Extract gaps from a List of Range<Date>

Question

I have a list of Range<Date> based on the Guava library, they never overlap.

• 2001-01-10 → 2001-01-15
• 2001-01-20 → 2001-01-22
• 2001-01-28 → 2001-01-29

Then, I have a reference range:

• 2001-01-01 → 2001-01-31

I want to find all the exclusive gaps between the list and the reference range:

• 2001-01-01 → 2001-01-10
• 2001-01-15 → 2001-01-20
• 2001-01-22 → 2001-01-28
• 2001-01-29 → 2001-01-31

For this example, the Date objects are simple, but in reality they may vary in format depending on their ChronoUnit.

Is there a right way to get this result without too much coding?

Answer 1

My approach would be something like

RangeSet<Date> rangeSet = TreeRangeSet.create();
rangeSet.add(referenceRange);
for (Range<Date> range : rangesToRemove) {
  rangeSet.remove(range);
}
for (Range<Date> exclusiveRange : rangeSet.asRanges()) {
   ...
}

If you manipulate the range bounds correctly, you should get them in the format you desire.