If you want logical calendar days, use DAYS.between() method from java.time.temporal.ChronoUnit:
LocalDate dateBefore;
LocalDate dateAfter;
long daysBetween = DAYS.between(dateBefore, dateAfter);
If you want literal 24 hour days, (a duration), you can use the Duration class instead:
LocalDate today = LocalDate.now()
LocalDate yesterday = today.minusDays(1);
// Duration oneDay = Duration.between(today, yesterday); // throws an exception
Duration.between(today.atStartOfDay(), yesterday.atStartOfDay()).toDays() // another option
For more information, refer to this document.
https://stackoverflow.com/questions/27005861/calculate-days-between-two-dates-in-java-8