code: Long getValue(TemporalField field) {
          try {
              return temporal.getLong(field);
          } catch (DateTimeException ex) {
              if (optional > 0) {
                  return null;
              }
              throw ex;
          }
      }
docs: Gets the value of the specified field.
  <p>
  This will return the value for the specified field.
  
  @param field  the field to find, not null
  @return the value, null if not found and optional is true
  @throws DateTimeException if the field is not available and the section is not optional