Chapter 3 Lab DecisionStructures

Chapter 3 Lab DecisionStructures

Lab Objectives

Be able to construct boolean expressions to evaluate a given condition
Be able to compare Stringobjects
Be able to usea flag
Be able to constructif and if-else-if statements to perform a specific task
Be able to construct a switch statement
Be able to format output

Introduction

Up to this point, all the programs you have written had a sequence structure. This means that all statements are executed in sequence, one after another. Sometimes we need to let the computer make decisions, based on the data. A decision structure allows the computer to decidewhich statement to execute.

In order to have the computer make a decision, it needs to do a comparison. So we will work with writingboolean expressions. boolean expressions use relationaloperators and logicaloperators to create a condition that can be evaluated as true or false.

Once we have a condition, we can conditionally execute statements. This means that there are statements in the program that may or may not be executed, depending on thecondition.

We can also chain conditional statements together to allow the computer to choose from several courses of action. We will explore this using nested if-else statements as well as a switch statement.

In this lab, we will be editing a pizza ordering program. It creates a pizza ordered to the specifications that the user desires. It walks the user through ordering, giving the user choices, which the program then uses to decide how to make the pizza and how much the cost of the pizza will be. The user will also receive a $2.00 discount if his or her name is Mike or Diane.

Task #1 The if Statement, Comparing Strings, and Flags

Copy the file PizzaOrder.java (see Code Listing3.1) from the Student Files or as directed by your instructor.
Compile and run PizzaOrder.java. You will be able to make selections, but at this point, you will always get a Hand-tossed pizza at a base cost of $12.99 no matter what you select, but you will be able to choose toppings, and they should

add into the price correctly. You will also notice that the output does not look like money. So we need to edit PizzaOrder.java to complete the program so that it works correctly.

Construct a simple if statement. The condition will compare the String input by the user as his or her first name with the first names of the owners, Mike and Diane.Be sure that the comparison is not casesensitive.
If the user haseither first name, set the discount flag to true. This will not affect the price at thispoint yet.

Task #2 The if-else-if Statement

an if-else-if statement that lets the computer choose which statements to execute by the user input size (10, 12, 14, or 16). For each option, the cost needs to beset to the appropriate amount.
The default else of the above if-else-if statement should print a statement that the user input was not one of the choices, so a 12 inch pizza will be made. Itshould also set the pizza size to 12 and the cost to 12.99.
Compile, debug, and run. You should now be able to get correct output for the pizza size and price (it will still have Hand-tossed crust, the output won’t look like money, and no discount will be applied yet). Runyour program multiple times ordering a 10, 12, 14, 16, and 17 inch pizza.

Task #3 The switch Statement

switch statement that compares the user’s choice with the appropriate characters (make sure that both capital letters and small letters will work).
Each case will assign the appropriate string indicating crust type to the crust variable.
The default case will print a statement that the user input was not one of the choices, so a Hand-tossed crust will be made.
Compile, debug, and run. You should now be able to get crust types other than Hand-tossed. Run your program multiple times to make sure all cases of the switch statement operate correctly.

Task #4 Using aFlag as a Condition

an if statement that uses the flag as the condition. Remember that the flag is a boolean variable, therefore is true or false. It does not have to be compared to anything.
The body of the if statement should contain two statements:
A statement that prints a message indicatingthat the user is eligiblefor a
$2.00 discount.

A statement that reduces the variablecost by 2.

Compile, debug, and run. Test your program using the owners’ names (both capitalized and not) as well as a different name. The discount should be displayed correctlyat this time.

Task #5 Formatting Output

Edit the appropriate lines in the main method so that any monetary output has 2 decimal places.
Compile, debug, and run. Your output should be completely correct at this time, and numeric output should look like money.

Code Listing 3.1 (PizzaOrder.java)

import java.util.Scanner; // Needed for the Scannerclass

/**

Thisprogram allows the user to order a pizza.

*/

publicclass PizzaOrder

{

publicstatic void main (String[] args)

{

// Create a Scanner object to read input. Scanner keyboard= new Scanner (System.in);

StringfirstName; // User’s first name boolean discount = false; // Flag for discount int inches; // Size of the pizza

charcrustType; // For type of crust String crust = “Hand-tossed”; // Name of crust double cost = 12.99; // Cost of the pizza final double TAX_RATE = .08; // Sales tax rate double tax; // Amount of tax

char choice; // User’schoice

Stringinput; // User input Stringtoppings = “Cheese “; // List of toppings

int numberOfToppings = 0; // Number of toppings

// Prompt user and get first name. System.out.println(“Welcome to Mike and ” +

“Diane’s Pizza”); System.out.print(“Enter your first name: “); firstName = keyboard.nextLine();

// Determine if user is eligible for discount by

// having the same first name as one of the owners.

// ADD LINES HERE FOR TASK #1

// Prompt user and get pizza size choice. System.out.println(“Pizza Size (inches) Cost”);System.out.println(” 10 $10.99″);

System.out.println(” 12 $12.99″);

System.out.println(” 14 $14.99″);

System.out.println(” 16 $16.99″); System.out.println(“Whatsize pizza “+

“would you like?”); System.out.print(“10, 12, 14, or 16 “+

“(enter the number only): “); inches= keyboard.nextInt();

// Set price and size of pizza ordered.

// ADD LINES HERE FOR TASK #2

// Consumethe remaining newlinecharacter. keyboard.nextLine();

// Prompt user and get crust choice. System.out.println(“What type of crust ” +

“do you want? “); System.out.print(“(H)Hand-tossed, “+

“(T) Thin-crust, or “+

“(D) Deep-dish ” + “(enter H, T, or D): “);

input = keyboard.nextLine(); crustType = input.charAt(0);

// Set user’s crustchoice on pizzaordered.

// ADD LINES FOR TASK #3

// Promptuser and get topping choicesone at a time. System.out.println(“All pizzas come with cheese.”); System.out.println(“Additional toppingsare ” +

“$1.25 each, choose from:”); System.out.println(“Pepperoni, Sausage,” +

“Onion, Mushroom”);

// If topping is desired,

// add to topping list and number of toppings System.out.print(“Do you want Pepperoni? (Y/N): “); input= keyboard.nextLine();

choice= input.charAt(0);

if (choice == ‘Y’ || choice == ‘y’)

{

numberOfToppings += 1;

toppings = toppings + “Pepperoni “;

}

System.out.print(“Do you want Sausage?(Y/N): “); input= keyboard.nextLine();

choice= input.charAt(0);

if (choice == ‘Y’ || choice == ‘y’)

{

numberOfToppings += 1;

toppings = toppings + “Sausage “;

}

System.out.print(“Do you want Onion? (Y/N): “);input = keyboard.nextLine();

choice= input.charAt(0);

if (choice == ‘Y’ || choice == ‘y’)

{

numberOfToppings += 1;

toppings = toppings + “Onion “;

}

System.out.print(“Do you want Mushroom?(Y/N): “); input= keyboard.nextLine();

choice= input.charAt(0);

if (choice == ‘Y’ || choice == ‘y’)

{

numberOfToppings += 1;

toppings = toppings + “Mushroom “;

}

// Add additional toppingscost to cost of pizza.cost = cost + (1.25* numberOfToppings);

// Display order confirmation. System.out.println();

System.out.println(“Your order is as follows: “);System.out.println(inches + ” inch pizza”); System.out.println(crust + ” crust”); System.out.println(toppings);

// Applydiscount if user is eligible.

// ADD LINES FOR TASK #4 HERE

// EDIT PROGRAMFOR TASK #5

// SO ALL MONEY OUTPUTAPPEARS WITH 2 DECIMAL PLACES

System.out.printf(“The cost of your order ” +

“is: $%f\n”, cost);

// Calculate and display tax and total cost. tax = cost * TAX_RATE; System.out.printf(“The tax is: $%f\n”, tax); System.out.printf(“The totaldue is: $%f\n”,

(tax + cost));

System.out.println(“Your orderwill be ready” +

“for pickupin 30 minutes.”);

}

}