code: public void remove(BitSet other)
      {
          int idx = Math.min(wlen, other.wlen);
          long [] thisArr = this.bits;
          long [] otherArr = other.bits;
          while (--idx >= 0)
          {
              thisArr[idx] &= ~otherArr[idx];
          }
      }
docs: Remove all elements set in other: this = this AND_NOT other
  @param other The other bitset.