question: public void addGroupedColumn ( int columnIndex ) { int [ ] [ ] newColGroups = getColumnGroups ( ) ; if ( newColGroups . length == 0 ) { newColGroups = new int [ ] [ ] { { columnIndex } } ; } else { int lastGroupIndex = newColGroups . length - 1 ; int [ ] lastGroup = newColGroups [ lastGroupIndex ] ; int groupSize = lastGroup . length ; int [ ] newLastGroup = new int [ groupSize + 1 ] ; System . arraycopy ( lastGroup , 0 , newLastGroup , 0 , groupSize ) ; newLastGroup [ groupSize ] = columnIndex ; newColGroups [ lastGroupIndex ] = newLastGroup ; } setColumnGroups ( newColGroups ) ; }
target:  Adds the specified column index to the last column group. In case there are no groups, a new group will be created.