Best way to check if timespan of different persons overlapps or not [closed]

Posted on


My current implementation,

 class Person {
    int id;
    String name;
    LocalDate start;
    LocalDate end;
    /*getters and setters*/

    private void checkForTimespanOverlaps(List<Person> persons)
    final int totalPersons = superiorSalesAgentHasFunctionDTOs.size();
    LocalDate[][] timespans = new LocalDate[totalPersons][2];
    int row = 0;
    for (Person person : persons)
        timespans[row][0] = person.getStartDate();
        timespans[row][1] = person.getEndDate();

    // sort timespans array
    LocalDate[][] sortedTimespans = sortTimespan(timespans);
    for (int row = 0; row < sortedTimespans.length - 1; row++)
         if ((sortedTimespans[row][1].isAfter(sortedTimespans[row + 1][0])))
          //there is overlap as previous person's endDate is after next person's startDate

private LocalDate[][] sortTimespan(LocalDate[][] timespans)
    Arrays.sort(timespans, new Comparator<LocalDate[]>()
        public int compare(LocalDate[] startDates, LocalDate[] endDates)
            LocalDate startDate = startDates[0];
            LocalDate endDate = endDates[0];
            return startDate.compareTo(endDate);
    return supervisionTimespans;

Is it Good solution?

or how can it be Refactored and make Clean Code?


You’re doing way too much work here. You don’t need the arrays at all.

First, write a Comparator<Person>. It’s better off in its own class so it can be reused later.

import java.util.Comparator;

final class TimespanComparator implements Comparator<Person> {

    public int compare(final Person person1, final Person person2) {
        return person1.getStartDate().compareTo(person2.getEndDate());

Then sort a new copy of the List<Person> using that comparator. Walk through the sorted list to do your comparison. You can start the loop at index 1 because if there’s only 1 person, there can’t be any overlap and the loop will never get entered.

private void checkForTimespanOverlaps(final List<Person> persons) {
    final List<Person> sortedList = new ArrayList<>(persons);
    Collections.sort(sortedList, new TimespanComparator());

    for (int i = 1; i < sortedList.size(); i++) {
        final LocalDate priorEndTime = sortedList.get(i - 1).getEndDate();
        final LocalDate currentStartTime = sortedList.get(i).getStartDate();
        if (priorEndTime.isAfter(currentStartTime)) {
            // ...

As an aside, American english uses ‘people’ as the plural of person, not persons. Americans might prefer to see the variable named people instead.

Leave a Reply

Your email address will not be published. Required fields are marked *