An apologia of lazy evaluation(epicandmonicisnotiso.blogspot.com)

  g (f input)

    That might seem the case from afar, but once you start writing Haskell and
    start experimenting these space leaks, you will notice that:

    1. 90% of the space leaks you write end up adding a tiny amount of memory
    usage to your functions, mostly unnoticeable. Think thunks like (1 + 2) that
    are subjected to demand analysis under optimization.

    2. 1-2% of them are serious enough to require profiling your code with
    cost-centres.

    import java.util.OptionalInt;
    import static java.util.stream.IntStream.iterate;
    public class Main {
        public static void main(String[] args) {
            System.out.println(fun().getAsInt());
        }
        static OptionalInt fun() {
            return iterate(0, a -> a + 1)
                    .flatMap(b ->
                            iterate(b, c -> c + 1)
                                    .flatMap(d -> iterate(d, e -> e + 1)))
                   .findFirst();
        }
    }

    Exception in thread "main" java.lang.OutOfMemoryError: Java heap space