private WeekFields(DayOfWeek firstDayOfWeek,int minimalDaysInFirstWeek){
  Objects.requireNonNull(firstDayOfWeek,"firstDayOfWeek");
  if (minimalDaysInFirstWeek < 1 || minimalDaysInFirstWeek > 7) {
    throw new IllegalArgumentException("Minimal number of days is invalid");
  }
  this.firstDayOfWeek=firstDayOfWeek;
  this.minimalDays=minimalDaysInFirstWeek;
}

private WeekFields ( DayOfWeek firstDayOfWeek , int minimalDaysInFirstWeek ) { Objects . requireNonNull ( firstDayOfWeek , "firstDayOfWeek" ) ; if ( minimalDaysInFirstWeek < 1 || minimalDaysInFirstWeek > 7 ) { throw new IllegalArgumentException ( "Minimal number of days is invalid" ) ; } this . firstDayOfWeek = firstDayOfWeek ; this . minimalDays = minimalDaysInFirstWeek ; }
creates an instance of the definition .
