question: @ Override public void undo ( ) { File tempFile ; Instances inst ; ObjectInputStream ooi ; if ( canUndo ( ) ) { tempFile = m_UndoList . get ( m_UndoList . size ( ) - 1 ) ; try { ooi = new ObjectInputStream ( new BufferedInputStream ( new FileInputStream ( tempFile ) ) ) ; inst = ( Instances ) ooi . readObject ( ) ; ooi . close ( ) ; setInstances ( inst ) ; notifyListener ( new TableModelEvent ( this , TableModelEvent . HEADER_ROW ) ) ; notifyListener ( new TableModelEvent ( this ) ) ; } catch ( Exception e ) { e . printStackTrace ( ) ; } tempFile . delete ( ) ; m_UndoList . remove ( m_UndoList . size ( ) - 1 ) ; } }
target:  undoes the last action