Sets.cartesianProduct gives undocumented IllegalArgumentException due to its size

[Meijuh]

The following piece of code throws an undocumented IllegalArgumentException:

final Set<String> products = Sets.newHashSet("coffee", "tea");
final List<Set<String>> productOf = Collections.nCopies(31, products);    
assert Sets.cartesianProduct(productOf).size() == Integer.MAX_VALUE;

The fact that Sets::cartesianProduct will throw an IllegalArgumentException when there would be more than 2^31-1 elements in the resulting set is not documented as far as I can see.

I would like to see one of two solutions:

1. Document why this Exception is thrown (there may be an implementation detail that prevents even defining such large sets).
2. Fix it, because java.util.Set::size() specifies that if the size would be more than Integer.MAX_VALUE it would simply be Integer.MAX_VALUE.

I like to see this fixed (solution 2), because now I can't even define such a Cartesian product. Iterating over so many elements is of course a different issue, but I have a piece of code that may very quickly find an element in the product, because I know it is in there and due to some ordering on element.

[hembhagat99]

@Meijuh @kluever I think we should fix this(solution 2). I will have a look at it.