public DataSet toDataSetV() {
        final int rowLength = rowLength();
        final int columnLength = columnLength();
        final List<String> dataSetColumnNameList = new ArrayList<>(rowLength);

        for (R rowKey : _rowKeySet) {
            dataSetColumnNameList.add(N.toString(rowKey));
        }

        final List<List<Object>> dataSetColumnList = new ArrayList<>(rowLength);

        if (_initialized) {
            for (int i = 0; i < rowLength; i++) {
                final List<Object> column = new ArrayList<>(columnLength);

                for (int j = 0; j < columnLength; j++) {
                    column.add(_columnList.get(j).get(i));
                }

                dataSetColumnList.add(column);
            }
        } else {
            for (int i = 0; i < rowLength; i++) {
                List<Object> column = new ArrayList<>(columnLength);
                N.fill(column, 0, columnLength, null);
                dataSetColumnList.add(column);
            }
        }

        return new RowDataSet(dataSetColumnNameList, dataSetColumnList);
    }
public DataSet toDataSetV ( ) { final int rowLength = rowLength ( ) ; final int columnLength = columnLength ( ) ; final List < String > dataSetColumnNameList = new ArrayList < > ( rowLength ) ; for ( R rowKey : _rowKeySet ) { dataSetColumnNameList . add ( N . toString ( rowKey ) ) ; } final List < List < Object > > dataSetColumnList = new ArrayList < > ( rowLength ) ; if ( _initialized ) { for ( int i = 0 ; i < rowLength ; i ++ ) { final List < Object > column = new ArrayList < > ( columnLength ) ; for ( int j = 0 ; j < columnLength ; j ++ ) { column . add ( _columnList . get ( j ) . get ( i ) ) ; } dataSetColumnList . add ( column ) ; } } else { for ( int i = 0 ; i < rowLength ; i ++ ) { List < Object > column = new ArrayList < > ( columnLength ) ; N . fill ( column , 0 , columnLength , null ) ; dataSetColumnList . add ( column ) ; } } return new RowDataSet ( dataSetColumnNameList , dataSetColumnList ) ; }
@return a DataSet based on column.