code: public boolean isLocalDateTimeGap(LocalDateTime localDateTime) {
          if (isFixed()) {
              return false;
          }
          try {
              localDateTime.toDateTime(this);
              return false;
          } catch (IllegalInstantException ex) {
              return true;
          }
      }
docs: Checks if the given {@link LocalDateTime} is within a gap.
  <p>
  When switching from standard time to Daylight Savings Time there is
  typically a gap where a clock hour is missing. This method identifies
  whether the local datetime refers to such a gap.
  
  @param localDateTime  the time to check, not null
  @return true if the given datetime refers to a gap
  @since 1.6