public synchronized void undo() throws CannotUndoException {  }
public synchronized void undo() throws CannotUndoException { if (!isInProgress()) { super.undo(); return; }  UndoableEdit edit = editToBeUndone(); if (edit == null) throw new CannotUndoException();  undoTo(edit); }
	public synchronized void undo() throws CannotUndoException {		// TODO	} // undo()