How to get percentage of object in Java Streams

I have stream of integers and I try to find percentage of 1’s over all. I cannot find the solution.

connections
        .flatMap(co -> co.stops().stream())
        .map(ts -> ts.kind() == kind ? 1.0 : 0.0)

I don’t want to share class types and make things complicated. I just want to calculate percentage.

>Solution :

Rather than map, use mapToInt to get an IntStream, and then average() will get you the percentage you want:

.mapToInt(ts -> ts.kind() == kind ? 1 : 0).average()

This gives you an OptionalDouble, which will be empty if the stream is empty.