Overview

We will see the power of Object-Oriented Programming (OOP) when we want to create a program that behaves similar to what we have done before (code reuse). This lab will not be limited to just 3 specialty cheeses but any amount set by the user. Luckily, this does not change anything for the Cheese class, and we just have to create a shop that contains an array of items to sell, which we will call ShopArr.

Before you get started, read chapters 7.10, 7.11, and 7.12. Answer the Assessment questions as you encounter them in the next section. The prompts for answering assessment questions are placed immediately following the material to which the listed questions relate.

Getting Started

After following the import instructions in the assignment page, you should have a Java project in Eclipse titled Lab 21_8. This PDF document is included in the project in the doc directory. The Java files you will use in this lab are in the src directory.

Copy over RunShop.java and Cheese.java from the previous lab. Your program must produce an output matching the sample runs given below.

Part 1: Modify RunShop.java (version 2)

In the original RunShop.java (from previous lab), we are creating an instance of Shop class named shop. Then we call the method run() of this shop object. Now we no longer have an object or class called Shop and instead, we will be using ShopArr. Import RunShop.java from the previous lab to do this step.

[Answer assessment question 1]

Make the change in RunShop.java file which will allow you to run the newest cheese shop. (same as answer to Q1)

Part 2: Fill-in ShopArr.java

Everywhere you see comment to Fill in Code is where you need to add code to make this program behave correctly. If it says Fix Code you need to change existing code. In most places a sample is provided to help you get started. The program currently runs but the behavior is obviously incorrect.

Here is a simpler version of intro() as reference

public static void intro(String[] names, double[]prices, int[] amounts) {

// Special 3 Cheeses if (names.length > 0) { names[0] = Humboldt Fog; prices[0] = 25.00;

}

if (names.length > 1) { names[1] = Red Hawk ;

prices[1] = 40.50;

}

if (names.length > 2) { names[2] = Teleme;

prices[2] = 17.25;

} Random ranGen = new Random(100);

System.out.println(We sell + names.length + kinds of Cheese); if (names.length > 0)

System.out.println(names[0] + : $ + prices[0] + per pound); if (names.length > 1)

System.out.println(names[1] + : $ + prices[1] + per pound); if (names.length > 2)

System.out.println(names[2] + : $ + prices[2] + per pound);

for (int i = 3; i < names.length; i++) { names[i] = Cheese Type + (char)(A+i); prices[i] = ranGen.nextInt(1000)/100.0;

amounts[i] = 0;

System.out.println(names[i] + : $ + prices[i] + per pound);

}

}

We must now split this method into two methods for this lab: init() and intro(). The reason is because we want to repeat intro() if needed, but creating objects using init() needs to be done only once. So all the println statements will be moved to intro(). Now take a look at ShopArr.java and the init() method in it. We see the code is very similar but the variables have changed. The very first thing we do is create the array of Cheese pointers since we are given the argument max.

// Create max number of Cheese pointers cheese = new Cheese[max];

Then you will see the code to handle Humboldt Fog cheese:

if (max > 0) {

cheese[0] = new Cheese(); cheese[0].setName(Humboldt Fog);

cheese[0].setPrice(25.00);

}

Instead of names.length, we now use max in this code.

[Answer assessment question 2]

Also, instead of using three different arrays (names, prices and amounts), we now have only 1 array of cheeses. So the code is changed to use cheese[0] which points to the first Cheese object in the array. If we want to change the name then we use a mutator setName, which exists inside the Cheese object

(cheese[0]), that we access using the . operator. We instantiate Humboldt Fog using default constructor with 0 arguments followed by invoking two mutators. Red Hawk is instantiated with a 1-argument constructor followed by invoking only one mutator. And finally, Teleme uses a 2-argument constructor, so no mutator calls are necessary. Note that you must use the corresponding accessor method calls in other parts of the code to get to the value of the variables set by the mutators.

[Answer assessment questions 3, 4 and 5]

Now you will need to implement the for-loop in init(). The original loop is as follows:

for (int i = 3; i < names.length; i++) { names[i] = Cheese Type + (char)(A + i); prices[i] = ranGen.nextInt(1000)/100.0; amounts[i] = 0;

}

You must figure out the transformations needed in the for-loop to work with a single cheese array instead of 3 arrays, as shown by the code already inside init(). You can assume the amount is already set to 0 for each cheese so the loop doesnt need to set it again to 0.

[Answer assessment question 6]

We have also implemented the basic version of ShopArr constructor which just invokes init method with a fixed number, 10. You must fill-in the 1-argument constructor which will invoke init using the max parameter instead.

[Answer assessment question 7]

Now implement intro(Scanner), itemizedList(), calcSubTotal() and discountSpecials() so they work for an array of cheese pointer. The methods printSubTotals() and printFinalTotal() should be identical to Lab 07.

[Answer assessment questions 8 and 9]

Part 3: Modify RunShop.java (version 3)

Now notice that there are two constructors for ShopArr available and version 2 of RunShop (from Part 1) is only calling the default constructor with no arguments. So, the program will always create 10 cheeses to sell. We will need to make use of the second constructor which takes an argument max and sets the amount of cheeses to sell.

Modify RunShop so it asks the following question to the user and then pass the number user enters to the ShopArr constructor. So the program now starts as follows:

Enter the number of Cheeses for shop setup: 12

We sell 12 types of Cheese (in 0.5 lb packages)

Everything should work as it did before, now you can just change the number of cheese from 10 to any amount you want (including 0 but not negatives).

[Answer assessment question 10]

Part 4: (Assessment) Logic Check and Level of Understanding

Create a Word document or text file named Part4 that contains answers to the following:

• What are the minimal changes required to instantiate ShopArr and invoke run() on it?
• We can also use a <something>.length instead of max. What is the valid <something> to use in java?
• How can we tell which instantiation (new Cheese) corresponds to which constructor definition inside the Cheese class?
• How can we identify a mutator method call?
• What would be the result if we added this line right after Teleme is created: cheese[2].setName(Wrong Name); ?
• Why is the init() method both private and void?
• What are the distinguishing features of constructor methods? (i.e., How do we tell them apart from other methods?)
• How can we figure out the number of required iterations for each loop?
• Should we pass in Cheese array pointer (cheese[]) as arguments into calcSubTotal or itemizedList? (Why or why not)
• What value will be printed by RunShop for Ran with Cheese Total? (fixed number or a formula)

Sample Runs (user input shown in green, with each run separated by a dashed-line):

-SAMPLE RUN 11 Enter the number of Cheeses for shop setup: 02 We sell 0 kinds of Cheese (in 0.5 lb packages)345 Display the itemized list? (1 for yes): 1 6 No items were purchased.78 Original Sub Total: $0.009 Specials10 None -$0.011 New Sub Total: $0.0012 Additional 0% Discount: -$0.013 Final Total: $0.001415 Do you wish to redo your whole order? (1 for yes): 01617 Thanks for coming!18 Ran with Cheese Total: 0-SAMPLE RUN 21 Enter the number of Cheeses for shop setup: 12 We sell 1 kinds of Cheese (in 0.5 lb packages)3 Humboldt Fog: $25.0 per pound45 Enter the amount of Humboldt Fog in lb: 167 Display the itemized list? (1 for yes): 18 1.0 lb of Humboldt Fog @ $25.00 = $25.00 910 Original Sub Total: $25.0011 Specials12 Humboldt Fog (Buy 1 Get 1 Free): -$12.5013 New Sub Total: $12.5014 Additional 0% Discount: -$0.015 Final Total: $12.501617 Do you wish to redo your whole order? (1 for yes): 11819 We sell 1 kinds of Cheese (in 0.5 lb packages)20 Humboldt Fog: $25.0 per pound2122 Enter the amount of Humboldt Fog in lb: 02324 Display the itemized list? (1 for yes): 1 25 No items were purchased.2627 Original Sub Total: $0.0028 Specials29 None -$0.030 New Sub Total: $0.0031 Additional 0% Discount: -$0.032 Final Total: $0.003334 Do you wish to redo your whole order? (1 for yes): 03536 Thanks for coming!

37 Ran with Cheese Total: 1-SAMPLE RUN 31 Enter the number of Cheeses for shop setup: 42 We sell 4 kinds of Cheese (in 0.5 lb packages)3 Humboldt Fog: $25.0 per pound4 Red Hawk: $40.5 per pound5 Teleme: $17.25 per pound6 Cheese Type D: $9.15 per pound78 Enter the amount of Humboldt Fog in lb: 4.59 Enter the amount of Red Hawk in lb: 4.510 Enter the amount of Teleme in lb: -311 Invalid input. Enter a value >= 0: 1.712 Invalid input. Enter a value thats multiple of 0.5: -413 Invalid input. Enter a value >= 0: 1.914 Invalid input. Enter a value thats multiple of 0.5: 1.5 15 Enter the amount of Cheese Type D in lb: 10 1617 Display the itemized list? (1 for yes): 118 4.5 lb of Humboldt Fog @ $25.00 = $112.5019 4.5 lb of Red Hawk @ $40.50 = $182.2520 1.5 lb of Teleme @ $17.25 = $25.8821 10.0 lb of Cheese Type D @ $9.15 = $91.50 2223 Original Sub Total: $412.1324 Specials25 Humboldt Fog (Buy 1 Get 1 Free): -$50.0026 Red Hawk (Buy 2 Get 1 Free): -$60.7527 New Sub Total: $301.3828 Additional 15% Discount: -$75.3429 Final Total: $226.033031 Do you wish to redo your whole order? (1 for yes): 03233 Thanks for coming!34 Ran with Cheese Total: 4-SAMPLE RUN 41 Enter the number of Cheeses for shop setup: 122 We sell 12 kinds of Cheese (in 0.5 lb packages)3 Humboldt Fog: $25.0 per pound4 Red Hawk: $40.5 per pound5 Teleme: $17.25 per pound6 Cheese Type D: $9.15 per pound 7 Cheese Type E: $2.5 per pound8 Cheese Type F: $8.74 per pound9 Cheese Type G: $9.88 per pound10 Cheese Type H: $2.91 per pound11 Cheese Type I: $6.66 per pound12 Cheese Type J: $0.36 per pound13 Cheese Type K: $2.88 per pound14 Cheese Type L: $7.23 per pound1516 Enter the amount of Humboldt Fog in lb: 1.517 Enter the amount of Red Hawk in lb: 2.218 Invalid input. Enter a value thats multiple of 0.5: 2.519 Enter the amount of Teleme in lb: 020 Enter the amount of Cheese Type D in lb: 021 Enter the amount of Cheese Type E in lb: 022 Enter the amount of Cheese Type F in lb: 023 Enter the amount of Cheese Type G in lb: 824 Enter the amount of Cheese Type H in lb: 10

25 Enter the amount of Cheese Type I in lb: 026 Enter the amount of Cheese Type J in lb: 027 Enter the amount of Cheese Type K in lb: 028 Enter the amount of Cheese Type L in lb: 0 2930 Display the itemized list? (1 for yes): 131 1.5 lb of Humboldt Fog @ $25.00 = $37.5032 2.5 lb of Red Hawk @ $40.50 = $101.2533 8.0 lb of Cheese Type G @ $9.88 = $79.0434 10.0 lb of Cheese Type H @ $2.91 = $29.10 3536 Original Sub Total: $246.8937 Specials38 Humboldt Fog (Buy 1 Get 1 Free): -$12.5039 Red Hawk (Buy 2 Get 1 Free): -$20.2540 New Sub Total: $214.1441 Additional 10% Discount: -$21.4142 Final Total: $192.734344 Do you wish to redo your whole order? (1 for yes): 14546 We sell 12 kinds of Cheese (in 0.5 lb packages)47 Humboldt Fog: $25.0 per pound48 Red Hawk: $40.5 per pound49 Teleme: $17.25 per pound50 Cheese Type D: $9.15 per pound51 Cheese Type E: $2.5 per pound52 Cheese Type F: $8.74 per pound53 Cheese Type G: $9.88 per pound54 Cheese Type H: $2.91 per pound55 Cheese Type I: $6.66 per pound56 Cheese Type J: $0.36 per pound57 Cheese Type K: $2.88 per pound58 Cheese Type L: $7.23 per pound5960 Enter the amount of Humboldt Fog in lb: 061 Enter the amount of Red Hawk in lb: 062 Enter the amount of Teleme in lb: 1263 Enter the amount of Cheese Type D in lb: 064 Enter the amount of Cheese Type E in lb: 165 Enter the amount of Cheese Type F in lb: 266 Enter the amount of Cheese Type G in lb: 367 Enter the amount of Cheese Type H in lb: 068 Enter the amount of Cheese Type I in lb: 069 Enter the amount of Cheese Type J in lb: 570 Enter the amount of Cheese Type K in lb: 071 Enter the amount of Cheese Type L in lb: -372 Invalid input. Enter a value >= 0: 1.173 Invalid input. Enter a value thats multiple of 0.5: 4 7475 Display the itemized list? (1 for yes): 0 7677 Original Sub Total: $287.3478 Specials79 None -$0.080 New Sub Total: $287.3481 Additional 15% Discount: -$71.8482 Final Total: $215.518384 Do you wish to redo your whole order? (1 for yes): 0

• Thanks for coming!
• Ran with Cheese Total: 12

Specification Compliance

The following are some additional instructions to make sure your project complies with specifications:

1. Your program must produce an output that exactly resembles the Sample Output shown above, including identical wording of prompts, spacing, input locations, etc.
2. Your program must ensure the following:
   1. Your program should not display items that are not bought (amount is 0) when listing them out [cf.

Sample Run 4, Lines 31-34]. If no items are purchased, then a special message is displayed [cf. Sample Run 2, Line 35].

1. If no discounts are applied, a special message is displayed [cf. Sample Run 4, Line 79].

3. Your program must check for invalid inputs when entering the amounts [cf. Sample Run 3, Lines 8-15].
4. Before you submit, in Eclipse, type CTRL-A (to select everything) followed by a CTRL-I (to fix indentation) on each of your java programs. In MacOS the corresponding keystrokes are Cmd-A followed by Cmd-I.