Java streams findAny() encounters null pointer exception after filter() operation filters out everything

Question

I am having trouble figuring why findAny() throws a null pointer exception after filter() operation on a stream. In this particular test case, the filt

Answer 1

No, it's not the behavior, when the stream doesn't contain any elements. In which case it instead returns an Optional.empty().

Also, the NPE is the cause of a null value in the stream, as stated in the javadocs:

Returns:
an Optional describing some element of this stream, or an empty Optional if the stream is empty

Throws:
NullPointerException - if the element selected is null

Answer 2

Your confusion comes from the fact that you filter first - and you would expect the filter method to be somewhere in the stack trace; but notice that intermediate operations do nothing per-se, they are executed lazily and only kick in when a terminal operation is present (such as findAny in your case). It's actually there in the stack trace (the filter method), but it looks like this: Example.Main.lambda$main$0(Main.java:41).

If you want to filter null values, first do:

.filter(Objects::nonNull)
.filter(n -> n.textValue().equals("AES256"))
.findAny()

Answer 3

The best way to avoid NPE is:

Optional<JsonNode> encryption = sseEncryptionList.stream()
              .filter(Objects::nonNull)
              .filter(n -> "AES256".equals(n.textValue()))
              .findAny();

"AES256".equals(n.textValue())) will not throw NPE if n.textValue() is null