Starting Out with Java: From Control Structures through Objects 5 th edition By Tony Gaddis Source Code: Chapter 8

Code Listing 8-1 (Countable.java) 1 /** 2 This class demonstrates a static field. 3 */ 4 5 public class Countable 6 { 7 private static int instanceCount = 0; // What category of variable? 8 // What is it’s scope? 9 /** 10 The constructor increments the static 11 field instanceCount. This keeps track 12 of the number of instances of this 13 class that are created. 14 */ public Countable() 17 { 18 instanceCount ++; 19 } 20 (Continued)

21 /** 22 The getInstanceCount method returns 23 the number of instances of this class 24 that have been created. The value in the instanceCount field. 26 */ public int getInstanceCount() 29 { 30 return instanceCount; 31 } 32 }

Code Listing 8-2 (StaticDemo.java) 1 /** 2 This program demonstrates the Countable class. 3 */ 4 5 public class StaticDemo 6 { 7 public static void main (String[] args) 8 { 9 int objectCount; 10 11// Create three instances 13 Countable object1 = new Countable(); 14 Countable object2 = new Countable(); 15 Countable object3 = new Countable(); objectCount = object1.getInstanceCount(); 20 System.out.println(objectCount + 21 " instances of the class " + 22 "were created."); 23 } 24 } Program Output 3 instances of the class were created.

Code Listing 8-3 (Metric.java) 1 /** 2 This class demonstrates static methods. 3 */ 4 5 public class Metric 6 { 7 /** 8 The milesToKilometers method converts a 9 distance in miles to kilometers. m The distance in miles. The distance in kilometers. 12 */ public static double milesToKilometers( double m ) 15 { 16 return m * 1.609; 17 } 18 (Continued)

(Continued) Code Listing 8-3 (Metric.java) 19 /** 20 The kilometersToMiles method converts 21 a distance in kilometers to miles. k The distance in kilometers. The distance in miles. 24 */ public static double kilometersToMiles( double k ) 27 { 28 return k / 1.609; 29 } 30 }

Code Listing 8-4 (MetricDemo.java) 1 import javax.swing.JOptionPane; 2 import java.text.DecimalFormat; 3 4 /** 5 This program demonstrates the Metric class. 6 */ 7 8 public class MetricDemo 9 { 10 public static void main (String[] args) 11 { 12 String input; 13 double miles; 14 double kilos; DecimalFormat fmt = new DecimalFormat("0.00"); input = JOptionPane.showInputDialog (" Enter " + 22 " a distance in miles."); 23 miles = Double.parseDouble(input); (Continued)

26 kilos = Metric. milesToKilometers(miles); // Invoked thru? 27 JOptionPane.showMessageDialog(null, 28 fmt.format(miles) + " miles equals " + 29 fmt.format(kilos) + " kilometers."); input = JOptionPane.showInputDialog("Enter " + 33 " a distance in kilometers:"); 34 kilos = Double.parseDouble( input ); miles = Metric. kilometersToMiles (kilos); // Invoked thru? 38 JOptionPane.showMessageDialog(null, 39 fmt.format(kilos) + " kilometers equals " + 40 fmt.format(miles) + " miles."); System.exit(0); 43 } 44 }

Code Listing 8-5 (PassObject.java) 1 /** 2 This program passes an object as an argument. 3 */ 4 5 public class PassObject 6 { 7 public static void main (String[] args) 8 { 9 10 Rectangle box = new Rectangle(12.0, 5.0); // Pass a reference to the object to 13 // the displayRectangle method. 14 displayRectangle(box); // Where defined? 15 } /** 18 The displayRectangle method displays the 19 length and width of a rectangle. r A reference to a Rectangle 21 object. 22 */ (Continued)

23 24 public static void displayRectangle(Rectangle r ) 25 { 26 // Display the length and width. 27 System.out.println("Length : " + r.getLength() + // Calls an Instance Method 28 " Width : " + r.getWidth()); // from a static method 29 } 30} Program Output Length : 12.0 Width : 5.0

Code Listing 8-6 (PassObject2.java) 1 /** 2 This program passes an object as an argument. 3 The object is modified by the receiving method. 4 */ 5 6 public class PassObject2 7 { 8 public static void main (String[] args) 9 { Rectangle box = new Rectangle(12.0, 5.0); System.out.println(" Contents of the box object :"); 15 System.out.println("Length : " + box.getLength() + 16 " Width : " + box.getWidth()); // Pass a reference to the object to the 19 // changeRectangle method. 20 changeRectangle(box); (Continued)

23 System.out.println("\nNow the contents of the " + 24 " box object are:"); 25 System.out.println("Length : " + box.getLength() + 26 " Width : " + box. getWidth()); 27 } /** 30 The changeRectangle method sets a Rectangle 31 object's length and width to 0. r The Rectangle object to change. 33 */ public static void changeRectangle ( Rectangle r ) 36 { 37 r.setLength(0.0); 38 r.setWidth(0.0); 39 } 40 } Program Output Contents of the box object: Length : 12.0 Width : 5.0 Now the contents of the box object are: Length : 0.0 Width : 0.0

Code Listing 8-7 (ReturnObject.java) 1 import javax.swing.JOptionPane; 2 3 /** 4 This program demonstrates how a method 5 can return a reference to an object. 6 */ 7 8 public class ReturnObject 9 { 10 public static void main (String[] args) 11 { 12 BankAccount account; account = getAccount(); // Returns what? JOptionPane.showMessageDialog(null, 19 "The account has a balance of $" + 20 account.getBalance()); System.exit(0); 23 } (Continued)

24 25 /** 26 The getAccount method creates a BankAccount 27 object with the balance specified by the 28 user. A reference to the object. 30 */ public static BankAccount getAccount() 33 { 34 String input; // To hold input 35 double balance; // Account balance input = JOptionPane.showInputDialog(" Enter " + 39 "the account balance."); 40 balance = Double.parseDouble( input ); return new BankAccount(balance); 45 } 46 }

Code Listing 8-8 (Stock.java) 1 /** 2 The Stock class holds data about a stock. 3 */ 4 5 public class Stock 6 { 7 private String symbol; // Trading symbol of stock 8 private double sharePrice ; // Current price per share 9 10 /** 11 Constructor sym The stock's trading symbol. price The stock's share price. 14 */ public Stock ( String sym, double price ) 17 { 18 symbol = sym ; 19 sharePrice = price ; 20 } 21 (Continued)

22 /** 23 getSymbol method The stock's trading symbol. 25 */ public String getSymbol() 28 { 29 return symbol; 30 } /** 33 getSharePrice method The stock's share price 35 */ public double getSharePrice() 38 { 39 return sharePrice; 40 } 41 (Continued)

42 /** 43 toString method A string indicating the object's 45 trading symbol and share price. 46 */ public String toString() // EXPLICIT toString() 49 { 50 // Create a string describing the stock. 51 String str = "Trading symbol: " + symbol + 52 "\nShare price: " + sharePrice; return str; 56 } 57 }

Code Listing 8-9 (StockDemo1.java) 1 /** 2 This program demonstrates the Stock class's 3 toString method. 4 */ 5 6 public class StockDemo1 7 { 8 public static void main ( String[] args) 9 { 10 // Create a Stock object for the XYZ Company Stock xyzCompany = new Stock ("XYZ", 9.62); // Display the object's values. 16 System.out.println(xyzCompany) ; // What method is called? 17 } 18 } // Auto call under what 2 // conditions? Program Output Trading symbol: XYZ Share price: 9.62

Code Listing 8-10 (StockCompare.java) 1 /** 2 This program uses the Stock class's equals 3 method to compare two Stock objects. See for “equals”. 4 */ 5 6 public class StockCompare 7 { 8 public static void main ( String[] args) 9 { 11 Stock company1 = new Stock("XYZ", 9.62); 12 Stock company2 = new Stock("XYZ", 9.62); if (company1.equals(company2)) 16 System.out.println("Both objects are the same."); 17 else 18 System.out.println("The objects are different."); 19 } 20} Program Output Both objects are the same.

Code Listing 8-11 (ObjectCopy.java) 1 /** 2 This program uses the Stock class's copy method 3 to create a copy of a Stock object. ( see pg. 517) 4 */ 5 6 public class ObjectCopy 7 { 8 public static void main (String[] args) 9 { 11 Stock company1 = new Stock("XYZ", 9.62); Stock company2; // copy()- makes a new stock object-uses IV’s of company1. 17 // returns addr of new object 17 company2 = company1.copy(); // Display the contents of both objects. 21 System.out.println("Company 1:\n" + company1 ); // Calls toString() // implicitly 22 System.out.println(); 23 System.out.println("Company 2:\n" + company2 ); (Continued)

24 25 // Confirm that we actually have two objects. 26 if (company1 == company2) 27 { 28 System.out.println("The company1 and company2 " + 29 "variables reference the same object."); 30 } 31 else 32 { 33 System.out.println("The company1 and company2 " + 34 "variables reference different objects."); 35 } 36 } 37 } Program Output Company 1: Trading symbol: XYZ Share price: 9.62 Company 2: Trading symbol: XYZ Share price: 9.62 The company1 and company2 variables reference different objects.

Code Listing 8-12 (Instructor.java) 1 /** 2 This class stores data about an instructor. 3 */ 4 5 public class Instructor 6 { 7 private String lastName ; // Last name 8 private String firstName; // First name 9 private String officeNumber; // Office number /** 12This constructor initializes the last name, 13 first name, and office number. lname The instructor's last name. fname The instructor's first name. office The office number. 17 */ public Instructor (String lname, String fname, 20 String office) (Continued)

21 { 22 lastName = lname; 23 firstName = fname; 24 officeNumber = office; 25 } /** 28 The copy constructor initializes the object 29 as a copy of another Instructor object. object2 The object to copy. 31 */ public Instructor ( Instructor object2 ) 34 { 35 lastName = object2.lastName; 36 firstName = object2.firstName; 37 officeNumber = object2.officeNumber; 38 } /** 41 The set method sets a value for each field. lname The instructor's last name. (Continued)

fname The instructor's first name. office The office number. 45 */ public void set ( String lname, String fname, 48 String office) 49 { 50 lastName = lname; 51 firstName = fname; 52 officeNumber = office; 53 } /** 56 toString method A string containing the instructor 58 information. 59 */ 60 (Continued)

61 public String toString() 62 { 63 // Create a string representing the object. 64 String str = "Last Name: " + lastName + 65 "\nFirst Name: " + firstName + 66 "\nOffice Number: " + officeNumber; return str; 70 } 71 }

Code Listing 8-13 (TextBook.java) 1 /** 2 This class stores data about a textbook. 3 */ 4 5 public class TextBook 6 { 7 private String title; // Title of the book 8 private String author; // Author's last name 9 private String publisher; // Name of publisher /** 12 This constructor initializes the title, 13 author, and publisher fields textTitle The book's title. auth The author's name. pub The name of the publisher. 17 */ public TextBook (String textTitle, String auth, 20 String pub) 21 { 22 title = textTitle; 23 author = auth; (Continued)

24 publisher = pub; 25 } /** 28 The copy constructor initializes the object 29 as a copy of another TextBook object. object2 The object to copy. 31 */ public TextBook ( TextBook object2 ) 34 { 35 title = object2.title; 36 author = object2.author; 37 publisher = object2.publisher; 38 } /** 41 The set method sets a value for each field. textTitle The book's title. auth The author's name. pub The name of the publisher. 45 */ public void set (String textTitle, String auth, (Continued)

48 String pub) 49 { 50 title = textTitle; 51 author = auth; 52 publisher = pub; 53 } /** 56 toString method A string containing the textbook 58 information. 59 */ public String toString() 62 { 63 // Create a string representing the object. 64 String str = "Title: " + title + 65 "\nAuthor: " + author + 66 "\nPublisher: " + publisher; return str; 70 } 71 }

Code Listing 8-14 (Course.java) 1 /** 2 This class stores data about a course. Aggregate data. 3 */ 4 5 public class Course 6 { 7 private String courseName; // Name of the course 8 private Instructor instructor; // Course “has an” instructor 9 private TextBook textBook; // Course “has a” textbook /** 12 This constructor initializes the courseName, 13 instructor, and text fields. name The name of the course. instructor An Instructor object. text A TextBook object. 17 */ public Course ( String name, Instructor instr, 20 TextBook text ) 21 { 22 // Assign the courseName. 23 courseName = name; (Continued)

24 25 // Init IV with a “deep copy” of the parameter object instructor = new Instructor(instr); // Init IV with a “deep copy” of the parameter object textBook = new TextBook(text); 32 } /** 35 getName method The name of the course. 37 */ public String getName() 40 { 41 return courseName; 42 } /** 45 getInstructor method A reference to a copy of this course's (Continued)

47 Instructor object. 48 */ public Instructor getInstructor() 51 { 52 // Return a copy of the instructor object. 53 return new Instructor(instructor); // Returns a copy of object, not 54 } // reference to the object. 55 // See , “Shallow” copy and security 56 /** 57 getTextBook method A reference to a copy of this course's 59 TextBook object. 60 */ public TextBook getTextBook() 63 { 64 // Return a copy of the textBook object. 65 return new TextBook(textBook); // Same as comments above. 66 } /** 69 toString method (Continued)

A string containing the course information. 71 */ public String toString() 74 { 75 // Create a string representing the object. 76 String str = "Course name: " + courseName + 77 "\nInstructor Information:\n" + 78 instructor + 79 "\nTextbook Information:\n" + 80 textBook; 81 // “courseName” - String IV 82 // “instructor” - Instructor class toString() // “textBook” - Textbook class toString() 83 return str; 84 } 85 }

Code Listing 8-15 (CourseDemo.java) 1 /** 2 This program demonstrates the Course class. 3 */ 4 5 public class CourseDemo 6 { 7 public static void main (String[] args) 8 { 9 // Create an Instructor object. 10 Instructor myInstructor = new Instructor("Kramer", "Shawn", "RH3010"); // Create a TextBook object. 14 TextBook myTextBook = new TextBook("Starting Out with Java", 16 "Gaddis", "Addison-Wesley"); // Create a Course object. 19 Course myCourse = new Course("Intro to Java", myInstructor, myTextBook); // Display the course information. (Continued)

24 System.out.println(myCourse); // Implicit call to ? 25 } 26 Program Output Course name : Intro to Java Instructor Information: Last Name: Kramer First Name: Shawn Office Number: RH3010 Textbook Information: Title: Starting Out with Java Author: Gaddis Publisher: Addison-Wesley

Code Listing 8-16 (FullName.java) 1 /** 2 This class stores a person's first, last, and middle 3 names. The class is dangerous because it does not 4 prevent operations on null reference fields. 5 NOTE: No explicit constructor 5 */ 6 7 public class FullName 8 { 9 private String lastName; // Last name 10 private String firstName; // First name 11 private String middleName; // Middle name /** 14 The setLastName method sets the lastName field. str The String to set lastName to. 16 */ public void setLastName (String str) 19 { 20 lastName = str; 21 } /** (Continued)

24 The setFirstName method sets the firstName field. str The String to set firstName to. 26 */ public void setFirstName (String str) 29 { 30 firstName = str; 31 } /** 34 The setMiddleName method sets the middleName field. str The String to set middleName to. 36 */ public void setMiddleName (String str) 39 { 40 middleName = str; 41 } /** 44 The getLength method returns the length of the 45 full name. The length. (Continued)

47 */ public int getLength() 50 { 51 return lastName.length() + firstName.length() 52 + middleName.length(); 53 } /** 56 The toString method returns the full name. A reference to a String. 58 */ public String toString() 61 { 62 return firstName + " " + middleName + " " 63 + lastName; 64 } 65 }

Code Listing 8-17 (NameTester.java) 1 /** 2 This program creates a FullName object, and then 3 calls the object's getLength method before values 4 are established for its reference fields. As a 5 result, this program will crash. 6 */ 7 8 public class NameTester 9 { 10 public static void main (String[] args) 11 { 12 int len ; // To hold the name length // Create a FullName object. 15 FullName name = new FullName(); // Get the length of the full name. 18 len = name.getLength(); // Will cause crash! Why? 19 } 20 }

Code Listing 8-18 (EnumDemo.java) 1 /** 2 This program demonstrates an enumerated type. 3 */ 4 5 public class EnumDemo 6 { 7 8 enum Day { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, 9 THURSDAY, FRIDAY, SATURDAY } public static void main (String[] args) 12 { Day workDay = Day. WEDNESDAY; System.out.println(workDay); System.out.println(" The ordinal value for " + 22 Day.SUNDAY + " is " + 23 Day. SUNDAY. ordinal()); (Continued)

24 27 System.out.println ("The ordinal value for " + 28 Day.SATURDAY + " is " + 29 Day.SATURDAY.ordinal()); if ( Day.FRIDAY. compareTo (Day.MONDAY ) > 0 ) 33 System.out.println( Day. FRIDAY + " is greater than " + 34 Day. MONDAY ); 35 else 36 System.out.println( Day. FRIDAY + " is NOT greater than " + 37 Day. MONDAY ); 38 } 39 } Program Output WEDNESDAY The ordinal value for SUNDAY is 0 The ordinal value for SATURDAY is 6 FRIDAY is greater than MONDAY

Code Listing 8-19 (CarType.java) 1 /** 2 CarType enumerated data type 3 */ 4 5 enum CarType { PORSCHE, FERRARI, JAGUAR }

Code Listing 8-20 (CarColor.java) 1 /** 2 CarColor enumerated data type 3 */ 4 5 enum CarColor { RED, BLACK, BLUE, SILVER }

Code Listing 8-21 (SportsCar.java) 1 import java.text.DecimalFormat; 2 3 /** 4 SportsCar class 5 */ 6 7 public class SportsCar 8 { 9 private CarType make ; // The car's make 10 private CarColor color ; // The car's color 11 private double price ; // The car's price /** 14 The constructor initializes the car's make, 15 color, and price. aMake The car's make. aColor The car's color. aPrice The car's price. 19 */ public SportsCar ( CarType aMake, CarColor aColor, 22 double aPrice ) 23 { (Continued)

24 make = aMake; 25 color = aColor; 26 price = aPrice ; 27 } /** 30 getMake method The car's make. 32 */ public CarType getMake() 35 { 36 return make ; 37 } /** 40 getColor method The car's color. 42 */ public CarColor getColor() 45 { 46 return color; (Continued)

47 } /** 50 getPrice method The car's price. 52 */ public double getPrice() 55 { 56 return price; 57 } /** 60 toString method A string indicating the car's make, 62 color, and price. 63 */ public String toString() 66 { 67 // Create a DecimalFormat object for 68 // dollar formatting. 69 DecimalFormat dollar = new DecimalFormat("#,##0.00"); (Continued)

70 71 // Create a string representing the object. 72 String str = "Make: " + make + 73 "\nColor: " + color + 74 "\nPrice: $" + dollar.format(price); // Return the string. 77 return str; 78 } 79 }

Code Listing 8-22 (SportsCarDemo.java) 1 /** 2 This program demonstrates the SportsCar class. 3 */ 4 5 public class SportsCarDemo 6 { 7 public static void main( String[] args) 8 { 9 // Create a SportsCar object. 10 SportsCar yourNewCar = new SportsCar (CarType. PORSCHE, 11 CarColor. RED, ); System.out.println(yourNewCar); 15 } 16 } Program Output Make: PORSCHE Color: RED Price: $100,000.00

Code Listing 8-23 (SportsCarDemo2.java) 1 /** 2 This program shows that you can switch on an 3 enumerated type. 4 */ 5 6 public class SportsCarDemo2 7 { 8 public static void main( String[] args) 9 { SportsCar yourNewCar = new SportsCar(CarType.PORSCHE, 12 CarColor.RED, ); switch ( yourNewCar. getMake() ) 16 { 17 case PORSCHE : 18 System.out.println("Your car was made in Germany."); 19 break; 20 case FERRARI : 21 System.out.println("Your car was made in Italy."); 22 break; 23 case JAGUAR :

24 System.out.println("Your car was made in England."); 25 break; 26 default: 27 System.out.println("I'm not sure where that car " 28 + "was made."); 29 } 30 } 31} Program Output Your car was made in Germany.

Code Listing 8-24 (StockPurchase.java) 1 /** 2 The StockPurchase class represents a stock purchase. 3 Class collaboration. Uses Stock class. 3 */ 4 5 public class StockPurchase 6 { 7 private Stock stock; // The stock that was purchased 8 private int shares ; // Number of shares owned 9 10 /** 11 Constructor stockObject The stock to purchase. numShares The number of shares. 14 */ public StockPurchase ( Stock stockObject, int numShares ) 17 { 18 // Create a copy of the object referenced by 19 // stockObject. 20 stock = new Stock(stockObject) ; // Creates Stock object copy. 21 shares = numShares; 22 } 23 (Continued)

24 /** 25 getStock method A copy of the Stock object for the stock 27 being purchased. 28 */ public Stock getStock() 31 { 32 // Return a copy of the object referenced by stock. 33 return new Stock(stock); // Invoke Stock class copy constructor 34 } /** 37 getShares method The number of shares being purchased. 39 */ public int getShares() 42 { 43 return shares; 44 } /** (Continued)

47 getCost method The cost of the stock purchase. 49 */ public double getCost() 52 { 53 return shares * stock.getSharePrice(); // Invokes Stock method. 54 } 55 }

Code Listing 8-25 (StockTrader.java) 1 import java.util.Scanner; 2 3 /** 4 This program allows you to purchase shares of XYZ 5 company's stock. 6 */ 7 8 public class StockTrader 9 { 10 public static void main (String[] args) 11 { 12 int sharesToBuy ; // Number of shares to buy // Create a Stock object for the company stock. 16 // The trading symbol is XYZ and the stock is // currently $9.62 per share. 17 Stock xyzCompany = new Stock("XYZ", 9.62); Scanner keyboard = new Scanner(System.in); // Display the current share price. 23 System.out. printf ("XYZ stock is currently $%,.2f.\n", (Continued)

24 xyzCompany.getSharePrice()); // Get the number of shares to purchase. 27 System.out.print("How many shares do you want to buy? "); 28 sharesToBuy = keyboard.nextInt(); // Create a StockPurchase object for the transaction. 31 StockPurchase buy = 32 new StockPurchase(xyzCompany, sharesToBuy); // Display the cost of the transaction. 35 System.out.printf("Cost of the stock: $%,.2f", 36 buy.getCost()); 37 } 38 } Program Output with Example Input Shown in Bold XYZ stock is currently $9.62. How many shares do you want to buy? 100 [Enter] Cost of the stock: $962.00