Get index of element that matches a predicate

Question

I know how to find the first element of a list by predicate: Find first element by predicate

Is there an easy way to get the index of that element?

This question is NOT a duplicate to https://stackoverflow.com/questions/23696317/java-8-find-first-element-by-predicate. Although answers to that question can be used to construct an answer to this one, there could also be answers which don't require iterating the stream. — Lii, Feb 11 '22 at 13:23

score 18 · Accepted Answer · answered Apr 25 '17 at 08:46

18

If I understood correctly, that's the classic case where you need IntStream; but that would only apply for a List obviously.

IntStream.range(0, yourList.size())
   .filter(i -> yourList.get(i)... your filter condition)
   .collect(Collectors.toList());

answered Apr 25 '17 at 08:46

Eugene

8

If you really only want the first index, use `findFirst()` instead of `collect(...)`. This will only execute the filter until you find the first match. – Malte Hartwig Apr 25 '17 at 12:01

1 Answers1