code: @GwtIncompatible("incompatible method")
      public static long getFragmentInMilliseconds(final Date date, final int fragment) {
          return getFragment(date, fragment, TimeUnit.MILLISECONDS);
      }
docs: <p>Returns the number of milliseconds within the
  fragment. All datefields greater than the fragment will be ignored.</p>
  
  <p>Asking the milliseconds of any date will only return the number of milliseconds
  of the current second (resulting in a number between 0 and 999). This
  method will retrieve the number of milliseconds for any fragment.
  For example, if you want to calculate the number of milliseconds past today,
  your fragment is Calendar.DATE or Calendar.DAY_OF_YEAR. The result will
  be all milliseconds of the past hour(s), minutes(s) and second(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 SECOND field will return 0.</p>
  
  <ul>
  <li>January 1, 2008 7:15:10.538 with Calendar.SECOND as fragment will return 538</li>
  <li>January 6, 2008 7:15:10.538 with Calendar.SECOND as fragment will return 538</li>
  <li>January 6, 2008 7:15:10.538 with Calendar.MINUTE as fragment will return 10538 (10*1000 + 538)</li>
  <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will return 0
  (a millisecond cannot be split in milliseconds)</li>
  </ul>
  
  @param date the date to work with, not null
  @param fragment the {@code Calendar} field part of date to calculate
  @return number of milliseconds within the fragment of date
  @throws IllegalArgumentException if the date is <code>null</code> or
  fragment is not supported
  @since 2.4