code: public static long requirePositive(long l, String message) {
      Objects.requireNonNull(message, "message must not be null");
  
      if (l <= 0) {
        throw new IllegalArgumentException(message);
      }
  
      return l;
    }
docs: Requires that a {@code long} is greater than zero.
  
  @param l the {@code long} to test
  @param message detail message to be used in the event that a {@link IllegalArgumentException}
  is thrown
  @return the {@code long} if greater than zero
  @throws IllegalArgumentException if {@code l} is less than or equal to zero