Sum distances between points in list using Java8 Streams

Question

I have a list of points (x,y) and I want to sum the distances between them. In old Java I would do it like this:

List<Point> points = ...
long sum = 0;
for (int i = 0; i < points.size() - 1; i++) {
    sum += PointUtil.distance(points.get(i), points.get(i + 1));
}
return sum;

Now the question is: can I do the same code using points.stream(). ...?

Answer 1

Yes. You can use IntStream, in order to have indexing:

long sum = IntStream.range(0, points.size() - 1)
                    .mapToLong(i -> PointUtil.distance(points.get(i), points.get(i + 1)))
                    .sum();

Answer 2

Here's the first thing I could think of:

sum = IntStream.range(0,points.size()-1)
               .mapToLong(i -> PointUtil.distance(points.get(i), points.get(i + 1)))
               .sum();