How can I make Cartesian product with Java 8 streams?

Question

I have the following collection type:

Map> map;

I would like to create unique combinations of each o

Answer 1

In loop create combined list

List cartesianProduct(List> wordLists) {

 List cp = wordLists.get(0);

 for (int i = 1; i < wordLists.size(); i++) 
 {      
     List secondList = wordLists.get(i);
     List combinedList = cp.stream().flatMap(s1 -> secondList.stream().map(s2 -> s1 + s2))
                    .collect(Collectors.toList());
        cp = combinedList;

    }
        return cp;
}