How to create cartesian product over arbitrary groups of numbers in Java?

Question

Let\'s say I have 2 groups of numbers:

{1, 2, 3},
{4, 5}

I\'d like to create an algorithm (in Java) that outputs the following 6 combinations:<

Answer 1

If you can use libraries, Guava's Sets.cartesianProduct(List>) does exactly what you're looking for. (Disclosure: I contribute to Guava.)