public class SimplePairUsage {
  public static void main(String args[]) {
    Pair<String, Integer> p1 = new SimplePair<String, Integer>("Even", 8);
    Pair<String, String>  p2 = new SimplePair<String, String>("hello", "world");
    SimplePair<String, Box<Integer>> p3 = new SimplePair<>("primes", new Box<Integer>());
    // the following is not allowed
    Pair<String, Integer> p4 = new SimplePair<>("hello", "world");
  }
}