code: public void setCivil(boolean beCivil)
      {
          civil = beCivil;
  
          if (beCivil && cType != CalculationType.ISLAMIC_CIVIL) {
              // The fields of the calendar will become invalid, because the calendar
              // rules are different
              long m = getTimeInMillis();
              cType = CalculationType.ISLAMIC_CIVIL;
              clear();
              setTimeInMillis(m);
          } else if(!beCivil && cType != CalculationType.ISLAMIC) {
              // The fields of the calendar will become invalid, because the calendar
              // rules are different
              long m = getTimeInMillis();
              cType = CalculationType.ISLAMIC;
              clear();
              setTimeInMillis(m);
          }
      }
docs: Determines whether this object uses the fixed-cycle Islamic civil calendar
  or an approximation of the religious, astronomical calendar.
  
  @param beCivil   <code>true</code> to use the civil calendar,
  <code>false</code> to use the astronomical calendar.
  @apiNote <strong>Discouraged:</strong> ICU 57 use setCalculationType(CalculationType) instead
  @hide unsupported on Android