import java.util.ArrayList;
import java.util.List;

public class Solution {

    public List<List<Object>> cartesianProduct(Object[] a, Object[] b) {
        List<List<Object>> result = new ArrayList<>();

        
        if (a == null || b == null || a.length == 0 || b.length == 0) {
            return result;
        }

        for (Object itemA : a) {
            for (Object itemB : b) {
                List<Object> pair = new ArrayList<>(2);
                pair.add(itemA);
                pair.add(itemB);
                result.add(pair);
            }
        }

        return result;
    }
}