all possible combination of n sets

Question

I have n Sets. each Set has different number of elements. I would like to write an algorithm which give me all possible combinations from the sets. for example: Lets say we have

Answer 1

Great solution by krilid, I modified it a bit to return a list of all combinations.

@Test
public void testMap() throws Exception {
    char[] one = new char[]{'a', 'b', 'c'};
    char[] two = new char[]{'d', 'e', 'f'};
    char[] three = new char[]{'g', 'h', 'i', 'j'};
    char[][] sets = new char[][]{one, two, three};
    List> collector = new ArrayList<>();
    ArrayList combo = new ArrayList<>();
    combinations(collector, sets, 0, combo);
    System.out.println(collector);
}

private void combinations(List> collector, char[][] sets, int n, ArrayList combo) {
    if (n == sets.length) {
        collector.add(new ArrayList<>(combo));
        return;
    }
    for (char c : sets[n]) {
        combo.add(c);
        combinations(collector, sets, n + 1, combo);
        combo.remove(combo.size() - 1);
    }
}