code: public static LongTuple zero(int size)
      {
          if (size >= 0 && size < ZERO_POOL_SIZE)
          {
              return ZEROS[size];
          }
          return createZero(size);
      }
docs: Returns a tuple with the specified size, containing
  all zeros.
  
  @param size The size
  @return The zero tuple.
  @throws IllegalArgumentException If the size is smaller than 0