question: public void undo ( ) { if ( -- m_tempUndoIndex < 0 ) { m_tempUndoIndex = m_tempUndoFiles . length - 1 ; } if ( m_tempUndoFiles [ m_tempUndoIndex ] != null ) { AbstractFileLoader loader = ConverterUtils . getLoaderForFile ( m_tempUndoFiles [ m_tempUndoIndex ] ) ; try { loader . setFile ( m_tempUndoFiles [ m_tempUndoIndex ] ) ; setInstancesFromFile ( loader ) ; } catch ( Exception e ) { e . printStackTrace ( ) ; m_Log . logMessage ( e . toString ( ) ) ; JOptionPane . showMessageDialog ( PreprocessPanel . this , "Cannot perform undo operation!\n" + e . toString ( ) , "Undo" , JOptionPane . ERROR_MESSAGE ) ; } m_tempUndoFiles [ m_tempUndoIndex ] = null ; } int temp = m_tempUndoIndex - 1 ; if ( temp < 0 ) { temp = m_tempUndoFiles . length - 1 ; } m_UndoBut . setEnabled ( m_tempUndoFiles [ temp ] != null ) ; }
target:  Reverts to the last backed up version of the dataset.