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

2. Code Listing 5-1 (SimpleMethod.java)
1 /**
2 This program defines and calls a simple method.
3 */
5 public class SimpleMethod
6 {
7 public static void main(String[] args)
8 {
9 System.out.println("Hello from the main method.");
10 displayMessage();
11 System.out.println("Back in the main method.");
12 } 14
18 public static void displayMessage()
19 {
20 System.out.println("Hello from the displayMessage method.");
21 }
22 }
Program Output
Hello from the main method.
Hello from the displayMessage method.
Back in the main method.

3. Code Listing 5-2 (LoopCall.java)
1 /**
2 This program defines and calls a simple method.
3 */ 4
5 public class LoopCall
6 {
7 public static void main(String[] args)
8 {
System.out.println("Hello from the main method.");
10 for (int i = 0; i < 5; i++)
displayMessage();
12 System.out.println("Back in the main method.");
13 } 14 15 18
19 public static void displayMessage()
20 {
21 System.out.println("Hello from the displayMessage method.");
22 }
23 }

4. Program Output
Hello from the main method.
Hello from the displayMessage method.
Back in the main method.

5. Code Listing 5-3 (CreditCard.java)
1 import javax.swing.JOptionPane;
3 /**
4 This program uses two void methods.
5 */ 6
7 public class CreditCard
8 {
9 public static void main(String[] args)
10 {
11 double salary; // Annual salary
12 int creditRating; // Credit rating
13 String input; // To hold the user’s input 14
// Get the user’s annual salary.
16 input = JOptionPane.showInputDialog(“What is " +
"your annual salary?");
18 salary = Double.parseDouble(input);
(Continued)

6. // Get the user’s credit rating (1 through 10). 19
// Get the user’s credit rating (1 through 10).
21 input = JOptionPane.showInputDialog(“On a scale of " +
22 "1 through 10, what is your credit rating?\n" +
23 "(10 = excellent, 1 = very bad)");
24 creditRating = Integer.parseInt(input); 25
// Determine whether the user qualifies.
27 if (salary >= && creditRating >= 7)
28 qualify();
29 else
30 noQualify(); 31
32 System.exit(0);
33 } 34
35 /**
36 The qualify method informs the user that he
37 or she qualifies for the credit card.
38 */
(Continued)

7. 40 public static void qualify() 41 { 39
40 public static void qualify()
41 {
42 JOptionPane.showMessageDialog(null, "Congratulations! " +
"You qualify for the credit card!");
44 } 45
46 /**
47 The noQualify method informs the user that he
48 or she does not qualify for the credit card.
49 */ 50
51 public static void noQualify()
52 {
53 JOptionPane.showMessageDialog(null, "I'm sorry. You " +
"do not qualify for the credit card.");
55 }
56 }

8. Code Listing 5-4 (DeepAndDeeper.java)
1 /**
2 This program demonstrates hierarchical method calls.
3 */ 4
5 public class DeepAndDeeper
6 {
7 public static void main(String[] args)
8 {
9 System.out.println("I am starting in main.");
10 deep();
11 System.out.println("Now I am back in main.");
12 } 13
14 /**
15 The deep method displays a message and then calls
16 the deeper method.
17 */ 18
(Continued)

9. Program Output 19 public static void deep() 20 {
20 {
21 System.out.println("I am now in deep.");
22 deeper();
23 System.out.println("Now I am back in deep.");
24 } 25
26 /**
27 The deeper method simply displays a message.
28 */ 29
30 public static void deeper()
31 {
32 System.out.println("I am now in deeper.");
33 }
34 }
Program Output
I am starting in main.
I am now in deep.
I am now in deeper.
Now I am back in deep.
Now I am back in main.

10. Code Listing 5-5 (PassArg.java)
1 /**
2 This program demonstrates a method with a parameter.
3 */ 4
5 public class PassArg
6 {
7 public static void main(String[] args)
8 {
9 int x = 10; 10
System.out.println("I am passing values to displayValue.");
displayValue(5);
displayValue(x);
14 displayValue( x * 4 );
15 displayValue( Integer.parseInt( "700") );
16 System.out.println("Now I am back in main.");
17 } 18
19 /**
20 The displayValue method displays the value
21 of its integer parameter.
22 */
(Continued)

11. 23
24 public static void displayValue( int num )
25 {
26 System.out.println("The value is " + num);
27 }
28 }
Program Output
I am passing values to displayValue.
The value is 5
The value is 10
The value is 40
The value is 700
Now I am back in main.

12. Code Listing 5-6 (PassByValue.java)
1 /**
2 This program demonstrates that only a copy of an argument
3 is passed into a method.
4 */ 5
6 public class PassByValue
7 {
8 public static void main(String[] args)
9 {
10 int number = 99; 11 12
13 System.out.println("number is " + number); 14
15 // Call changeMe, passing the value in number
// as an argument.
17 changeMe(number); 18
// Display the value in number again.
20 System.out.println("number is " + number);
21 } 22
(Continued)

13. 23 /**
24 The changeMe method accepts an argument and then
25 changes the value of the parameter.
26 */ 27
28 public static void changeMe( int myValue )
29 {
30 System.out.println("I am changing the value."); 31 32
33 myValue = 0; 34
35 // Display the value in myValue.
36 System.out.println("Now the value is " + myValue);
37 }
38 }
Program Output
number is 99
I am changing the value.
Now the value is 0

14. Code Listing 5-7 (PassString.java)
1 /**
2 This program demonstrates that String arguments
3 cannot be changed.
4 */ 5
6 public class PassString
7 {
8 public static void main(String[] args)
9 {
10 // Create a String object containing "Shakespeare".
// The name variable references the object.
12 String name = "Shakespeare"; 13
14 // Display the String referenced by the name variable.
15 System.out.println("In main, the name is " +
name); 17
18 // Call the changeName method, passing the
// contents of the name variable as an argument.
20 changeName(name); 21
(Continued)

15. Program Output In main, the name is Shakespeare
22 // Display the String referenced by the name variable.
23 System.out.println("Back in main, the name is " +
name);
25 } // END MAIN 26
27 /**
28 The changeName method accepts a String as its argument
29 and assigns the str parameter to a new String.
30 */ 31
32 public static void changeName( String str )
33 {
34 // Create a String object containing "Dickens".
// Assign its address to the str parameter variable.
36 str = "Dickens"; 37
38 // Display the String referenced by str.
39 System.out.println("In changeName, the name " +
"is now " + str);
41 }
42 }
Program Output
In main, the name is Shakespeare
In changeName, the name is now Dickens
Back in main, the name is Shakespeare

16. Code Listing 5-8 (LocalVars.java)
1 /**
2 This program demonstrates that two methods may have
3 local variables with the same name.
4 */ 5
6 public class LocalVars
7 {
8 public static void main(String[] args)
9 {
10 texas();
11 california();
12 } 13
14 /**
15 The texas method has a local variable named birds.
16 */ 17
18 public static void texas()
19 {
20 int birds = 5000; 21
(Continued)

17. In texas there are 5000 birds. In california there are 3500 birds.
22 System.out.println("In texas there are " +
birds + " birds.");
24 } // END TEXAS 25
26 /**
27 The california method also has a local variable named birds.
28 */
29 public static void california()
30 {
31 int birds = 3500; 32
33 System.out.println("In california there are " +
birds + " birds.");
35 }
36 } // END CLASs
Program Output
In texas there are 5000 birds.
In california there are 3500 birds.

18. Code Listing 5-9 (ValueReturn.java)
1 /**
2 This program demonstrates a value-returning method.
3 */ 4
5 public class ValueReturn
6 {
7 public static void main(String[] args)
8 {
9 int total, value1 = 20, value2 = 40; 10
11 // Call the sum method, passing the contents of
12 // value1 and value2 as arguments. Assign the
// return value to the total variable.
14 total = sum(value1, value2); 15
16 // Display the contents of all these variables.
17 System.out.println("The sum of " + value1 +
" and " + value2 + " is " +
total);
20 } 21
(Continued)

19. Program Output The sum of 20 and 40 is 60 22 /**
22 /**
23 The sum method returns the sum of its two parameters.
24 @param num1 The first number to be added.
25 @param num2 The second number to be added.
26 @return The sum of num1 and num2.
27 */ 28
29 public static int sum( int num1, int num2 )
30 {
31 int result; 32
33 // Assign the value of num1 + num2 to result.
34 result = num1 + num2; 35
36 // Return the value in the result variable.
37 return result;
38 }
39 }
Program Output
The sum of 20 and 40 is 60

20. Code Listing 5-10 (CupConverter.java)
1 import javax.swing.JOptionPane; 2
3 /**
4 This program converts cups to fluid ounces.
5 */ 6
7 public class CupConverter
8 {
9 public static void main(String[] args)
10 {
11 double cups; // To hold the number of cups
12 double ounces; // To hold the number of ounces 13 14
15 cups = getCups(); 16 17
18 ounces = cupsToOunces( cups ); 19 20
21 displayResults( cups, ounces );
System.exit(0);
23 } // End main
(Continued)

21. 24
25 /**
26 The getCups method prompts the user to enter a number
27 of cups.
28 @return The number of cups entered by the user.
29 */ 30
31 public static double getCups()
32 {
33 String input; // To hold input.
34 double numCups; // To hold cups. 35
36 // Get the number of cups from the user.
37 input = JOptionPane.showInputDialog(
38 "This program converts measurements\n" +
39 "in cups to fluid ounces. For your\n" +
40 "reference the formula is:\n" +
41 " 1 cup = 8 fluid ounces\n\n" +
42 "Enter the number of cups."); 43
44 // Convert the input to a double.
45 numCups = Double.parseDouble(input);
(Continued)

22. return numCups; 47 // Return the number of cups. 49 } // End GetCups50
51 /**
52 The cupsToOunces method converts a number of
53 cups to fluid ounces, using the formula
cup = 8 fluid ounces.
55 @param numCups The number of cups to convert.
56 @return The number of ounces.
57 */ 58
59 public static double cupsToOunces( double numCups )
60 {
61 return numCups * 8.0;
62 } 63
64 /**
65 The displayResults method displays a message showing
66 the results of the conversion.
(Continued)

23. 67 @param cups A number of cups.
68 @param ounces A number of ounces.
69 */ 70
71 public static void displayResults( double cups, double ounces )
72 {
73 // Display the number of ounces.
74 JOptionPane.showMessageDialog(null,
75 cups + " cups equals " +
76 ounces + " fluid ounces.");
77 }
78 }

24. Code Listing 5-11 (ReturnString.java)
1 /**
2 This program demonstrates a method that
3 returns a reference to a String object.
4 */ 5
6 public class ReturnString
7 {
8 public static void main(String[] args)
9 {
10 String customerName; 11
12 customerName = fullName( "John", "Martin“ );
13 System.out.println(customerName);
14 } 15
(Continued)

25. Program Output John Martin 16 /**
16 /**
17 The fullName method accepts two String arguments
18 containing a first and last name. It concatenates
19 them into a single String object.
20 @param first The first name.
21 @param last The last name.
22 @return A reference to a String object containing
23 the first and last names.
24 */ 25
26 public static String fullName( String first, String last )
27 {
28 String name; 29
30 name = first + " " + last;
31 return name;
32 }
33 }
Program Output
John Martin

26. filename = getFileName();
Code Listing 5-12 (SalesReport.java)
1 import java.util.Scanner; // For the Scanner class
2 import java.io.*; // For file I/O classes
3 import java.text.DecimalFormat; // For the DecimalFormat class
4 import javax.swing.JOptionPane; // For the JOptionPane class 5
6 /**
7 This program opens a file containing the sales
8 amounts for 30 days. It calculates and displays
9 the total sales and average daily sales.
10 */ 11
12 public class SalesReport
13 {
14 public static void main(String[] args) throws IOException
15 {
16 final int NUM_DAYS = 30; // Number of days of sales
17 String filename; // The name of the file to open
18 double totalSales; // Total sales for period
19 double averageSales; // Average daily sales 20
// Get the name of the file.
filename = getFileName();
(Continued)

27. 23
// Get the total sales from the file.
25 totalSales = getTotalSales(filename); 26
// Calculate the average.
28 averageSales = totalSales / NUM_DAYS; 29
// Display the total and average.
31 displayResults( totalSales, averageSales ); 32
33 System.exit(0);
34 } // End Main 35
36 /**
37 The getFileName method prompts the user to enter
38 the name of the file to open.
39 @return A reference to a String object containing
the name of the file.
41 */ 42
43 public static String getFileName()
44 {
(Continued)

28. 45 String file; 46
47 // Prompt the user to enter a file name.
48 file = JOptionPane.showInputDialog("Enter " +
"the name of the file\n" +
"containing 30 days of " +
"sales amounts."); 52
53 // Return the name.
54 return file;
55 } 56
57 /**
58 The getTotalSales method opens a file and
59 reads the daily sales amounts, accumulating
60 the total. The total is returned.
61 @param filename The name of the file to open.
62 @return The total of the sales amounts.
63 */ 64
65 public static double getTotalSales( String filename ) throwIOException

29. 67 {
68 double total = 0.0; // Accumulator
69 double sales; // A daily sales amount 70
// Open the file.
72 File file = new File(filename);
73 Scanner inputFile = new Scanner(file); 74
75 // This loop processes the lines read from the file,
// until the end of the file is encountered.
77 while ( inputFile.hasNext() )
78 {
79 // Read a double from the file.
80 sales = inputFile.nextDouble(); 81
82 // Add sales to the value already in total.
83 total += sales;
84 } 85
// Close the file.
87 inputFile.close(); 88
(Continued)

30. 89 // Return the total sales.
90 return total;
91 } // END getTotalSales 92
93 /**
94 The displayResults method displays the total and
95 average daily sales.
96 @param total The total sales.
97 @param avg The average daily sales.
98 */ 99
100 public static void displayResults( double total, double avg )
101 {
102 // Create a DecimalFormat object capable of formatting
103 // a dollar amount.
104 DecimalFormat dollar = new DecimalFormat("#,###.00");
105
106 // Display the total and average sales.
107 JOptionPane.showMessageDialog(null, "The total sales for " +
"the period is $" + dollar.format(total) +
"\nThe average daily sales were $" +
dollar.format(avg));
111 }
112 }