辅导SYSC2004 Flashcards辅导Java编程、Java设计辅导

使用Java代写游戏Flashcards.

Objectives

• To practice writing and subclassing abstract classes
• To practice the use of HashMap as a database
• To practice reading and writing files

Rules of the Game

Flashcards are used to help some memorize a set of facts. They offer students repetitive practice in a particular set of facts. Each flashcard has a question on its front (Example: 4 + 8 = ?) and the correct answer on its back (Example: 12). The first flashcard is revealed and the student attempts to answer correctly. If the answer is correct, this particular flashcard is set aside (so that the student is not asked something that they already know again) and the student gains a point in their total score. Instead, if the answer is incorrect, this flashcard is re-inserted, randomly, back into the deck of flashcards, and no point is earned. Play continues until all flashcards are correctly answered, or until the student tires and quits.

Flashcards are used in many subject matters - to practice math facts (e.g. addition and multiplication tables), to practice language vocabulary (e.g. from French to English, or vice versa), to master all the bones in the body in anatomy class. The software that we write should be extensible to allow the implementation of this variety of flashcards. An abstract class hierarchy will be used to demonstrate one possible design approach (and to give you practice in using abstract classes).

Explanation of the UML class diagram

1. AbstractFlashCards is a parent class incorporating all that is common between different varieties of flashcards, whether they are used for math, language or anatomy. The class is abstract even though all of its methods are concrete. The rationale is that even though it is known how to implement the methods, we don’t know fully how to create the deck (i.e. we need more constructors) so therefore we don’t want clients to instantiate this class.
   • Look at its concrete subclass called LanguageFlashCards. Its constructor has an argument called filename, suggesting that these cards are to be read in from a file.
     • The file (EFdictionary.csv) to be read is posted as part of the assignment. Look at its contents. It is a simple csv file. Writing this class will provide you with some more practice reading files.
   • Look at its other concrete subclass called MultiplicationFlashCards. Its constructor(s) has(have) an argument called multiplier(s), suggesting that these cards will not be read in from a file, but will be automatically generated for a given multiplier (Example: If the single multiplier is 10, twelve cards will be automatically generated for 1x10, 2x10 12x10. If instead an array of multipliers is provided (say, [2,5,7]), thirty-six cards will be generated: 12 for 2, then 12 for 5, then 12 for 7
     • In the UML class diagram, take note that this subclass has no instance variables. You will simply write programming logic to automatically generate the described sequences of cards.
2. The instance variables of AbstractFlashCards
   • flashcards is a hashmap (i.e. a dictionary) with the question on the front of the flashcard as the key and the answer on the back of the flashcard as the value. It contains the original complete deck of flashcards.
   • unansweredCards is a randomly-ordered copy of all questions (because you can look up the answer later when the question is used.). A separate randomized copy is needed because the flashcards stored in the hashmap have a specific ordering; simply iterating over the hashmap will lead to a very boring game. Originally, it will contain the complete deck in random order. The first element (index = 0) is the next question to be presented. If the student answers it correctly, the question is removed from this list; if the student answers it incorrectly, the question is reinserted at a random location within this list. The game is over when this list is empty.
   • score is a simple integer number incremented whenever a correct answer is given.
   • scanner is necessary for the class to read in answers from the console.
3. The methods of AbstractFlashCards are all concrete
   • The constructor shall initialize all instance variables. These variables are initialized even though you can’t actually fill the decks with concrete cards.
   • addCard() is a protected method. Use of protected is a signal that this method is intended for use by any subclass. Its role is to put a lt;question,answergt; entry into the flashcards hashmap. (Sample Exam Question: Why can’t the subclasses do it directly? Why is this protected method needed?)
   • reset() does not alter the existing flashcards; instead it is used to re-shuffle the entire deck, meaning that it clears out the unansweredCards and creates a new random ordering of the questions.
     • This is a programming challenge for you to conquer, to push the limits of your problem-solving skills. If you cannot figure it out, post a question on this Assignment’s CULearn discussion forum.
     • Handy syntax: To convert any Java Collection (e.g. aCollectionlt;Stringgt;) into an equivalent array.
     • Handy syntax: To construct an ArrayList that is a copy of an existing array, there is the one-argument constructor (instead of the usual default constructor which creates an empty list)
   • hasNext() returns true if there are any remaining unansweredCards.
   • nextCard() is the heart of the game. The method prints the next unansweredCards and reads in the user’s answer. If the answer is correct, the card is removed from the list of unansweredCards, the user’s score is advanced, and the method returns true. If the answer is incorrect, the card is re-inserted - at a random place - back into the list of unansweredCards, and the method also returns true. The method only returns false if there are no remaining unansweredCards.

Writing the Code

Because of the abstract class (which you cannot instantiate to test), you will have to write more than one class at a time. When presented with a large task, it is always good to work incrementally. Don’t write the whole class; write parts of the class and then test them, before proceeding to write more.

The two games are very similar. Complete one game (e.g. the LanguageFlashCardsApplication) so that you understand the game fully. Then write the other one, because you will only have to write code for the differences.

Tip: In this assignment’s project, you will have two classes with a main() method. Instead of using the RUN menu (which launches the main() method of the alphabetically-first class in the project), you will have to identify WHICH main() to run.

• On the right-side PROJECT window, right-click on the desired xxxApplication.java and select RUN.

On the next two pages are the expected console dialogues that you will have to replicate with your programs, one for LanguageFlashCardsApplication and one for MultiplicationFlashCardsApplication. The two are very similar, except for the content of the cards and for the initial prompts about how to create the cards.

LanguageFlashCardApplication : Sample Console Input/Output that you are to replicate

• Blue are the console output to be printed in main() to direct the sequence of the game.
• Black are the console inputs entered by the user (i.e. you)
• Red are console outputs used for supporting testing, to be printed by the AbstractFlashCard::nextCard() method. It is used to prove that you are presenting the cards in random order, and that after a wrong answer, you are inserting the card back into the pile at a random location.

MultiplicationFlashCardApplication : Sample Console Input/Output that you are to replicate

• Blue are the console output to be printed by main(), to direct the sequence of the game.
• Black are the console inputs entered by the user (i.e. you)
• Red are console outputs used for supporting testing, to be printed by the AbstractFlashCard::nextCard() method. It is used to prove that you are presenting the cards in random order, and that after a wrong answer, you are inserting the card back into the pile at a random location.

Marking Scheme

Assignments will not be accepted if standard indentation is not used. A mark of zero will be earned.

Instruction to TAs: Make sure your write your initials on each assignment that you mark, so that the student knows who to contact for concerns about their mark.

Instructions to Students: Afterwards, if you have a question about the marking of your assignment

1. On the course webpage, study the schedule for the TAs and see when your TA is on duty in the lab. If you do not have a class/lab conflict with that time, visit the TA during their lab period.
2. Alternatively, email the TA that marked your assignment. Pose your question if it is simple; if not, request a meeting. If you do not receive a reply from the TA within 2 working days, re-send your email and now ‘cc your instructor so that s/he can follow up.