ITI 1120 Winter 2013 - Assignment 5

Available:  March 31
Due:  Wednesday, Apr 10, 22:00.

Instructions

This assignment is to be done in TEAMS OF TWO PEOPLE.  The assignment should be submitted only once by a member of your team, but please ensure that the identification material contains the information for both team members. 

For this assignment, classes should be in files with names that match the name of the class. Make sure the method names are exactly the ones specified, because the marking will be done with JUnit tests.

Marking scheme:

• Regulations and standards: 10 marks
• Question 1: 20 marks
• Question 2: 15 marks
• Question 3: 25 marks
• Question 4: 30 marks

Question 1): (20 marks)

In this question, you will create a class User that will store information about the users of an online service similar to EBay. The users can sell items (register items for sales), other users can bid for these items, and each item will be sold to the user that offers the highest price during the bidding process.

See the UML diagram for the class User (UML diagrams specify the attributes of a class and their types and the method headers that you should use in your Java code) in the file A5_uml.pdf

Attributes:

User objects will store the following information for each user:

• The name of the user
• The login of the user
• A password used by the user

Constructors:

As a User object is created, a value should be supplied for the name, the login, and the initial password.

Here is the constructor header:

• public User( String userName, String userLogin, String initialPassword )

Accessors and Modifiers:

Public accessor methods should be available for the name and login. A public modifier method should be available for the name. Here are the method headers:

• public String getName( )
• public String getLogin( )
• public void setName ( String newName )

Additional methods

There should also be a method that compares a password entered by the user with the stored password. This method should return true if the user entered the correct password, and false otherwise.

There should be a method to change the user’s password. A password change is only permitted if the old password can be given, so the two parameters are the entered password and a new password. The entered password is compared with the password stored inside the object. If the password is correct, then the new password replaces the previous password inside the object. To indicate that the operation was successful, the method should return true. If the entered password was incorrect, the password stored in the object should remain unchanged and the method should return false.

You should be very careful that a user object never gives out the stored password.

Testing

Test your User class using the JUnit class UserTest.java. You can do more testing for yourself, but make sure that the tests from UserTest.java (without modification) run properly.

Question 2 (15 marks)

In this question, you will create a class Item that will store information about items that can be purchased.

See the UML diagram for the class Item in the file A5_uml.pdf

Individual Item objects will store the following information for each item:

• The name of the item (a description)
• An indication whether the item is new or used (newItem is set to true if the item is new, and to false if the item is used).

There should also be accessor and modifier methods these two values (see the UML diagram for the method headers).

Testing

Test your Item class using the JUnit class ItemTest.java. You should do more testing for yourself, but make sure that the tests from ItemTest.java (without modification) run properly.

Question 3 (25 marks)

In this question, you will create a class Transaction that will store information about a specific online event that happens on your EBay-type server. When a user wants to sell or buy an item, this class will represent the association between a User object and an Item object that is involved in the transaction.

See the UML diagram for the class Transaction in the file A5_uml.pdf

Attributes:

There are some values that apply to all Transaction objects:

• Type code numbers: 0 for SELL, 1 for BID, and 2 for FINAL_SALE. These are constant values that denote, respectively, a selling transaction, a bid, and a purchase that happens for the user that wins the bidding. These integers need to be assignment to the variable type.
• A number that represents the next confirmation number available when a new transaction is registered into the server.

Individual Transaction objects will store the following information for each transaction:

• A confirmation number that uniquely identifies the transaction and serves as prove that the server registered the actions of the User (the static variable nextConfirmation will provide the next available number to be used as confirmation number)
• A reference to the User that registered the Transaction
• A reference to the Item object involved (the item can be proposed for selling, proposed for buying – bid for, or actually purchased) as part of this transaction.
• The type of the transaction (one of the three codes SELL, BID, or FINAL_SALE).
• The status of the transaction (active or not). A SELL transaction becomes inactive after the item is sold (purchased). A BID transaction becomes inactive after the item is sold (regardless of whether the bid was successful or not). FINAL_SALE transactions should be set as active.
• The price involved in the transaction (this is the selling price if it is a SELL transaction, the bidding price if it is a BID transaction, and the price of purchase if it is a transaction of type FINAL_SALE).

Constructor:

The constructor header is as follows:

• public Transaction(User user, Item item, double price, int type)

Each time a new Transaction object is created, the next highest confirmation number not previously used should be stored. The confirmation number for the very first Transaction object created should be 100.

Also at the time of creation, the User reference, the references to the Item object, the price, and the type of the transaction should be stored.

Accessors and Modifiers:

There should be public accessor methods for the confirmation number of each transaction, for its type, for its status (active or not), for the User associated with the transaction, for the Item, and for the price. There should be public modifier methods to allow changing the price and the status of a transaction.

Testing

Test your Transaction class using the JUnit class TransactionTest.java. You should do more testing for yourself, but make sure that the tests from TransactionTest.java (without modification) run properly.

Question 4 (30 marks)

In this question, you will create a class MyEBServer that will store the collection of transactions, execute the biddings and the final purchases, and print some summary statements.

See the UML diagram for the class MyEBServer the file A5_uml.pdf

Because we do not want to allow more than one collection of transactions, the class MyEBServer will use (private) static array variables to store references to different kinds of Transaction objects. This also means that no MyEBServer objects are created. With no MyEBServer objects, all variables and methods must be static.

The class stores pointers to three arrays of transactions: an array of proposed selling transactions named registeredSales, an array of bidding transactions named registeredBids, and an array of purchases (finalized sales). The maximum number of entries in any of these three arrays is given as parameter in the initialize method (the same size for all three arrays). There is also an integer variable for each of the three arrays, to store the actual number of transactions of each kind that took place.

The method initialize(...) should create capacity for a specified number of Transaction objects to be stored in each of the three arrays in the MyEBServer class. However, no Transaction objects are added at this time.

The method addItemToSell(...) will attempt to add a Transaction object of type SELL to the array registeredSales. It will call the constructor of the class Transaction to create the new transaction for the specified user, item, price, and type. If there is space to hold another Transaction object, the object should be added, and the number of registered sales should be incremented. If the array has no more room to store additional objects, an error message should be printed.

• Sample error message: "The catalogue of registered items to sell is full."

The method addBid(...) will attempt to add a Transaction object of type BID to the array registeredBids. It will call the constructor of the class Transaction to create the new transaction for the specified user, item, price, and type. If there is space to hold another Transaction object, the object should be added and the number of registered bids should be incremented. If the array has no more room to store additional objects, an error message should be printed.

• Sample error message: "The bidding register is full."

The method displayBidsForItem (...) displays all the bids for a given item. It is useful when a new bidder wants to see what were the current bids, to be able to bid a higher price.

The method getBidsForItem(Item item) returns an array with all the BID transactions for the item. The array should be of the right size (the number of bids, not longer). The method returns an empty array if there are no bids for the item.

The method getMaxBidForItem(Item item) returns the Transaction that corresponds to the highest bid. The method return null if there are no bids for the item.

The method executePurchases( ) goes through all the selling transactions in the array registeredSales. For each active selling transaction (only the active ones), it goes through the bids from the array registeredBids (only the active ones). Then it chooses the highest bid and finalizes the purchase by adding a transaction of type FINAL_SALE to the array of purchases (for the same item and user as in the BID transaction, and status set to active). The status of the respective selling and bidding transactions has to be made inactive. An item should not be sold to a bidder that offers less than the asking price. In this case the item is not sold, it remains in the register of sales. Similarly, if there are no bids for an item, it will not be sold (not until somebody bids for it).

The method displayPurchases( ) displays all the purchases (finalized sales) that happened in the server. It displays only the prices offered, separated by one space.

Testing

Test your MyEBServer class using the class A5Q4.java that should produce exactly the output A5Q4.txt. This class contains the main method with a sample run of the MyEBServer. You can run more tests for yourself, but make sure the class A5Q4.java (non-modified) produces the required output.