public void removeAll() {

        // deregister the collection as a change listener to each series in
        // the collection.
        Iterator iterator = this.data.iterator();
        while (iterator.hasNext()) {
            TaskSeries series = (TaskSeries) iterator.next();
            series.removeChangeListener(this);
        }

        // remove all the series from the collection and notify listeners.
        this.data.clear();
        fireDatasetChanged();