code: public static WeekDay getDay(final int calDay) {
          WeekDay day = null;
          switch (calDay) {
              case Calendar.SUNDAY:
                  day = SU;
                  break;
              case Calendar.MONDAY:
                  day = MO;
                  break;
              case Calendar.TUESDAY:
                  day = TU;
                  break;
              case Calendar.WEDNESDAY:
                  day = WE;
                  break;
              case Calendar.THURSDAY:
                  day = TH;
                  break;
              case Calendar.FRIDAY:
                  day = FR;
                  break;
              case Calendar.SATURDAY:
                  day = SA;
                  break;
              default:
                  break;
          }
          return day;
      }
docs: Returns the corresponding day constant to the specified
  java.util.Calendar.DAY_OF_WEEK property.
  @param calDay a property value of java.util.Calendar.DAY_OF_WEEK
  @return a string, or null if an invalid DAY_OF_WEEK property is
  specified