Null safe date comparator for sorting in Java 8 Stream

Question

I'm using this to get the newest item. How can I get this to be null safe and sort with null dates last (oldest). createDt is a joda LocalDate object.

Optional<Item> latestItem = items.stream()                              .sorted((e1, e2) -> e2.getCreateDt().compareTo(e1.getCreateDt()))                              .findFirst(); 

Answer 1

If it's the Items that may be null, use @rgettman's solution.

If it's the LocalDates that may be null, use this:

items.stream()      .sorted(Comparator.comparing(Item::getCreateDt, Comparator.nullsLast(Comparator.reverseOrder()))); 

In either case, note that sorted().findFirst() is likely to be inefficient as most standard implementations sort the entire stream first. You should use Stream.min instead.

Answer 2

You can turn your own null-unsafe Comparator into an null-safe one by wrapping it Comparator.nullsLast. (There is a Comparator.nullsFirst also.)

Returns a null-friendly comparator that considers null to be greater than non-null. When both are null, they are considered equal. If both are non-null, the specified Comparator is used to determine the order.

.sorted(Comparator.nullsLast(      (e1, e2) -> e2.getCreateDt().compareTo(e1.getCreateDt()))) .findFirst();