Bug 127861 [DataBinding] Mark API provisional
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/viewers/TreeViewerDescription.java
if (columns!=null && columns.size()>columnIndex)
		   return (Column) columns.get(columnIndex);
		return null;
	}
	
	/**
	 * @param instanceType
	 * @param column
	 * @return column's index, or -1 if it is not a valid column
	 */
	public int getColumnIndex(Class instanceType, Column column) {
		List columns = (List) columnsMap.get(instanceType);
		if (columns!=null)
			return columns.indexOf(column);
		return -1;
	}
	/**
	 * @return treeViewer
	 */
	public TreeViewer getTreeViewer() {
		return treeViewer;
	}
	
	public Class[] getClassTypes() {
		if (columnsMap.keySet().size()==0) return null;
		
		return (Class[]) columnsMap.keySet().toArray(new Class[columnsMap.keySet().size()]);
	}
}