Date comparison with apex performance

Question

Working on a component in which fromdate and toDate are added inside salesforce.

Criteria is something like any new from/end date should not be a part of precious record present in List. Tried to add code like :

if((new Date(userStartDate) >= new Date(StartDateVal)) && (new Date(userStartDate)<= new Date(EndDateVal)))
            {add error
}
else if((new Date(endDate) >= new Date(StartDateVal)) && (new Date(endDate)<=new Date(EndDateVal)))
            { add error
}

Is there any better way of comparing including usage of Maps etc

Answer 1

For small-ish lists, you can use the DateRange class.

public class DateRange {
    DateTime begins, ends;
    public DateRange(DateTime b, DateTime e) {
        begins = b;
        ends = e;
    }
    public Integer hashCode() {
        return 1;
    }
    public Boolean equals(Object o) {
        DateRange r = (DateRange)o;
        return begins < r.ends && ends > r.begins;
    }
}

To use it:

Set<DateRange> ranges = new Set<DateRange>();
for(Integer index = 0, size = inputs.size(); index < size; index++) {
  DateRange key = new DateRange(startDates[index], endDates[index]);
  if(ranges.contains(key)) {
    // record an error for this index;
  } else {
    ranges.add(key);
  }
}

Note that because of how this class operates, if you add a range when contains returns true, it will screw up the internal state of the Set/Map. However, it will perform decently well on lists of up to a few hundred items.

This algorithm is an exponential-growth algorithm, specifically average is n²/2 executions, and max executions is n². I've tested this up to about 1,000 items without a problem, though.

It's much faster than the manual:

for(Integer i = 0, s = items.size(); i < s; i++) {
  for(Integer j = i + 1; j < s; j++) {
    ...
  }
}

If you can, do this validation in JavaScript, it's much more efficient.