public class Box<T, S> { private T item1; private S item2; // Constructors, getters, and setters } Box<String, Integer> wordAndIntegerBox = new Box<>("Hello", 5); public class Util { public static <T, S> boolean areNumbers(T item1, S item2) { return item1 instanceof Number && item2 instanceof Number; } } boolean areNums = Util.areNumbers("Hello", 34); // false