Find the maximum product of five consecutive integers.

maxProductOfFiveConsecutiveInts.java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Optional;
import java.util.stream.Stream;

import static java.lang.Integer.parseInt;
import static java.util.Comparator.naturalOrder;

public class Test {

    static final String nums = "37900490610897696126265185408732594047834333441947018503938074170641817003483791166860080189669498677558722248271653685006165703758078020538662914584106964490601037178417735301109842904952970798120105470168021976855478449620066905768943533366888238302291333721473491149055521813412305168905832929411783011983450277211542535458190375258738804563705619552777408744641552952789449531990152618001564228057277177446096431068469989305514445184509262635998279063901081322647763278370447051079759349248247518";

    public static void main(String[] args) {
        Stream<Stream<Integer>> partitioned = partition(nums, 5)
            .stream()
            .map((str) -> Arrays.asList(
                str.charAt(0),
                str.charAt(1),
                str.charAt(2),
                str.charAt(3),
                str.charAt(4)
            ))
            .map((chars) ->
                chars
                    .stream()
                    .map((chr) -> parseInt(String.valueOf(chr)))
            );
        Integer max = partitioned
            .map((stream) -> stream.reduce((a, b) -> a * b).get())
            .max(naturalOrder())
            .get();
        System.out.println(max); // Will print 34992
    }

    static Collection<String> partition(String str, int partitionSize) {
        Collection<String> partitions = new ArrayList<>();
        for (int i = 0; i < str.length();) {
            partitions.add(str.substring(i, i + partitionSize));
            i = i + partitionSize;
        }
        return partitions;
    }
}

In Haskell: https://gist.github.com/laurilehmijoki/6829074
In Clojure: https://gist.github.com/laurilehmijoki/6829426