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Finding empty Calender date slots [duplicate]

This question already has answers here:
Determine Whether Two Date Ranges Overlap
(39 answers)
Closed 8 years ago.
I have two date ranges, (start1,end1):::>>date1 && (start2,end2):::>>date2 .
I want to check if the two dates isOverLaped.
My flow chart I assume "<>=" operators is valid for comparing.
boolean isOverLaped(Date start1,Date end1,Date start2,Date end2) {
if (start1>=end2 && end2>=start2 && start2>=end2) {
return false;
} else {
return true;
}
}
Any Suggestion will be appreciated.

You can use Joda-Time for this.
It provides the class Interval which specifies a start and end instants and can check for overlaps with overlaps(Interval).
Something like
DateTime now = DateTime.now();
DateTime start1 = now;
DateTime end1 = now.plusMinutes(1);
DateTime start2 = now.plusSeconds(50);
DateTime end2 = now.plusMinutes(2);
Interval interval = new Interval( start1, end1 );
Interval interval2 = new Interval( start2, end2 );
System.out.println( interval.overlaps( interval2 ) );
prints
true
since the end of the first interval falls between the start and end of the second interval.

boolean overlap(Date start1, Date end1, Date start2, Date end2){
return start1.getTime() <= end2.getTime() && start2.getTime() <= end1.getTime();
}

//the inserted interval date is start with fromDate1 and end with toDate1
//the date you want to compare with start with fromDate2 and end with toDate2
if ((int)(toDate1 - fromDate2).TotalDays < 0 )
{ return true;}
else
{
Response.Write("<script>alert('there is an intersection between the inserted date interval and the one you want to compare with')</script>");
return false;
}
if ((int)(fromDate1 - toDate2).TotalDays > 0 )
{ return true;}
else
{
Response.Write("<script>alert('there is an intersection between the inserted date interval and the one you want to compare with')</script>");
return false;
}

You have two intervals, i1 and i2. There are six cases for how the intervals can be temporally related (at least in a Newtonian world view) but only two are important: if i1 is entirely before i2 or i1 is entirely after i2; otherwise the two intervals are overlapping (the other four cases are i1 contains i2, i2 contains i1, i1 contains the start of i2 and i1 contains the end of i2). Assume i1 and i2 are of type Interval that have Date fields beginTime and endTime. The function then is (note, the assumption here is that if i1 starts at the same time i2 ends, or vice versa, we don't consider that an overlap and we assme for a given interval endTime.before(beginTime) is false):
boolean isOverlapped(Interval i1, Interval i2) {
return i1.endTime.before(i2.beginTime) || i1.beginTime.after(i2.endTime);
}
In the original question, you specify DateTime instead of Date. In java, Date has both date and time. This is in contrast to sql where Date does not have a time element while DateTime does. That is a point of confusion that I stumbled across when I first started using sql after having done only java for many years. Anyway, I hope this explanation is helpful.

Java 8 Time API / Is current time in time frame [duplicate]

Please suggest if there is an API support to determine if my time is between 2 LocalTime instances, or suggest a different approach.
I have this entity:
class Place {
LocalTime startDay;
LocalTime endDay;
}
which stores the working day start and end time, i.e. from '9:00' till '17:00', or a nightclub from '22:00' till "5:00".
I need to implement a Place.isOpen() method that determines if the place is open at a given time.
A simple isBefore/isAfter does not work here, because we also need to determine if the end time is on the next day.
Of course, we can compare the start and end times and make a decision, but I want something without additional logic, just a simple between() call. If LocalTime is not sufficient for this purpose, please suggest other.

If I understand correctly, you need to make two cases depending on whether the closing time is on the same day as the opening time (9-17) or on the next day (22-5).
It could simply be:
public static boolean isOpen(LocalTime start, LocalTime end, LocalTime time) {
if (start.isAfter(end)) {
return !time.isBefore(start) || !time.isAfter(end);
} else {
return !time.isBefore(start) && !time.isAfter(end);
}
}

This looks cleaner for me:
if (start.isBefore(end)) {
return start.isBefore(date.toLocalTime()) && end.isAfter(date.toLocalTime());
} else {
return date.toLocalTime().isAfter(start) || date.toLocalTime().isBefore(end);
}

I have refactored #assylias answer so i use int instead of local time as i get open and close hour from api int integer format
public static boolean isOpen(int start, int end, int time) {
if (start>end) {
return time>(start) || time<(end);
} else {
return time>(start) && time<(end);
}
}
public static boolean isOpen(int start, int end) {
SimpleDateFormat sdf = new SimpleDateFormat("HH");
Date resultdate = new Date();
String hour = sdf.format(resultdate);
int time = Integer.valueOf(hour);
if (start>end) {
return time>(start) || time<(end);
} else {
return time>(start) && time<(end);
}
}

Check whether a given Instant fits a defined Period

What we get is an Instant and a "date-grid" defined by a period (which defines the interval of datapoints, e.g.: Every Month, Every 3 Months, etc.) and a start date where we started that grid.
private Instant getValidDate(Instant request, Instant start, Period period) {
if(isOnGrid(request, start, period)) {
return request;
}
else {
return getNextPriorDateOnGrid(request, start, period);
}
}
An example:
Given are the following parameters:
request = Instant("2000-05-02T07:42:00.000Z") //Second May of 2000 7:42 AM
start = Instant("2000-01-01T06:00:00.000Z") //First January of 2000 6:00 AM
period = Period("3M") //Every 3 Months
isOnGrid(request, start, period); //Should return false
getNextPriorDate(request, start, period) //Should return the First April of 2000 6:00 AM
I really have no idea how to get this with reasonable performance (its a critical place in code)
How do you check whether a distant future date (given by the Instant) is exactly on this grid, and if not, what is the next past date that was on the grid?
EDIT: I forgot to mention: All times and dates are assumed to be in UTC Timezone

Here is a simple test case that should match your requirements:
package test;
import java.time.Duration;
import java.time.Instant;
import java.time.LocalDateTime;
import java.time.Period;
import java.time.ZoneId;
public class Java8PeriodAndInstant2 {
public static void main(String[] args) {
// LocalDate request=LocalDate.of(2000, 5, 2);
// LocalDate start=LocalDate.of(2000, 1, 1);
LocalDateTime start = Instant.parse("2000-01-01T06:00:00.000Z").atZone(ZoneId.of("UTC")).toLocalDateTime();
LocalDateTime request = Instant.parse("2000-05-02T07:42:00.000Z").atZone(ZoneId.of("UTC")).toLocalDateTime();
Period period = Period.ofMonths(3);
System.out.println("is on grid " + isOnGrid(request, start, period));
System.out.println("is on grid " + isOnGrid(LocalDateTime.of(2000, 4, 2,0,0), start, period));
System.out.println("is on grid " + isOnGrid(LocalDateTime.of(2000, 4, 1,0,0), start, period));
System.out.println("getNextPriorDate " + getNextPriorDate(request, start, period));
System.out.println("isOnGrid " + isOnGrid(Instant.parse("2000-01-03T05:00:00.000Z").atZone(ZoneId.of("UTC")).toLocalDateTime(), start, Period.ofDays(1)));
System.out.println("isOnGrid " + isOnGrid(Instant.parse("2000-01-03T06:00:00.000Z").atZone(ZoneId.of("UTC")).toLocalDateTime(), start, Period.ofDays(1)));
System.out.println("getNextPriorDate " + getNextPriorDate(Instant.parse("2000-01-03T05:00:00.000Z").atZone(ZoneId.of("UTC")).toLocalDateTime(), start, Period.ofDays(1)));
}
private static boolean isOnGrid(LocalDateTime start, LocalDateTime request, Period period) {
if (period.getDays() != 0) {
return ((Duration.between(start, request).toHours()%period.getDays())==0);
}
Period diffPeriod = Period.between(start.toLocalDate(), request.toLocalDate());
if (diffPeriod.getDays()!=0) {
return false;
}
if (period.getMonths() != 0) {
return ((diffPeriod.toTotalMonths()) % (period.toTotalMonths()) == 0);
}
if (diffPeriod.getMonths()!=0) {
return false;
}
if (period.getYears() != 0) {
return ((diffPeriod.getYears()) % (period.getYears()) == 0);
}
return false;
}
private static LocalDateTime getNextPriorDate(LocalDateTime request, LocalDateTime start, Period period) {
if (period.getDays() != 0) {
long hoursDiff=Duration.between(start, request).toHours();
return start.plusDays(hoursDiff/24);
}
Period diffPeriod = Period.between(start.toLocalDate(), request.toLocalDate());
if (period.getMonths() != 0) {
diffPeriod = diffPeriod.withDays(0);
long monthDiff = diffPeriod.toTotalMonths() % period.toTotalMonths();
return start.plus(diffPeriod).minusMonths(monthDiff);
}
if (period.getYears() != 0) {
diffPeriod = diffPeriod.withDays(0);
diffPeriod.withMonths(0);
long yearsDiff = diffPeriod.getYears() % period.getYears();
return start.plus(diffPeriod).minusYears(yearsDiff);
}
return null;
}
}
it works with periods of days or months or years.

You cannot add Periods to Instants. They have a different "scope".
An Instant i simply represents a point in the timeline, counting the amount of millis/nanos from a specific point in time called "Epoch".
At this instant i, the time at the clock at the wall (even the date in a calendar) differs around the world. It depends on the timezone you are in.
A Period respects different lengths of its representation among different timezones starting at differnt dates. For example: A month lasts 30 days in June but 31 days in August. And it is even more complex if daylight saving shifts occur.
An Instant has no idea, what a "month" actually is. You can parse it from a String and output it to it, but internally it does not represent a human understandable form of a month like 'Jan', 'Feb', ... .
This is, why you have to align an Instant to a LocalDateTime or ZonedDateTime using a ZoneId or an ZoneOffset. Theses classes understand and can work with Periods.
The following code converts your Instants to LocalDateTimes to take into account the above comments:
private static Instant getValidDate2(Instant request, Instant start, Period period)
{
assert(!request.isBefore(start));
// multiplication of period only works with days exclusive or
// zero daypart of period
assert(period.getDays() == 0 || (period.getMonths() == 0 && period.getYears() == 0));
ZoneId utcZone = ZoneOffset.UTC;
LocalDateTime ldstart = LocalDateTime.ofInstant(start, utcZone);
LocalDateTime ldreq = LocalDateTime.ofInstant(request, utcZone);
// calculate an approximation of how many periods have to be applied to get near request
Duration simpleDuration = Duration.between(ldstart, ldstart.plus(period));
Duration durationToReq = Duration.between(ldstart, ldreq);
int factor = (int) (durationToReq.toDays() / simpleDuration.toDays()); // rough approximation
// go near to request by a multiple of period
Period jump = Period.of(period.getYears() * factor, period.getMonths() * factor, period.getDays() * factor);
LocalDateTime ldRunning = ldstart.plus(jump);
// make sure ldRunning < request
while (ldRunning.isAfter(ldreq)) {
ldRunning = ldRunning.minus(period);
}
// make sure we pass request and
// save the the last date before or equal to request on the grid
LocalDateTime ldLastbefore = ldRunning;
while (!ldRunning.isAfter(ldreq)) {
ldLastbefore = ldRunning;
ldRunning = ldRunning.plus(period);
}
return ldLastbefore.equals(ldreq) ? request : ldLastbefore.atZone(utcZone).toInstant();
}
Explanation:
To avoid a loop adding period until it gets to request, a rough approximation is done on how often period must be added to start to come to request. A new period being a multiple of the request period is then added and aligned to get the last value of the grid which is less or equal to request. Depending on a comparation between the last value and request, the according instant is returned. In fact, the check is useless besides the fact, that request == request when it was on the grid and not only equal.
Here you can find further informations about java time: https://docs.oracle.com/javase/tutorial/datetime/overview/index.html

get count back of DateTime that where within the correct range - Joda Time

I want to get the count back of DateTime that where within the correct range with Joda Time.
I have this version at the moment which is only good to check for a specific day:
public int getIntFatalitiesAtDay(DateTime AtDay) {
int resultCount = 0;
for( Fatality f : fatalities) {
if(Days.daysBetween(f.date, AtDay).getDays() == 0) {
resultCount++;
}
}
return resultCount;
}
This was usefull when i looped threw every day. However now i go by months with:
for (DateTime iDate = fa.firstDate; iDate.isBefore(fa.lastDate); iDate = iDate.plusMonths(1)) { ... }
And now i would like to get the count of fatalities that month.
Could someone help?
(Also from that year, althought i would like to see a option aswell where it doesn't look at the year but that's less important.)

Java's java.util.Date class has methods for determining if one date is before or after another. If you convert the DateTime objects to Date objects, you can do:
if (f.date.after(beginngingDate) && f.date.before(endingDate)).

How would I go about finding the closest date to a specified date? (Java)

I was hoping to know how I would type up a method to give me the closest date to a specified date. What I mean is something along the following:
public Date getNearestDate(List<Date> dates, Date currentDate) {
return closestDate // The date that is the closest to the currentDate;
}
I have found similar questions, but only one had a good answer and the code kept giving me NullPointerExceptions ...
Can anyone help me?

You can solve in linear time by computing the difference in time (e.g. Date#getTime()) and returning the minimum:
public static Date getNearestDate(List<Date> dates, Date currentDate) {
long minDiff = -1, currentTime = currentDate.getTime();
Date minDate = null;
for (Date date : dates) {
long diff = Math.abs(currentTime - date.getTime());
if ((minDiff == -1) || (diff < minDiff)) {
minDiff = diff;
minDate = date;
}
}
return minDate;
}
[Edit]
Minor performance improvements.

Use Date#getTime and substract the values. The smallest result will be your closest date.

Order the list by order of dates and perform a dichotomic search. Remember that to compare the dates you can use Date.getTime() to get the date as milliseconds, which are usually easier to compare.

You would order the dates by the closest.
Have a start date set to 0:
long ret = 0;
Now you need to loop though your list and keep the closest to your desired date
for(Date d : dates){
if(Math.abs(curDate.getTime() - ret) > Math.abs(curDate.getTime() - d.getTime())){
ret = d.getTime();
}
}
return new Date(ret);
The if statement checks which date is closer by comparing the millisecond time. By using Math.abs, you eliminate direction (before or after).