There are couple of methods with no API comments in javax.swing.updo.UndoableEditSupport. I think beginUpdate() and endUpdate() are important for this class so please add method description for these. endUpdate actually has comments but it's a warning and not telling what this method does.
http://java.sun.com/javase/6/docs/api/javax/swing/undo/UndoableEditSupport.html#beginUpdate()
http://java.sun.com/javase/6/docs/api/javax/swing/undo/UndoableEditSupport.html#endUpdate()