The following lines declare a PartyWithHearable subclass of the previously created Party<T> class that takes advantage of generics to work with two constrained types. The type constraints declaration is included within angle brackets (<>). In this case, we have two generic type parameters: T and U. The generic type parameter named T must implement both the Sociable and Comparable<Sociable> interfaces, as it happened in the Party<T> superclass. The generic type parameter named U must implement the Hearable interface. Notice that the extends keyword that follows the type parameter allows us to add the constraints to the generic type parameters and the same keyword after the angle brackets specifies that the class inherits from the Party<T> superclass. This way, the class specifies constraints for both the T and U generic type parameters, and inherits from Party<T>.The code file for the sample...