The method findNextDayPart produces an infinite loop if the date in the argument has its hours and minutes outisde of business hours. This can be fixed by the following change:
public DayPart findNextDayPart(Date date) {
DayPart nextDayPart = null;
while(nextDayPart==null) {
nextDayPart = findDayPart(date);
if (nextDayPart==null)

{ date = findStartOfNextDay(date); Object result[] = new Object[2]; Day day = findDay(date); day.findNextDayPartStart(0, date, result); nextDayPart = (DayPart) result[1]; }

}
return nextDayPart;
}

Furthermore the method isInBusinessHours is wrongly implemented; the use of findNextDayPart would always lead to a result of true (if findNextDayPart would work). This failure can be fixed as follows:

public boolean isInBusinessHours(Date date)

{ return (findDayPart(date)!=null); }