Description

Contributor List:
Design: Yitong WANG, Yida TAO
JUnit: Yitong WANG, Dingyuan XUE
Document: Yida TAO
Solution & Test: Siyi WANG, Sicen LIU
Question 1. BigBinary [Medium, 40 + 15 Points]
Contributors: Yitong WANG, Siyi WANG
In the course CS202: Computer Organization, it is introduced that computers store data in the binary form.
YeeTone is a student of CS major but not good at solving binary number arithmetic problems, so he asks you for help. Fortunately, he is very familiar with Java programming. If you can help YeeTone solve problems by designing a class in Java, he will be very happy!
Please design a Java class named BigBinary to give a hand to YeeTone. Notice that in order to let YeeTone really trust you have the ability to help him solve the problems, YeeTone does not want you to use some classes in the libraries of Java such as java.math.BigInteger in this problem.
Constructor

Design a constructor with two parameters:
An int array bits consisting of 0s and 1s, meaning the corresponding bit values. 0 <= bits.length <= 1,5000. Notice that in order to ensure the data security, you should not copy the reference but the values of bits.
A boolean positive, indicating whether the sign of BigBinary object is positive.
In the following examples, ^ means power in math instead of XOR. For instance, 3^5 = 3*3*3*3*3=243.
Example 1

The bigBinary can express the binary number -10110, whose decimal number is -(2^4 + 2^2 + 2^1) = -22.
Example 2

The bigBinary can express the binary number 0, whose decimal number is 0.
Example 3

The bigBinary can express the binary number 100011, whose decimal number is 2^5 + 2^1 + 2^0 = 35.
Methods public String toString();
This method can return the BigBinary in a binary format. Notice that if there exists at least one 1 in the binary form, then the leading 0s should not be output; otherwise return “0”. For example, if the BigBinary is -0011011, the toString() method should return “-11011”; if the BigBinary is -00000, the toString() method should return “0”.
Sample code:

Sample Output:

After executing the method, the original BigBinary and the return value should be the sum of this BigBinary and the parameter bigbinary(i.e. this BigBinary + bigBinary).
public BigBinary minus(BigBinary bigbinary);
After executing the method, the original BigBinary and the return value should be the difference between this BigBinary and the parameter bigbinary(i.e. this BigBinary – bigBinary).
public BigBinary multiply(BigBinary bigbinary);
(Bonus) After executing the method, the original BigBinary and the return value should be the product of this BigBinary and the parameter bigbinary(i.e. this BigBinary * bigBinary).
public static BigBinary add(BigBinary b1, BigBinary b2);
After executing the method, the return value should be the sum of BigBinary b1 and BigBinary b2(i.e. b1 + b2).
BigBinary b1 and b2 should not be changed.
public static BigBinary minus(BigBinary b1, BigBinary b2);
After executing the method, the return value should be the difference between BigBinary b1 and BigBinary b2(i.e. b1 – b2). BigBinary b1 and b2 should not be changed.
public static BigBinary multiply(BigBinary b1, BigBinary b2);
(Bonus) After executing the method, the return value should be the product of BigBinary b1 and BigBinary b2(i.e. b1 * b2). BigBinary b1 and b2 should not be changed.
Question 2. Online Shopping [Medium, 60 + 5 Points]
Contributors: Yida TAO, Sicen LIU, Dingyuan XUE
The advance in E-commerce has made online-shopping a pervasive and convenient daily experience. Customers could browse different online stores, each of which provides a list of products for customers to buy.
In this question, you’ll build three classes, Product, Store, and Customer, to implement the online shopping process. See below for detailed requirements. Note that to implement the required functionality, you are free to add variables and methods that are not mentioned in this document; however, please DO NOT change the definitions of the existing variables and methods that we have specified in this document. 2.1 Product
Attributes

Constructor

The constructor of the Product class.
The id of the first product is 1. The given price is always valid.
Methods

public boolean setRating(int rating);
Set rating to the product. The rating would be added to this product’s rating list ratings.
A rating should be within the range [1,5]; in other words, there are only 5 possible values for rating.
If rating is not in this range, do not add it into rating and return false.
public float getAvgRating();
Return the average rating of this product, which is computed as the average of all the ratings it has received so far.
public String toString();
Return a string description of this product, in the format of Product ID id, name, RMB price, Rating average-rating, e.g., Product ID 12345, Laptop, RMB 10000.00, Rating 4.5.
Round price to 2 decimal places and rating to 1 decimal place.
2.2 Store
Attributes

Constructors

There are two constructors of the Store class. One for constructing a new store, with income = 0 and nothing in the productList. The other constructs an existing store with given income and productList.
The id of the first store is 1. The given income and productListare always valid.
Methods

public boolean hasProduct(Product product);
A method to determine whether this store has the given product . Return true if the product is in the productList of the store; otherwise, return false.
public boolean addProduct(Product product);
Add product to the productList; return a boolean indicating whether the operation succeeds.
Suppose each product, which is uniquely identified by its id, could only appear once in the productList of a particular store. That is, the same product will not appear in the productList of multiple stores (this kind of invalid case will not happen); and in the same productList, a product appears not more than once.
If a product already exists in productList, return false and productList remains the same; otherwise, add product to productList and return true.
public boolean removeProduct(Product product);
Remove product from productList; return a boolean indicating whether the operation succeeds.
If product exists in productList, remove it from productList and return true; otherwise, return false and productList remains the same.
public ArrayList<Product> getProductList(); Return productList.
public void transact(Product product, int method);
This is an interface method for stores to handle customers’ purchases or refunds. Suppose that all the arguments are valid here.
method = 0 means purchasing the product from this store. The product should be removed from the productList and the income of this store should increase by an amount equal to the price of the product.
(Bonus) method = 1 means refunding the product to the store. The productList and income of the store should also be updated accordingly (suppose that the store adds this product back to its productList and could re-sell this product).
2.3 Customer
Attributes

Constructor

The constructor of the Customer class.
The id of the first customer is 1. The given wallet is always valid.
Methods

public boolean rateProduct(Product product, int rating); A customer can rate a product using this method.
For invalid rating, return false; otherwise return true.
public void updateWallet(float amount);
Update the wallet of this customer. The amount could be positive (gaining money) or negative (consuming money). Assume that arguments are always valid.
public boolean purchaseProduct(Store store, Product product); Purchase product from store.
Return true if the store has this product and the customer has enough money in the wallet to purchase this product; return false otherwise. Note that the shoppingCart of this customer as well as his/her wallet should be updated accordingly.
public void viewShoppingCart(SortBy sortMethod);
Display the purchased products in the shoppingCart of this customer. The order of displaying is specified by sortMethod. Below we provide an Enum SortBy, which says that sorting could be performed by the PurchaseTime, Rating, or the Price of products.

Suppose a customer Alice has purchased a few products from different stores.

Then, calling

will display (see Product.toString() for the format)

Calling

will display

public boolean refundProduct(Product product);
(Bonus): Return the product to the store where it was sold and get the money back. Return true if this customer has indeed purchased this product before and false otherwise. Note that the shoppingCart and wallet of this customer should be updated accordingly. In addition, the corresponding store should enable the refund process to update the productList and income.
Tips
We prepared a bilingual helping document(双语帮助文档) for this assignment. Please refer to this document first if you have any trouble solving the problems.
We prepared sample test cases for Q1 and Q2, along with a documentation explaining how you could use JUnit to run these tests locally. Although OJ uses a different set of test cases, the sample tests are useful for testing and debugging purposes.
Submission
You need to submit BigBinary.java for question 1, Product.java, Store.java, Customer.java and SortBy.java for question 2. Notice that you should NOT contain any Chinese character in the submitted java files.