public String undo(){
  if (!canUndo()) {
    return "";
  }
  UndoAction undoAction=m_undoStack.get(m_nCurrentEditAction);
  m_bNeedsUndoAction=false;
  undoAction.undo();
  m_bNeedsUndoAction=true;
  m_nCurrentEditAction--;
  return undoAction.getUndoMsg();
}

public String undo ( ) { if ( ! canUndo ( ) ) { return "" ; } UndoAction undoAction = m_undoStack . get ( m_nCurrentEditAction ) ; m_bNeedsUndoAction = false ; undoAction . undo ( ) ; m_bNeedsUndoAction = true ; m_nCurrentEditAction -- ; return undoAction . getUndoMsg ( ) ; }
undo the last edit action performed on the network . returns message representing the action performed .
