code this is occurring on so I can begin to fix it?
thanks
Are you modifying the JList on the EDT? Are you modifying the Vector
after creating your JList? Can you make a simple test program that
demonstrates the problem?
The code that the Thread class uses to tell the JList when to update is
this:
SwingUtilities.invokeLater(new Runnable() {
public void run() {
component.updateGUI(results);
component.resetGUI(results);
}
});
Component is the class that contains my GUI which is a JTree and JList
in a JSplitPane; component is passed into the Thread's constructor.
Results is a Vector that contains the results of a LDAP search which
will be put into the JList.
Yes I'm modifying the Vector. Since the JList can have entries
added/modified/removed the Vector will obviously be changed accordingly
(as I state in the original mesg). I can't make a simple test program
because I don't know where the problem is. If I did I wouldn't have
posted this because I'd be working on figuring out a way to fix it. The
problem could be in a lot of places and ripping out stuff to duplicate
the problem would be a waste of time I believe since I can't reproduce
it not to mention the code involved is spread across multiple classes.
To test it I'm having to create temporary entries in my LDAP server and
then delete them one by one to see if the error occurs. Sometimes I
delete 50 before it crops up, other times I delete 1 and the index value
mentioned in the exception never corresponds with the deleted entry.
I'm mainly asking if there is a way to glean more info from the
exception information. I can't believe it isn't giving me a line number
to review. Is the printout I originally posted the only stack trace
information available from the JVM? I've put whole method bodies in a
try/catch and I don't get any more information so either I won't get
more information or I'm putting try/catches in the wrong place. Can the
JVM be launched with options that will help?
Brandon