why do we get AssertionFailedError?

Question

I have the following piece of code:

        TableViewer tv = new TableViewer(attributeTable);
        tv.setContentProvider(new BOAttributeTableContentProvider());
        tv.setLabelProvider(new BOAttributeTableLabelProvider());

where while setting the label provider i am getting AssertionFailedError. can anybody tell me what wrong i am doing here? or in which case it throws this error?

error Log:

org.eclipse.jface.util.Assert$AssertionFailedException: null argument;
    at org.eclipse.jface.util.Assert.isNotNull(Assert.java:150)
    at org.eclipse.jface.util.Assert.isNotNull(Assert.java:126)
    at org.eclipse.jface.viewers.StructuredViewer.disassociate(StructuredViewer.java:615)
    at org.eclipse.jface.viewers.TableViewer.internalRefreshAll(TableViewer.java:904)
    at org.eclipse.jface.viewers.TableViewer.internalRefresh(TableViewer.java:818)
    at org.eclipse.jface.viewers.TableViewer.internalRefresh(TableViewer.java:807)
    at org.eclipse.jface.viewers.StructuredViewer$7.run(StructuredViewer.java:1388)
    at org.eclipse.jface.viewers.StructuredViewer.preservingSelection(StructuredViewer.java:1323)
    at org.eclipse.jface.viewers.StructuredViewer.refresh(StructuredViewer.java:1386)
    at org.eclipse.jface.viewers.StructuredViewer.refresh(StructuredViewer.java:1345)
    at org.eclipse.jface.viewers.ContentViewer.setLabelProvider(ContentViewer.java:281)
    at org.eclipse.jface.viewers.StructuredViewer.setLabelProvider(StructuredViewer.java:2003)
    at org.eclipse.jface.viewers.TableViewer.setLabelProvider(TableViewer.java:1086)
    at com.misys.bankfusion.bpdesigner.boeditor.pages.BOAttributesPage.populateAttributeTableContents(BOAttributesPage.java:458)
    at com.misys.bankfusion.bpdesigner.boeditor.pages.BOAttributesPage.access$000(BOAttributesPage.java:128)
    at com.misys.bankfusion.bpdesigner.boeditor.pages.BOAttributesPage$1.setToModel(BOAttributesPage.java:341)
    at com.trapedza.bankfusion.editor.AbstractEditorDelegate.updateData(AbstractEditorDelegate.java:173)
    at com.trapedza.bankfusion.editor.AbstractEditorDelegate$1.dialogFieldChanged(AbstractEditorDelegate.java:181)
    at com.trapedza.bankfusion.utils.dialogs.internal.DialogField.dialogFieldChanged(DialogField.java:132)
    at com.trapedza.bankfusion.utils.dialogs.internal.ListBoxDialogField.doModifySelection(ListBoxDialogField.java:51)
    at com.trapedza.bankfusion.utils.dialogs.internal.ComboDialogField$2.widgetSelected(ComboDialogField.java:153)
    at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:90)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:66)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:928)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3348)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:2968)
    at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:1930)
    at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:1894)
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:422)
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
    at org.eclipse.ui.internal.ide.IDEApplication.run(IDEApplication.java:95)
    at org.eclipse.core.internal.runtime.PlatformActivator$1.run(PlatformActivator.java:78)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:92)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:68)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:400)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:177)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:585)
    at org.eclipse.core.launcher.Main.invokeFramework(Main.java:336)
    at org.eclipse.core.launcher.Main.basicRun(Main.java:280)
    at org.eclipse.core.launcher.Main.run(Main.java:977)
    at org.eclipse.core.launcher.Main.main(Main.java:952)

Answer 1

Constructor that you are using (TableViewer) or two setters (setContentProvider, setLabelProvider) have guarding assert statements which are throwing these exceptions. Author of the code had an idea to protect its code from irregular parameters that you are using when invoking her/his code.

Answer 2

The stack trace shows that your call to 'TableViewer.setLabelProvider()' from 'BOAttributesPage.populateAttributeTableContents()' eventually results in call to 'org.eclipse.jface.viewers.StructuredViewer.disassociate()' with null argument and that method constraints input argument to be not-null.

Answer 3

It looks like BOAttributeTableContentProvider provides a null object somewhere along line (one of the elements you are trying to display in the table is null). Debug the content provider. Hope my late answer will help.