code: @GwtIncompatible("incompatible method")
      public static long getFragmentInHours(final Calendar calendar, final int fragment) {
          return getFragment(calendar, fragment, TimeUnit.HOURS);
      }
docs: <p>Returns the number of hours within the
  fragment. All datefields greater than the fragment will be ignored.</p>
  
  <p>Asking the hours of any date will only return the number of hours
  of the current day (resulting in a number between 0 and 23). This
  method will retrieve the number of hours for any fragment.
  For example, if you want to calculate the number of hours past this month,
  your fragment is Calendar.MONTH. The result will be all hours of the
  past day(s).</p>
  
  <p>Valid fragments are: Calendar.YEAR, Calendar.MONTH, both
  Calendar.DAY_OF_YEAR and Calendar.DATE, Calendar.HOUR_OF_DAY,
  Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND
  A fragment less than or equal to a HOUR field will return 0.</p>
  
  <ul>
  <li>January 1, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will return 7
  (equivalent to calendar.get(Calendar.HOUR_OF_DAY))</li>
  <li>January 6, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will return 7
  (equivalent to calendar.get(Calendar.HOUR_OF_DAY))</li>
  <li>January 1, 2008 7:15:10.538 with Calendar.MONTH as fragment will return 7</li>
  <li>January 6, 2008 7:15:10.538 with Calendar.MONTH as fragment will return 127 (5*24 + 7)</li>
  <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will return 0
  (a millisecond cannot be split in hours)</li>
  </ul>
  
  @param calendar the calendar to work with, not null
  @param fragment the {@code Calendar} field part of calendar to calculate
  @return number of hours within the fragment of date
  @throws IllegalArgumentException if the date is <code>null</code> or
  fragment is not supported
  @since 2.4