protected int[] colsBitsetToIDs(BitSet cols){
  int[] colIDs=new int[cols.cardinality()];
  int colsIndex=0;
  for (int i=cols.nextSetBit(0); i >= 0; i=cols.nextSetBit(i + 1)) {
    colIDs[colsIndex]=i;
    colsIndex++;
  }
  return colIDs;
}

protected int [ ] colsBitsetToIDs ( BitSet cols ) { int [ ] colIDs = new int [ cols . cardinality ( ) ] ; int colsIndex = 0 ; for ( int i = cols . nextSetBit ( 0 ) ; i >= 0 ; i = cols . nextSetBit ( i + 1 ) ) { colIDs [ colsIndex ] = i ; colsIndex ++ ; } return colIDs ; }
convert a bitset into integer column ids .
