Print Datetime between Two timestamps in Java-CodePudding

Here is my requirement. Pretty sure there is an elegant way to do this. Need your help. I need to build a backend program to process and insert multiple dates into a table using start and end time selected by user.

Input:

StartTime: 11/26/2021 11:00 PM
EndTime: 11/28/2021 04:00 AM

Output I am expecting

11/26/2021 11:00 PM
11/26/2021 11:59 PM
11/27/2021 12:00 AM
11/27/2021 11:59 PM
11/28/2021 12:00 AM
11/28/2021 04:00 AM

My Code

public static void main(String[] args) {
        
        String StartTime = "11/27/2021 11:00 PM";
        String EndTime = "11/29/2021 04:00 AM";
        
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MM/dd/yyyy hh:mm a");
        LocalDate localStartDate = LocalDate.parse(StartTime, formatter);
        LocalDate localEndDate = LocalDate.parse(EndTime, formatter);

        LocalDateTime  localStartTime = LocalDateTime.parse(StartTime,formatter);
        LocalDateTime  localEndTime = LocalDateTime.parse(EndTime,formatter);
        
        
        List<LocalDateTime> totalDates = new ArrayList<>();
        while (!localStartTime.isAfter(localEndTime)) {
            totalDates.add(localStartTime);
            totalDates.add(localStartTime.with(LocalTime.MAX));
            localStartTime = localStartTime.plusDays(1);
            localStartTime = localStartTime.with(LocalTime.MIN);
        }
        
        totalDates.add(localEndTime.with(LocalTime.MIN));
        totalDates.add(localEndTime);
        
        for (int i = 0; i < totalDates.size(); i  ) {
            System.out.print(totalDates.get(i)   "\n");
        }

    }

My Output:

2021-11-27T23:00
2021-11-27T23:59:59.999999999
2021-11-28T00:00
2021-11-28T23:59:59.999999999
2021-11-29T00:00
2021-11-29T23:59:59.999999999
2021-11-29T00:00
2021-11-29T04:00

CodePudding user response：

You also need to parse the output. Therefore you can use the already defined DateTimeFormatter, which has a parse method.

Code for the output:

System.out.println(totalDates.get(i).format(formatter));

Also you have one additional line in your output. This one comes from the line where you set localStartTime = localStartTime.with(LocalTime.MIN);. Here i would suggest this change:

LocalDateTime workingStartTime = localStartTime;

List<LocalDateTime> totalDates = new ArrayList<>();
while (!workingStartTime.isAfter(localEndTime)) {
  if(!workingStartTime.equals(localStartTime)) {
    workingStartTime = workingStartTime.with(LocalTime.MIN);
  }
  totalDates.add(workingStartTime);
  totalDates.add(workingStartTime.with(LocalTime.MAX));
  workingStartTime = workingStartTime.plusDays(1);
}

Edit: Solution using streams and flatMap

Here is how you build the final List with streams (no extra adding of the last day is needed):

List<LocalDateTime> totalDates = localStartTime.toLocalDate().datesUntil(localEndTime.toLocalDate().plusDays(1))
    .flatMap(date -> Stream.of(
        date.equals(localStartTime.toLocalDate()) ? LocalDateTime.of(date, localStartTime.toLocalTime()) : LocalDateTime.of(date, LocalTime.MIN),
        date.equals(localEndTime.toLocalDate()) ? LocalDateTime.of(date, localEndTime.toLocalTime()) : LocalDateTime.of(date, LocalTime.MAX))
    )
    .collect(Collectors.toList());

CodePudding user response：

This seems to work. If there are other elegant ways to do this.. Please let me know.

public static void main(String[] args) {

    String StartTime = "02/27/2021 11:00 PM";
    String EndTime = "03/02/2021 01:00 PM";

    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MM/dd/yyyy hh:mm a");
    LocalDate localStartDate = LocalDate.parse(StartTime, formatter);
    LocalDate localEndDate = LocalDate.parse(EndTime, formatter);

    LocalDateTime localStartTime = LocalDateTime.parse(StartTime, formatter);
    LocalDateTime localEndTime = LocalDateTime.parse(EndTime, formatter);

    List<LocalDateTime> totalDates = new ArrayList<>();
    while (localEndDate.isAfter(localStartDate)) {

        totalDates.add(localStartTime);
        totalDates.add(localStartTime.with(LocalTime.MAX));

        if (!localStartDate.equals(localEndDate)) {
            localStartTime = localStartTime.plusDays(1).with(LocalTime.MIN);
        }
        localStartDate = localStartDate.plusDays(1);

    }

    totalDates.add(localEndTime.with(LocalTime.MIN));
    totalDates.add(localEndTime);

    for (int i = 0; i < totalDates.size(); i  ) {
        System.out.print(formatter.format(totalDates.get(i))   "\n");
    }
}

CodePudding user response：

String startTime = "11/26/2021 11:00 PM";
String endTime = "11/28/2021 04:00 AM";

DateTimeFormatter dtf =
        DateTimeFormatter.ofPattern("MM/dd/yyyy hh:mm a");
LocalDateTime start = LocalDateTime.parse(startTime, dtf);
LocalDateTime end = LocalDateTime.parse(endTime, dtf);

Start streaming the dates as given
then create an inner stream by creating two LocalDateTime instances using the current LocalDate instance.
- current datetime by 1 minute before midnight
- current datetime by 1 day ahead of midnight
then flatMap that stream and put the datetimes in a linked list.
to finish, add the current start LocalDateTime to the beginning of the list
and the ending LocalDateTime to the end of the list

List<LocalDateTime> list =
        start.toLocalDate().datesUntil(end.toLocalDate())
                .flatMap(date -> Stream.of(
                        date.atTime(23,59),
                        date.atTime(0,0).plusDays(1)))
                .collect(Collectors
                        .toCollection(LinkedList::new));
list.add(0, start);
list.add(end);
list.forEach(d -> System.out.println(d.format(dtf)));

prints

11/26/2021 11:00 PM
11/26/2021 11:59 PM
11/27/2021 12:00 AM
11/27/2021 11:59 PM
11/28/2021 12:00 AM
11/28/2021 04:00 AM