code: public boolean getBit(int index)
      {
          assertValidIndex(index);
          int word = index / WORD_LENGTH;
          int offset = index % WORD_LENGTH;
          return (data[word] & (1 << offset)) != 0;
      }
docs: Returns the bit at the specified index.
  @param index The index of the bit to look-up (0 is the least-significant bit).
  @return A boolean indicating whether the bit is set or not.
  @throws IndexOutOfBoundsException If the specified index is not a bit
  position in this bit string.