Calculate a Time Based on Known Date Plus Decimal Hours

[Steve Dyke]

I need to generate a calculated finish time based on a known start date and the hours spent to complete it.

My code works good unless the hours spent are less than 1 or the hours have a fraction.

public HoursCalculator(String seedDate, float hours){
		
		Calendar cal = Calendar.getInstance();
		try{
			cal.setTime(new SimpleDateFormat("MM/dd/yyyy HH:mm").parse(seedDate));
		}
		catch(ParseException pe){
			System.out.println("HoursCalculator2: "+pe);
		}
		
		cal.add(Calendar.HOUR, (int)hours);
				
		SimpleDateFormat formatter = new SimpleDateFormat("HH:mm");
		
		ehours = formatter.format(cal.getTime());
			
	}

[Norm Radder]

unless the hours spent are less than 1 or the hours have a fraction.

How would you calculate the end date if you did it by hand? The Calendar class can add units of time besides hours. Can you convert the non-integer hours to some other time units?

[Tony Docherty]

If you are using Java 8 you may want to look at the new java.time API which makes it so much easier to handle times.