Null safe date comparator for sorting in Java 8 Stream
JavaJava 8Java StreamJava Problem Overview
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();
Java Solutions
Solution 1 - Java
If it's the Item
s that may be null, use @rgettman's solution.
If it's the LocalDate
s 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.
Solution 2 - Java
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();