ConcurrentModificationException

[Guest]

Sorry if this is a known issue but shouldn't the use of

new java.util.ArrayList() in a number of places be

List list = Collections.synchronizedList(new ArrayList(...));

in accordance with http://java.sun.com/j2se/1.4.2/docs/api/index.html in order to be thread-safe (for the publically accessible data. also need to synchronized(data) too.)

I get a number of exceptions at runtime especially with respect to the rendering of the CategoryPlot.


Thanks for listening. And keep up the good work.

[mhilpert]

Me too. But interestingly they only appear if I display a chart on a gui. I f I just create a chart and save it, it didn't happen so far.

[david.gilbert]

Please post the exceptions and any pointers on how to reproduce the problem.

[Guest]

This is one exception I got (running 0.9.21)

[java] java.util.ConcurrentModificationException
[java] at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:448)
[java] at java.util.AbstractList$Itr.next(AbstractList.java:419)
[java] at java.util.Collections$1.next(Collections.java:996)
[java] at java.util.Collections$1.next(Collections.java:996)
[java] at org.jfree.chart.axis.CategoryAxis.refreshTicks(CategoryAxis.java:788)
[java] at org.jfree.chart.axis.CategoryAxis.drawCategoryLabels(CategoryAxis.java:653)
[java] at org.jfree.chart.axis.CategoryAxis.draw(CategoryAxis.java:617)
[java] at org.jfree.chart.plot.CategoryPlot.drawAxes(CategoryPlot.java:1996)
[java] at org.jfree.chart.plot.CategoryPlot.draw(CategoryPlot.java:1869)
[java] at org.jfree.chart.plot.Plot.draw(Plot.java:725)
[java] at org.jfree.chart.JFreeChart.draw(JFreeChart.java:904)
[java] at org.jfree.chart.ChartPanel.paintComponent(ChartPanel.java:999)
[java] at javax.swing.JComponent.paint(JComponent.java:808)
[java] at javax.swing.JComponent.paintWithOffscreenBuffer(JComponent.java:4787)
[java] at javax.swing.JComponent.paintDoubleBuffered(JComponent.java:4740)
[java] at javax.swing.JComponent._paintImmediately(JComponent.java:4685)
[java] at javax.swing.JComponent.paintImmediately(JComponent.java:4488)
[java] at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:410)
[java] at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:117)
[java] at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:178)
[java] at java.awt.EventQueue.dispatchEvent(EventQueue.java:454)
[java] at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:201)
[java] at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
[java] at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:145)
[java] at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:137)
[java] at java.awt.EventDispatchThread.run(EventDispatchThread.java:100)


On 1.0.rc1, I got a different exception:
[java] Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
[java] at org.jfree.chart.renderer.xy.StackedXYAreaRenderer.drawItem(StackedXYAreaRenderer.java:488)
[java] at org.jfree.chart.plot.XYPlot.render(XYPlot.java:2590)
[java] at org.jfree.chart.plot.XYPlot.draw(XYPlot.java:2168)
[java] at org.jfree.chart.JFreeChart.draw(JFreeChart.java:1058)
[java] at org.jfree.chart.ChartPanel.paintComponent(ChartPanel.java:1271)
[java] at javax.swing.JComponent.paint(JComponent.java:1003)
[java] at javax.swing.JComponent.paintChildren(JComponent.java:840)
[java] at javax.swing.JComponent.paint(JComponent.java:1012)
[java] at javax.swing.JComponent.paintChildren(JComponent.java:840)
[java] at javax.swing.JComponent.paint(JComponent.java:1012)
[java] at javax.swing.JComponent.paintWithOffscreenBuffer(JComponent.java:4930)
[java] at javax.swing.JComponent.paintDoubleBuffered(JComponent.java:4883)
[java] at javax.swing.JComponent._paintImmediately(JComponent.java:4826)
[java] at javax.swing.JComponent.paintImmediately(JComponent.java:4633)
[java] at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:451)
[java] at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:114)
[java] at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
[java] at java.awt.EventQueue.dispatchEvent(EventQueue.java:461)
[java] at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:234)
[java] at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
[java] at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
[java] at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
[java] at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)

[david.gilbert]

The second one is a bug that is fixed in CVS. Do you have any hints on how to reproduce the first? What does your code do leading up to the exception?

[Guest]

Here's more info.

I noticed that it occurs more often running on Redhat Linux than Windows.
Maybe it's the JVM?

The JVM on Linux is:
java version "1.4.2_05"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_05-b04)
Java HotSpot(TM) Client VM (build 1.4.2_05-b04, mixed mode)

The JVM on Windows 2000 Professional is:
java version "1.5.0_01"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_01-b08)
Java HotSpot(TM) Client VM (build 1.5.0_01-b08, mixed mode)


Anyway, most of the time it's running correctly and my codes don't automatically trigger the exception. From the exception, it looks like that it's triggered by Swing's main rendering thread.

My codes is basically having a ChartPanel inside a Swing panel. Data series continuously streaming in and I just add them one at a time to the dataset (DefaultCategoryDataset).

BTW, It works fine for all the other data types (PieDataset, DefaultTableXYDataset, XYSeriesCollection)... just not CategoryDataset...

[skunk]

My codes is basically having a ChartPanel inside a Swing panel. Data series continuously streaming in and I just add them one at a time to the dataset (DefaultCategoryDataset).

Swing is not thread safe. Are you adding the new data points from the correct thread?

[Guest]

I guess I don't understand what you meant by "correct thread". Do you mean to say that there are certain restrictions on which thread can add a data series to a dataset?

Could you clarify what you meant. Which threads are the wrong threads to add data and which particular thread is "the correct thread" to add data?

In my codes, there's a separate daemon thread (aside from the ui thread) running in the background that add another data series as they come in... So, are you saying that this thread shouldn't be adding data to the dataset?

[Taqua]

Hi,

for all Swing applications it can be said, that operations that might cause updates to GUI components must be executed on the Event-Dispatcher thread. To post update code on that thread, you could wrap your code into a java.lang.Runnable object and use SwingUtilities.invokeAndWait(..) (suspends the caller thread until the runnable has been completly executed) or SwingUtilities.invokeLater(..) (Asynchronous call, order of the calls is guaranteed).

Have mo' fun,
said Thomas

[Guest]

Ah, ok. thanks.

I did that in other parts of the codes but I never thought I have to do that with respect to JFreeChart. I always thought that it will handle everything for me.

I guess I will have to wrap it a bit.
I'll give it a try and see if the exception go away.

Thanks everyone...

[tduraipkt]

java.lang.NullPointerException
at org.jfree.chart.axis.CategoryAxis.createLabel(CategoryAxis.java:821)
at org.jfree.chart.axis.CategoryAxis.refreshTicks(CategoryAxis.java:789)
at org.jfree.chart.axis.CategoryAxis.reserveSpace(CategoryAxis.java:542)
at org.jfree.chart.plot.CategoryPlot.calculateDomainAxisSpace(CategoryPlot.java:1746)
at org.jfree.chart.plot.CategoryPlot.calculateAxisSpace(CategoryPlot.java:1809)
at org.jfree.chart.plot.CategoryPlot.draw(CategoryPlot.java:1853)
at org.jfree.chart.plot.Plot.draw(Plot.java:725)
at org.jfree.chart.JFreeChart.draw(JFreeChart.java:904)
at org.jfree.chart.JFreeChart.createBufferedImage(JFreeChart.java:1037)
at org.jfree.chart.JFreeChart.createBufferedImage(JFreeChart.java:1020)
at org.jfree.chart.ChartUtilities.writeChartAsPNG(ChartUtilities.java:156)
at de.laures.cewolf.util.Renderer.handlePNG(Renderer.java:137)
at de.laures.cewolf.util.Renderer.renderChart(Renderer.java:105)
at de.laures.cewolf.util.Renderer.render(Renderer.java:85)
at de.laures.cewolf.taglib.ChartImageDefinition.ensureRendered(ChartImageDefinition.java:139)
at de.laures.cewolf.taglib.ChartImageDefinition.getBytes(ChartImageDefinition.java:133)
at de.laures.cewolf.storage.SerializableChartImage.(SerializableChartImage.java:49)
at de.laures.cewolf.storage.FileStorage.storeChartImage(FileStorage.java:86)
at de.laures.cewolf.taglib.tags.ChartImgTag.doStartTag(ChartImgTag.java:79)


Hai ,
this is the exception i got when using cewolf........
Give me the solution..........

regards,
Durai.....

[oacis]

Hai ,
this is the exception i got when using cewolf........
Give me the solution..........

Hello,

It is going to be a little bit difficult to give you the solution without first understanding what the problem is. I may be able to help 'guide' you to the correct resolution though...

What versions of JFreeChart and cewolf are you using?

If you are using the latest 1.0.1 JFreeChart then the offending line of code is:

Code: Select all

x0 = getCategoryStart(categoryIndex, ticks.size(), 
     dataArea, edge);

I would recommend that you have a look at the 'ticks' object and whether there is a way to set this in cewolf so that it is not null.