Cartesian product of arbitrary sets in Java

Question

Do you know some neat Java libaries that allow you to make cartesian product of two (or more) sets?

For example: I have three sets. One with objects of class Person

Answer 1

The method below creates the cartesian product of a list of list of strings:

protected <T> List<List<T>> cartesianProduct(List<List<T>> lists) {
    List<List<T>> resultLists = new ArrayList<List<T>>();
    if (lists.size() == 0) {
        resultLists.add(new ArrayList<T>());
        return resultLists;
    } else {
        List<T> firstList = lists.get(0);
        List<List<T>> remainingLists = cartesianProduct(lists.subList(1, lists.size()));
        for (T condition : firstList) {
            for (List<T> remainingList : remainingLists) {
                ArrayList<T> resultList = new ArrayList<T>();
                resultList.add(condition);
                resultList.addAll(remainingList);
                resultLists.add(resultList);
            }
        }
    }
    return resultLists;
}

Example:

System.out.println(cartesianProduct(Arrays.asList(Arrays.asList("Apple", "Banana"), Arrays.asList("Red", "Green", "Blue"))));

would yield this:

[[Apple, Red], [Apple, Green], [Apple, Blue], [Banana, Red], [Banana, Green], [Banana, Blue]]

Answer 2

how about using odl.com.google.common18.collect.Sets and calling Sets.cartesianProduct() method

Answer 3

This is a pretty old question, but why not use Guava's cartesianProduct?