Bug 323444 [Undo] [Commands] java.util.ConcurrentModificationException when trying to get the undo history from a source viewer
I got the following exception once when attempting to get the undo history from a source viewer in my code. Looking at the implementation of this method, I cannot seem to see how this could occur since all access to this list in DefaultOperationHistory are synchronized. Maybe it is the creation of the iterator outside of the synchronized block? Note that I have been unable to reproduce this since I first saw it since it seems to be a rare race condition. Exception Stack Trace: java.util.ConcurrentModificationException at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372) at java.util.AbstractList$Itr.next(AbstractList.java:343) at org.eclipse.core.commands.operations.DefaultOperationHistory.filter(DefaultOperationHistory.java:558) at org.eclipse.core.commands.operations.DefaultOperationHistory.getUndoHistory(DefaultOperationHistory.java:843)
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/DefaultOperationHistory.java
*/
	private void internalRemove(IUndoableOperation operation) {
		operation.dispose();
		notifyRemoved(operation);
	}
	/*
	 * Notify listeners of an operation event.
	 */
	private void notifyListeners(final OperationHistoryEvent event) {
		if (event.getOperation() instanceof IAdvancedUndoableOperation) {
			final IAdvancedUndoableOperation advancedOp = (IAdvancedUndoableOperation) event
					.getOperation();
			SafeRunner.run(new ISafeRunnable() {
				public void handleException(Throwable exception) {
					if (DEBUG_OPERATION_HISTORY_UNEXPECTED) {
						Tracing
								.printTrace(
										"OPERATIONHISTORY", 
										"Exception during notification callback " + exception); 
					}
				}
				public void run() throws Exception {
					advancedOp.aboutToNotify(event);
				}
			});
		}
		final Object[] listenerArray = listeners.getListeners();
		for (int i = 0; i < listenerArray.length; i++) {
			final IOperationHistoryListener listener = (IOperationHistoryListener) listenerArray[i];
			SafeRunner.run(new ISafeRunnable() {