docs: public boolean get(int index) {
          int i = index >> 6;               // div 64
          // signed shift will keep a negative index and force an
          // array-index-out-of-bounds-exception, removing the need for an explicit check.
          if (i>=bits.length) return false;
  
          int bit = index & 0x3f;           // mod 64
          long bitmask = 1L << bit;
          return (bits[i] & bitmask) != 0;
      }