Consider the Show interface and the two implementing classes Movie and Concert. Create a class SponsoredConcert that is a subtype of Concert with two additional pieces of data: a sponsor name (String) and a sponsor time (int) that represents the number of minutes the sponsor is allocated to advertise as part of the show. A call to description() on an instance of SponsoredConcert should include the title and performer of the concert, along with the name of the sponsor. A call to time() on an instance of SponsoredConcert should return the time of the concert plus the time allocated to the sponsor.
Change the code of Concert so that the field aPerformer is private. What are possible solutions for accessing this information?
Create an abstract class AbstractShow that groups all the fields that Concert and Movie have in common. Refactor your class hierarchy to use this abstract class with as tight encapsulation as possible.
Draw a class diagram of the refactored design completed in Exercise 3, then extend the diagram to show how CompositeShow (a composite) and IntroducedShow (a decorator) would integrate the design.
We want to ensure that calling method description() on an instance of any type of Show returns a string with the following format:
$TITLE$: [...] ($TIME$ minutes)
where $TITLE is a placeholder for the title of the show, and $TIME is a placeholder for the total running time of the show. Implement this functionality by applying the Template Method design pattern.
Draw a UML sequence diagram that model the sequence of calls that results from an invocation of method description on an instance of SponsoredConcert. To clarify which implementation of a method is used, name the call using the convention Class#Method, so that for example a call to method time() of class SponsoredConcert would be labeled as SponsoredConcert#time().
Consider the class AbstractShow created as part of Exercise 3. Add a method setTitle(String) in AbstractShow to set the title of the show. Because the title of a movie does not change after the movie is released, override setTitle to throw an UnsupportedOperationException. Similarly, implement a method setTime in AbstractShow with an input precondition of > 0, and override this method in Movie to have the precondition > 10. Does class Movie respect the Liskov Substitution Principle? Support your answer with a piece of demonstration client code.
Assume class AbstractShow provides a method setTime(int minutes). Add an additional method setTime(int hours, int minutes) that sets the time of the show as hours * 60 + minutes. Is this a case of overloading or overriding? Now remove the implementation of setTime(int hours, int minutes) and add it to class Movie instead. Is this a case of overloading or overriding? Does it make a difference whether we place this method in AbstractShow or Movie?
We wish to add a recommendation feature to our Show type hierarchy, where Show instances can hold a reference to a "recommended" show (if a person likes a given show). For this purpose, add a field Show aRecommended to class AbstractShow, together with public methods Show setRecommended(Show) and Show getRecommended(). For movies, we wish to constrain recommendations to movies only, so that movies can only hold recommendations to other movies. Override methods setRecommended and getRecommended in class Movie to only take Movie as parameter and return Movie, respectively. Does this design respect the Liskov Substitution Principle? Support your answer with a piece of demonstration client code.
Make the Show class hierarchy Cloneable so that it is possible to clone instances of Concert, Movie, or SponsoredConcert.
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