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

How about the following pseudo code (w/o recursion)

// Create the initial result filled with the first set of numbers
List result = new List()
For each number in the first set
   result.add(new List(number))

// Iterate over the following sets to permutate over
For each remaining set S
   List newResult = new List()
   For each list L in result
     For each number N in S
       newResult.add(copy of L with N added)
   result = newResult