Comparing Date and Time with three days ahead using Java-8 LocaldateTime

Question

I have a java application where in the User can not modify the order after a specific date and time.eg.the user can not modify the order after the 3rd day by 12:00 PM,say if the order was placed on Nov 9th,the user will not be able to modify the oder after Nov 12th,12:00 PM.The Date is Dynamic but the time is very much static.

I was trying to use the below logic to calculate this and i am unable to figure out how to extract the current time from LocalDateTime.now() for comparison.

final LocalDate orderDate  =orderData.getOrderDate.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();
final LocalDate currentDate = LocalDate.now();
final LocalDateTime currentDateTime = LocalDateTime.now();
final LocalDate orderCancellationCutOffDate = 
orderDate.minusDays(orderCancellationCutOffDays);

if (currentDate.equals(orderCancellationCutOffDays) && 
currentDateTime.isBefore(<12:00 PM>)){

<Business rule>
    }   

Can anyone help me with an efficient way to do this comparison.

Answer 1

Only if you know for sure that your program will never be used outside your own time zone, is it safe to use LocalDateTime . I receommend you use ZonedDateTime just in case.

In any case, using that LocalDateTime , the code for your logic as I have understood it is:

final int orderCancellationCutOffDays = 3;
final LocalTime orderCancellationCutOffTime = LocalTime.of(12, 0);

LocalDate orderDate = LocalDate.of(2019, Month.NOVEMBER, 6);
LocalDateTime orderCancellationCutOffDateTime
        = orderDate.plusDays(orderCancellationCutOffDays)
                .atTime(orderCancellationCutOffTime);
final LocalDateTime currentDateTime = LocalDateTime.now(ZoneId.of("America/Punta_Arenas"));
if (currentDateTime.isAfter(orderCancellationCutOffDateTime)) {
    System.out.println("This order can no longer be modified.");
} else {
    System.out.println("You can still modify this order,");
}

Of course substitute your own time zone where I put America/Punta_Arenas .

Answer 2

Suppose if you have the oder date in LocalDate as today

LocalDate orderDate //2019-11-09

Now create the deadline date by adding 3 days to it

LocalDateTime deadLineDate =orderDate.plusDays(3).atStartOfDay(); //2019-11-12T00:00

Even if you want a particular time you can use atTime methods

LocalDateTime deadLineDate =orderDate.plusDays(3).atTime(12,0);

So if currentDateTime is before the deadLineDate customer can modify the order

if(currentDateTime.isBefore(deadLineDate)) {
    // can modify the order

    }
else {
   //user can not modify the order
}