Java程序辅导

5Control
Statements: Part 2
OB J ECT IVES
In this chapter you will learn:
■ The essentials of counter-controlled repetition.
■ To use the for and do…while repetition statements to execute
statements in a program repeatedly.
■ To understand multiple selection using the switch selection
statement.
■ To use the break and continue program control statements to
alter the flow of control.
■ To use the logical operators to form complex conditional
expressions in control statements.
Not everything that can be
counted counts, and not
every thing that counts can
be counted.
—Albert Einstein
Who can control his fate?
—William Shakespeare
The used key is always bright.
—Benjamin Franklin
Intelligence … is the faculty
of making artificial objects,
especially tools to make tools.
—Henri Bergson
Every advantage in the past
is judged in the light of the
final issue.
—Demosthenes
Chapter 5 Control Statements: Part 2 153
Name: Date:
Section:
Assignment Checklist
Exercises Assigned: Circle assignments Date Due
Prelab Activities
Matching YES NO
Fill in the Blank 13, 14, 15, 16, 17, 18, 19, 20, 21
Short Answer 22, 23, 24, 25, 26
Programming Output 27, 28, 29, 30, 31, 32, 33, 34, 35,
36
Correct the Code 37, 38, 39, 40
Lab Exercises
Exercise 1 — Triangles YES NO
Follow-Up Question and Activity 1
Exercise 2 — Sales YES NO
Follow-Up Questions and Activities 1, 2
Exercise 3 — Pythagorean Triples YES NO
Follow-Up Questions and Activities 1, 2, 3
Debugging YES NO
Postlab Activities
Coding Exercises 1, 2, 3, 4, 5, 6, 7, 8
Programming Challenges 1, 2
Chapter 5 Control Statements: Part 2 155
Prelab Activities
Name: Date:
Section:
Matching
After reading Chapter 5 of Java How to Program: Seventh Edition, answer the given questions. These questions
are intended to test and reinforce your understanding of key Java concepts. You may answer these questions ei-
ther before or during the lab.
For each term in the left column, write the letter for the description that best matches the term from the right
column.
Term Description
E
H
J
A
B
F
D
L
I
G
C
K
1. &&
2. ||
3. !
4. switch
5. continue
6. break
7. for repetition statement
8. do…while repetition statement
9. |
10. off-by-one error
11. &
12. constant
a) Handles a series of decisions, in which a particular
variable or expression is tested for values it can as-
sume and different actions are taken.
b) Skips any remaining statements in the body of a rep-
etition statement and proceeds with the next itera-
tion of the loop.
c) Boolean logical AND
d) Handles all of the details of counter-controlled rep-
etition.
e) Conditional AND.
f) Causes immediate exit from a repetition statement.
g) Can be caused by the use of an incorrect relational
operator or using an incorrect final value of a loop
counter in the condition of a repetition statement.
h) Conditional OR.
i) Boolean logical inclusive OR.
j) Logical negation.
k) A variable which contains a value which does not
change for the entire program.
l) Repetition statement that tests the loop-continua-
tion condition at the end of the loop, so that the
body of the loop will execute at least once.
Prelab Activities Name:
Fill in the Blank
Chapter 5 Control Statements: Part 2 157
Name: Date:
Section:
Fill in the Blank
Fill in the blanks for each of the following statements:
13. The %b format specifier causes the value of a boolean expression to be output as the word true or the
word false based on the expression’s value.
14. Typically, for statements are used for counter-controlled repetition and while statements are used
for sentinel-controlled repetition.
15. In most programs, it is necessary to include a(n) break statement after the statements for each case in a
switch statement.
16. The scope of a variable defines where it can be referenced in a program by using just the variable’s name.
17. Logical operators may be used to form complex conditions by combining conditions.
18. Placing a semicolon after the header of a for statement is normally a(n) logic error.
19. Programs should control counting loops with integer values.
20. Infinite loops occur when the loop-continuation condition in a repetition statement never becomes
false .
21. The expression in parentheses following keyword switch is called the controlling expression of the
switch .
Prelab Activities Name:
Short Answer
Chapter 5 Control Statements: Part 2 159
Name: Date:
Section:
Short Answer
Answer the following questions in the space provided. Your answers should be concise; aim for two or three sen-
tences.
22. What is required to perform counter-controlled repetition?
Counter-controlled repetition requires the name of a control variable, the initial value of the control variable, the
increment or decrement by which the control variable is modified each time through the loop, and the condition
that tests for the final value of the control variable.
23. Why should programs control counting loops with integers and not with floating-point numbers?
Programs should control counting loops with integers because floating-point values may be approximate. Count-
ing with floating-point values may result in imprecise counter values and inaccurate tests for termination.
24. Explain why placing a semicolon after the header of a for statement is a logic error and not a compilation
error.
Placing a semicolon after the for statement header is not a compilation error because Java treats the semicolon
as an empty statement, which satisfies the requirement that the for statement have at least one statement in its
body. This normally is a logic error because the code will compile, but will not execute correctly.
25. Differentiate between the while and the do…while repetition statements.
In a while statement the program tests the loop-continuation condition at the beginning of the loop, before per-
forming the body of the loop. If the initial condition is false, the body does not execute. The do…while state-
ment tests the condition after performing the body of the loop, so the body of the loop always executes at least
once.
26. Explain why an infinite loop can occur and how one can be prevented.
An infinite loop occurs in a repetition statement when the loop-continuation condition never becomes false.
In a counter-controlled loop, ensure that the control variable value is modified in a way that will eventually cause
the loop-continuation condition to become false. In a sentinel-controlled loop ensure that the sentinel value is
eventually input.
Prelab Activities Name:
Programming Output
Chapter 5 Control Statements: Part 2 161
Name: Date:
Section:
Programming Output
For each of the given program segments, read the code and write the output in the space provided below each
program. [Note: Do not execute these programs on a computer.]
For the following questions, assume that the code segments are contained within the main method of a Java ap-
plication.
For questions 27–30, use the following code segment:
27. What will be the output if the following code is placed at line 4 of the preceding code?
Your answer:
28. What will be the output if the following code is placed at line 4 of the preceding code?
Your answer:
1 int startingValue;
2 int terminatingValue;
3 int stepValue;
4
5 for ( int i = startingValue; i < terminatingValue; i += stepValue )
6 System.out.printf( "%d ", i );
1 startingValue = 0;
2 terminatingValue = 5;
3 stepValue = 1;
0 1 2 3 4
1 startingValue = -3;
2 terminatingValue = 2;
3 stepValue = 1;
-3 -2 -1 0 1
Prelab Activities Name:
Programming Output
162 Control Statements: Part 2 Chapter5
29. What will be the output if the following code is placed at line 4 of the preceding code?
Your answer:
No Output
30. What will be the output if the following code is placed at line 4 of the preceding code?
Your answer:
For questions 31–35, use the following class definition:
1 startingValue = 6;
2 terminatingValue = 5;
3 stepValue = 1;
1 startingValue = 0;
2 terminatingValue = 5;
3 stepValue = 3;
0 3
1 int startingValue;
2 int terminatingValue;
3 int stepValue;
4
5 for ( int i = startingValue; i <= terminatingValue; i += stepValue )
6 {
7 switch( i )
8 {
9 case 0:
10 System.out.print( "Hello there, " );
11 break;
12 case 1:
13 System.out.println( "What’s up? " );
14 break;
15 case 2:
16 System.out.println( "How are you doing? " );
17 break;
18 case 3:
19 System.out.println( "Terrific. " );
20 break;
21 case 4:
22 System.out.println( "Beautiful day isn't it? " );
23 break;
24 case 5:
25 System.out.println( "Yes it is. " );
26 break;
27 default:
28 System.out.println( "See you later. " );
29 } // end switch
30 } // end for
Prelab Activities Name:
Programming Output
Chapter 5 Control Statements: Part 2 163
31. What will be the output if the following code is placed at line 4 of the preceding class definition?
Your answer:
32. What will be the output if the following code is placed at line 4 of the preceding code?
Your answer:
33. What will be the output if the following code is placed at line 4 of the preceding code?
Your answer:
1 startingValue = 0;
2 terminatingValue = 6;
3 stepValue = 2;
Hello there, How are you doing?
Beautiful day isn’t it?
See you later.
1 startingValue = 0;
2 terminatingValue = 6;
3 stepValue = 3;
Hello there, Terrific.
See you later.
1 startingValue = -3;
2 terminatingValue = 2;
3 stepValue = 1;
See you later.
See you later.
See you later.
Hello there, What’s up?
How are you doing?
Prelab Activities Name:
Programming Output
164 Control Statements: Part 2 Chapter5
34. What will be the output if the following code is placed at line 4 of the preceding code?
Your answer:
35. What will be the output if the following code is placed at line 4 of the preceding code?
Your answer:
No Output
36. What is output by the following code segment?
Your answer:
1 startingValue = -5;
2 terminatingValue = 1;
3 stepValue = 2;
See you later.
See you later.
See you later.
What’s up?
1 startingValue = 10;
2 terminatingValue = 5;
3 stepValue = 1;
1 for ( int i = 0; i <= 11; i++ )
2 {
3 if ( i % 2 == 0 )
4 continue;
5
6 if ( i == 11 )
7 break;
8
9 System.out.printf( "%d ", i );
10 } // end for
1 3 5 7 9
Prelab Activities Name:
Correct the Code
Chapter 5 Control Statements: Part 2 165
Name: Date:
Section:
Correct the Code
Determine if there is an error in each of the following program segments. If there is an error, specify whether it
is a logic error or a compilation error, circle the error in the program and write the corrected code in the space
provided after each problem. If the code does not contain an error, write “no error.” [Note: There may be more
than one error in each program segment.]
37. The following for loop should calculate the product of the integers in the range 1–5.
Your answer:
• Variable product must be initialized outside of the for loop (line 1). Logic error.
38. The following for loop should print the sum of consecutive odd and even integers in the range 1–10. The
expected output is shown below the code.
1 for ( int i = 1; i <= 5; i++ )
2 {
3 int product = 1;
4 product *= i;
5 }
1
2
3 for ( int i = 1; i <= 5; i++ )
4 product *= i;
1 for ( int i = 1, j = 1; i <= 10 && j <= 10; i++, j++)
2 System.out.printf( "%d + %d = %d\n", i, j, ( i + j ) );
1 + 2 = 3
3 + 4 = 7
5 + 6 = 11
7 + 8 = 15
9 + 10 = 19
int product = 1;
Prelab Activities Name:
Correct the Code
166 Control Statements: Part 2 Chapter5
Your answer:
• On line 1, variable j should be initialized to 2 and both i and j should be incremented by 2 after each
iteration. Logic error.
39. The following for loop should loop 10 times and compute the product of i times 2 plus 1 in each iteration.
For example, if the loop counter is 4, the program should print 4 * 2 + 1 = 9.
Your answer:
• The preincrement operator on line 2 cannot be used because the expression in parentheses cannot be
modified. The line should use a simple addition statement. Compilation error.
40. The following switch statement should print either "x is 5", "x is 10" or "x is neither 5 nor 10".
Your answer:
No Error
1 for ( int i = 1, j = ; i <= 10 && j <= 10; )
2 System.out.printf( "%d + %d = %d\n", i, j, ( i + j ) );
1 for ( int i = 1; i <= 10; i++ )
2 System.out.printf( "%d * 2 + 1 = %d", i, ( ++( i * 2 ) ) );
3
1 for ( int i = 1; i <= 10; i++ )
2 System.out.printf( "%d * 2 + 1 = %d", i, ( i * 2 ) + 1 );
3
1 switch ( x )
2 {
3 case 5:
4 System.out.println( "x is 5" );
5 break;
6 case 10:
7 System.out.println( "x is 10" );
8 break;
9 default:
10 System.out.println( "x is neither 5 nor 10" );
11 break;
12 } // end switch
2 i+=2, j+=2
Chapter 5 Control Statements: Part 2 167
Lab Exercises
Name: Date:
Section:
Lab Exercise 1 — Triangles
The following problem is intended to be solved in a closed-lab session with a teaching assistant or instructor
present. The problem is divided into six parts:
1. Lab Objectives
2. Problem Description
3. Sample Output
4. Program Template (Fig. L 5.1 and Fig. L 5.2)
5. Problem-Solving Tips
6. Follow-Up Question and Activity
The program template represents a complete working Java program with one or more key lines of code replaced
with comments. Read the problem description and examine the output, then study the template code. Using the
problem-solving tips as a guide, replace the /* */ comments with Java code. Compile and execute the program.
Compare your output with the sample output provided. Then answer the follow-up question. The source code
for the template is available at www.deitel.com/books/jhtp7/ and www.prenhall.com/deitel.
Lab Objectives
This lab was designed to reinforce programming concepts from Chapter 5 of Java How To Program: Seventh Edi-
tion. In this lab, you will practice:
• Nested for loops.
• Using counter-controlled repetition.
The follow-up question and activity also will give you practice in:
• Using techniques from one program to perform a similar task in another program.
Problem Description
Write an application that displays the following patterns separately, one below the other. Use for loops to gen-
erate the patterns. All asterisks (*) should be printed by a single statement of the form
System.out.print( "*" ); which causes the asterisks to print side by side. A statement of the form Sys-
tem.out.println(); can be used to move to the next line. A statement of the form System.out.print( " " );
can be used to display a space for the last two patterns. There should be no other output statements in the pro-
gram.
Lab Exercises Name:
Lab Exercise 1 — Triangles
168 Control Statements: Part 2 Chapter5
Sample Output
Template
*
**
***
****
*****
******
*******
********
*********
**********
**********
*********
********
*******
******
*****
****
***
**
*
**********
*********
********
*******
******
*****
****
***
**
*
*
**
***
****
*****
******
*******
********
*********
**********
1 // Lab 1: Triangles.java
2 // Program prints four triangles, one below the other
3 public class Triangles
4 {
Fig. L 5.1 | Triangles.java. (Part 1 of 2.)
Lab Exercises Name:
Lab Exercise 1 — Triangles
Chapter 5 Control Statements: Part 2 169
Problem-Solving Tips
1. For the first triangle use a nested for statement in which the outer loop counts rows and the inner loop
counts columns. The inner loop for the first triangle should count from 1 to the current row number.
2. For the second triangle use a nested for statement in which the outer loop counts backward from 10 to
1. The inner loop should be identical to the one used for the first triangle.
3. The last two patterns require that each row begin with an appropriate number of blank spaces.
4. For the third and fourth triangles use two separate inner loops—one for displaying spaces and one for
displaying asterisks.
5. If you have any questions as you proceed, ask your lab instructor for assistance.
5 // draw four triangles
6 public void drawTriangles()
7 {
8 int row; // the row position
9 int column; // the column position
10 int space; // number of spaces to print
11
12 // first triangle
13 /* Write code to display the first triangle. Use nested for loops. The
14 outer loop should control which row of asterisks is being displayed.
15 The inner loop should display one asterisk at a time. */
16
17 // second triangle
18 /* Write code to display the second triangle using techniques similar to
19 the first triangle */
20
21 // third triangle
22 /* Write code to display the third triangle. The outer for loop should
23 contain two separate inner for loops--one to display spaces and one to
24 display asterisks. */
25
26 // fourth triangle
27 /* Write code to display the fourth triangle using techniques similar to
28 the third triangle. */
29 } // end method drawTriangles
30 } // end class Triangles
1 // Lab 1: TrianglesTest.java
2 // Test application for class Triangles
3 public class TrianglesTest
4 {
5 public static void main( String args[] )
6 {
7 Triangles application = new Triangles();
8 application.drawTriangles();
9 } // end main
10 } // end class TrianglesTest
Fig. L 5.2 | TrianglesTest.java
Fig. L 5.1 | Triangles.java. (Part 2 of 2.)
Lab Exercises Name:
Lab Exercise 1 — Triangles
170 Control Statements: Part 2 Chapter5
Solution
1 // Lab 1: Triangles.java
2 // Program prints four triangles, one below the other
3 public class Triangles
4 {
5 // draw four triangles
6 public void drawTriangles()
7 {
8 int row; // the row position
9 int column; // the column position
10 int space; // number of spaces to print
11
12 // first triangle
13 for ( row = 1; row <= 10; row++ )
14 {
15 for ( column = 1; column <= row; column++ )
16 System.out.print( "*" );
17
18 System.out.println();
19 } // end for loop
20
21 System.out.println();
22
23 // second triangle
24 for ( row = 10; row >= 1; row-- )
25 {
26 for ( column = 1; column <= row; column++ )
27 System.out.print( "*" );
28
29 System.out.println();
30 } // end for loop
31
32 System.out.println();
33
34 // third triangle
35 for ( row = 10; row >= 1; row-- )
36 {
37 for ( space = 10; space > row; space-- )
38 System.out.print( " " );
39
40 for ( column = 1; column <= row; column++ )
41 System.out.print( "*" );
42
43 System.out.println();
44 } // end for loop
45
46 System.out.println();
47
48 // fourth triangle
49 for ( row = 10; row >= 1; row-- ) {
50
51 for ( space = 1; space < row; space++ )
52 System.out.print( " " );
53
54 for ( column = 10; column >= row; column-- )
55 System.out.print( "*" );
56
Lab Exercises Name:
Lab Exercise 1 — Triangles
Chapter 5 Control Statements: Part 2 171
Follow-Up Question and Activity
1. Using the techniques of the third and fourth triangles in Lab Exercise 1, display two triangles in the format
shown below.
57 System.out.println();
58 } // end for loop
59 } // end method drawTriangles
60 } // end class Triangles
1 // Lab 1: TrianglesTest.java
2 // Test application for class Triangles
3 public class TrianglesTest
4 {
5 public static void main( String args[] )
6 {
7 Triangles application = new Triangles();
8 application.drawTriangles();
9 } // end main
10 } // end class TrianglesTest
*********
*******
*****
***
*
*
***
*****
*******
*********
1 // Lab 1: Triangles.java
2 // Program prints four triangles, one below the other
3 public class Triangles
4 {
5 // draw four triangles
6 public void drawTriangles()
7 {
8 int row; // the row position
9 int column; // the column position
10 int space; // number of spaces to print
11
12 // first triangle
13 for ( row = 0; row <= 4; row++ )
14 {
15 for ( column = row; column >= 0; column-- )
16 System.out.print( " " );
17
18 for ( column = 2 * row; column <= 8; column++ )
19 System.out.print( "*" );
20
Lab Exercises Name:
Lab Exercise 1 — Triangles
172 Control Statements: Part 2 Chapter5
21 System.out.println();
22 } // end for loop
23
24 // second triangle
25 for ( row = 0; row <= 4; row++ )
26 {
27 for ( column = row; column <= 4; column++ )
28 System.out.print( " " );
29
30 for ( column = 2 * row; column >= 0; column-- )
31 System.out.print( "*" );
32
33 System.out.println();
34 } // end for loop
35 } // end method drawTriangles
36 } // end class Triangles
1 // Lab 1: TrianglesTest.java
2 // Test application for class Triangles
3 public class TrianglesTest
4 {
5 public static void main( String args[] )
6 {
7 Triangles application = new Triangles();
8 application.drawTriangles();
9 } // end main
10 } // end class TrianglesTest
Lab Exercises Name:
Lab Exercise 2 — Sales
Chapter 5 Control Statements: Part 2 173
Name: Date:
Section:
Lab Exercise 2 — Sales
The following problem is intended to be solved in a closed-lab session with a teaching assistant or instructor
present. The problem is divided into six parts:
1. Lab Objectives
2. Problem Description
3. Sample Output
4. Program Template (Fig. L 5.3 and Fig. L 5.4)
5. Problem-Solving Tips
6. Follow-Up Questions and Activities
The program template represents a complete working Java program with one or more key lines of code replaced
with comments. Read the problem description and examine the output, then study the template code. Using the
problem-solving tips as a guide, replace the /* */ comments with Java code. Compile and execute the program.
Compare your output with the sample output provided. Then answer the follow-up questions. The source code
for the template is available at www.deitel.com/books/jhtp7/ and www.prenhall.com/deitel.
Lab Objectives
This lab was designed to reinforce programming concepts from Chapter 5 of Java How To Program: Seventh Edi-
tion. In this lab, you will practice:
• Using switch statements.
The follow-up questions and activities also will give you practice:
• Validating the input from the user.
• Extending an existing program.
Problem Description
Amail-order house sells five products whose retail prices are as follows: Product 1, $2.98; product 2, $4.50; prod-
uct 3, $9.98; product 4, $4.49 and product 5, $6.87. Write an application that reads a series of pairs of numbers
as follows:
a) product number
b) quantity sold
Your program should use a switch statement to determine the retail price for each product. It should calculate
and display the total retail value of all products sold. Use a sentinel-controlled loop to determine when the pro-
gram should stop looping and display the final results.
Lab Exercises Name:
Lab Exercise 2 — Sales
174 Control Statements: Part 2 Chapter5
Sample Output
Template
Enter product number (1-5) (0 to stop): 1
Enter quantity sold: 5
Enter product number (1-5) (0 to stop): 5
Enter quantity sold: 10
Enter product number (1-5) (0 to stop): 0
Product 1: $14.90
Product 2: $0.00
Product 3: $0.00
Product 4: $0.00
Product 5: $68.70
1 // Lab 2: Sales.java
2 // Program calculates sales, based on an input of product
3 // number and quantity sold
4 import java.util.Scanner;
5
6 public class Sales
7 {
8 // calculates sales for 5 products
9 public void calculateSales()
10 {
11 Scanner input = new Scanner( System.in );
12
13 double product1 = 0; // amount sold of first product
14 double product2 = 0; // amount sold of second product
15 double product3 = 0; // amount sold of third product
16 double product4 = 0; // amount sold of fourth product
17 double product5 = 0; // amount sold of fifth product
18
19 /* Ask the user to enter product number */
20
21 /* Create while statement that loops until sentinel is entered */
22
23 /* Determine whether user’s product number is in 1-5 */
24
25 /* If so, ask user to input the quantity sold */
26
27 /* Write a switch statement here that will compute the total
28 for that product */
29
30 /* If product number is not in 1-5, test if product number is not 0 */
31 /* Display error message for invalid product number */
32
33 /* Ask the user to enter another product number */
34
35 /* end while loop */
36
37 // print summary
38 System.out.println();
39 System.out.printf( "Product 1: $%.2f\n", product1 );
Fig. L 5.3 | Sales.java. (Part 1 of 2.)
Lab Exercises Name:
Lab Exercise 2 — Sales
Chapter 5 Control Statements: Part 2 175
Problem-Solving Tips
1. Before your while loop, request the first product number from the user.
2. Use a sentinel value to control the loop. This loop should terminate when the product number entered
is zero.
3. If the user provides a valid product number, inside the loop, request a quantity for that product. Then,
perform the appropriate calculation in the switch statement.
4. Your switch statement should consist of five cases, each setting the correct dollar value, depending on
the quantity that the user entered.
5. Inside the closing right brace (}) of the loop’s body, request the next product number from the user.
6. Be sure to follow the spacing and indentation conventions mentioned in the text. Before and after each
control statement, place a line of vertical space to make the code more readable.
7. If you have any questions as you proceed, ask your lab instructor for assistance.
Solution
40 /* write code here for the rest of the summary message it should contain
41 the totals for the rest of the products, each on it’s own line */
42 } // end method calculateSales
43 } // end class Sales
1 // Lab 2: SalesTest.java
2 // Test application for class Sales
3 public class SalesTest
4 {
5 public static void main( String args[] )
6 {
7 Sales application = new Sales();
8 application.calculateSales();
9 } // end main
10 } // end class SalesTest
Fig. L 5.4 | SalesTest.java
1 // Lab 2: Sales.java
2 // Program calculates sales, based on an input of product
3 // number and quantity sold
4 import java.util.Scanner;
5
6 public class Sales
7 {
8 // calculates sales for 5 products
9 public void calculateSales()
10 {
11 Scanner input = new Scanner( System.in );
12
13 double product1 = 0; // amount sold of first product
14 double product2 = 0; // amount sold of second product
15 double product3 = 0; // amount sold of third product
Fig. L 5.3 | Sales.java. (Part 2 of 2.)
Lab Exercises Name:
Lab Exercise 2 — Sales
176 Control Statements: Part 2 Chapter5
16 double product4 = 0; // amount sold of fourth product
17 double product5 = 0; // amount sold of fifth product
18
19 System.out.print( "Enter product number (1-5) (0 to stop): " );
20 int productId = input.nextInt();
21
22 // ask user for product number until flag value entered
23 while ( productId != 0 )
24 {
25 if ( productId >= 1 && productId <= 5 )
26 {
27 // determine the number sold of the item
28 System.out.print( "Enter quantity sold: " );
29 int quantity = input.nextInt();
30
31 // increment the total for the item by the
32 // price times the quantity sold
33 switch ( productId )
34 {
35 case 1:
36 product1 += quantity * 2.98;
37 break;
38
39 case 2:
40 product2 += quantity * 4.50;
41 break;
42
43 case 3:
44 product3 += quantity * 9.98;
45 break;
46
47 case 4:
48 product4 += quantity * 4.49;
49 break;
50
51 case 5:
52 product5 += quantity * 6.87;
53 break;
54 } // end switch
55 } // end if
56 else if ( productId != 0 )
57 System.out.println(
58 "Product number must be between 1 and 5 or 0 to stop" );
59
60 System.out.print( "Enter product number (1-5) (0 to stop): " );
61 productId = input.nextInt();
62 } // end while loop
63
64 // print summary
65 System.out.println();
66 System.out.printf( "Product 1: $%.2f\n", product1 );
67 System.out.printf( "Product 2: $%.2f\n", product2 );
68 System.out.printf( "Product 3: $%.2f\n", product3 );
69 System.out.printf( "Product 4: $%.2f\n", product4 );
70 System.out.printf( "Product 5: $%.2f\n", product5 );
71 } // end method calculateSales
72 } // end class Sales
Lab Exercises Name:
Lab Exercise 2 — Sales
Chapter 5 Control Statements: Part 2 177
Follow-Up Questions and Activities
1. What happens when the user inputs a number that is other than 1 through 5 or 0? Why? What is the output
when the user enters a number like 7?
In the original program, if the user enters a number other than 1-5 or 0, a message appears that informs
the user to enter a valid number. This is because of the while loop that runs until a valid number has been
entered.
2. Modify the program so that there is a sixth product, priced at $20.00, that represents a package of all the
products. For each of the packages purchased, add $4.00 to the totals for all the other products. Do not keep
track of the packages separately.
1 // Lab 2: SalesTest.java
2 // Test application for class Sales
3 public class SalesTest
4 {
5 public static void main( String args[] )
6 {
7 Sales application = new Sales();
8 application.calculateSales();
9 } // end main
10 } // end class SalesTest
1 // Lab 2: Sales.java
2 // Program calculates sales, based on an input of product
3 // number and quantity sold
4 import java.util.Scanner;
5
6 public class Sales
7 {
8 // calculates sales for 5 products
9 public void calculateSales()
10 {
11 Scanner input = new Scanner( System.in );
12
13 double product1 = 0; // amount sold of first product
14 double product2 = 0; // amount sold of second product
15 double product3 = 0; // amount sold of third product
16 double product4 = 0; // amount sold of fourth product
17 double product5 = 0; // amount sold of fifth product
18
19 System.out.print( "Enter product number (1-6) (0 to stop): " );
20 int productId = input.nextInt();
21
22 // ask user for product number until flag value entered
23 while ( productId != 0 )
24 {
25 if ( productId >= 1 && productId <= 6 )
26 {
27 // determine the number sold of the item
28 System.out.print( "Enter quantity sold: " );
29 int quantity = input.nextInt();
30
Lab Exercises Name:
Lab Exercise 2 — Sales
178 Control Statements: Part 2 Chapter5
31 // increment the total for the item by the
32 // price times the quantity sold
33 switch ( productId )
34 {
35 case 1:
36 product1 += quantity * 2.98;
37 break;
38
39 case 2:
40 product2 += quantity * 4.50;
41 break;
42
43 case 3:
44 product3 += quantity * 9.98;
45 break;
46
47 case 4:
48 product4 += quantity * 4.49;
49 break;
50
51 case 5:
52 product5 += quantity * 6.87;
53 break;
54
55 case 6:
56 product1 += quantity * 4;
57 product2 += quantity * 4;
58 product3 += quantity * 4;
59 product4 += quantity * 4;
60 product5 += quantity * 4;
61 break;
62 } // end switch
63 } // end if
64 else if ( productId != 0 )
65 System.out.println(
66 "Product number must be between 1 and 6 or 0 to stop" );
67
68 System.out.print( "Enter product number (1-6) (0 to stop): " );
69 productId = input.nextInt();
70 } // end while loop
71
72 // print summary
73 System.out.println();
74 System.out.printf( "Product 1: $%.2f\n", product1 );
75 System.out.printf( "Product 2: $%.2f\n", product2 );
76 System.out.printf( "Product 3: $%.2f\n", product3 );
77 System.out.printf( "Product 4: $%.2f\n", product4 );
78 System.out.printf( "Product 5: $%.2f\n", product5 );
79 } // end method calculateSales
80 } // end class Sales
Lab Exercises Name:
Lab Exercise 2 — Sales
Chapter 5 Control Statements: Part 2 179
1 // Lab 2: SalesTest.java
2 // Test application for class Sales
3 public class SalesTest
4 {
5 public static void main( String args[] )
6 {
7 Sales application = new Sales();
8 application.calculateSales();
9 } // end main
10 } // end class SalesTest
Enter product number (1-6) (0 to stop): 1
Enter quantity sold: 5
Enter product number (1-6) (0 to stop): 5
Enter quantity sold: 10
Enter product number (1-6) (0 to stop): 6
Enter quantity sold: 2
Enter product number (1-6) (0 to stop): 0
Product 1: $22.90
Product 2: $8.00
Product 3: $8.00
Product 4: $8.00
Product 5: $76.70
Lab Exercises Name:
Lab Exercise 3 — Pythagorean Triples
Chapter 5 Control Statements: Part 2 181
Name: Date:
Section:
Lab Exercise 3 — Pythagorean Triples
The following problem is intended to be solved in a closed-lab session with a teaching assistant or instructor
present. The problem is divided into six parts:
1. Lab Objectives
2. Problem Description
3. Sample Output
4. Program Template (Fig. L 5.5)
5. Problem-Solving Tips
6. Follow-Up Questions and Activities
The program template represents a complete working Java program with one or more key lines of code replaced
with comments. Read the problem description and examine the output, then study the template code. Using the
problem-solving tips as a guide, replace the /* */ comments with Java code. Compile and execute the program.
Compare your output with the sample output provided. Then answer the follow-up questions. The source code
for the template is available at www.deitel.com/books/jhtp7/ and www.prenhall.com/deitel.
Lab Objectives
This lab was designed to reinforce programming concepts from Chapter 5 of Java How To Program: Seventh Edi-
tion. In this lab, you will practice:
• Nested for loops.
• Using counter-controlled repetition.
• Using “brute force” techniques to solve a problem.
The follow-up questions and activities will also give you practice:
• Using break statements.
• Using continue statements.
• Using counters to determine the number of iterations a loop performs.
Problem Description
A right triangle can have sides whose lengths are all integers. The set of three integer values for the lengths of the
sides of a right triangle is called a Pythagorean triple. The lengths of the three sides must satisfy the relationship
that the sum of the squares of two of the sides is equal to the square of the hypotenuse. Write an application to
find all Pythagorean triples for side1, side2 and the hypotenuse, all no larger than 500. Use a triple-nested for
loop that tries all possibilities. This method is an example of “brute-force” computing. You will learn in more
advanced computer science courses that there are large numbers of interesting problems for which there is no
known algorithmic approach other than using sheer brute force.
Lab Exercises Name:
Lab Exercise 3 — Pythagorean Triples
182 Control Statements: Part 2 Chapter5
Sample Output
Template
Solution
s1: 3, s2: 4, h: 5
s1: 4, s2: 3, h: 5
s1: 5, s2: 12, h: 13
s1: 6, s2: 8, h: 10
s1: 7, s2: 24, h: 25
.
.
.
s1: 480, s2: 31, h: 481
s1: 480, s2: 88, h: 488
s1: 480, s2: 108, h: 492
s1: 480, s2: 140, h: 500
s1: 483, s2: 44, h: 485
1 // Lab 3: Triples.java
2 // Program calculates Pythagorean triples
3 public class Triples
4 {
5 public static void main( String args[] )
6 {
7 // declare the three sides of a triangle
8 int side1;
9 int side2;
10 int hypotenuse;
11
12 /* Write loop for side1 to try the values 1-500. */
13
14 /* Write loop for side2 to try the values 1-500. */
15
16 /* Write loop for hypotenuse to try the values 1-500 */
17
18 /* Write an if statement that determines whether the sum of the
19 two sides squared equals the hypotenuse squared. If this
20 condition is true display side1, side2 and hypotenuse. */
21 } // end main
22 } // end class Triples
Fig. L 5.5 | Triples.java.
1 // Lab 3: Triples.java
2 // Program calculates Pythagorean triples
3 public class Triples
4 {
5 public static void main( String args[] )
6 {
7 // declare the three sides of a triangle
8 int side1;
Lab Exercises Name:
Lab Exercise 3 — Pythagorean Triples
Chapter 5 Control Statements: Part 2 183
Problem-Solving Tips
1. This program does not require any input from the user.
2. The formula for the Pythagorean Theorem is hypotenuse
2
= side1
2
+ side2
2
.
3. Do not be concerned about trying values that do not make sense, such as a 1-500-1 triangle. Brute-force
computing techniques try all possible values.
4. Use an if statement to determine whether the sum of the two squared sides is equal to the hypotenuse
squared. If so, output side1, side2 and hypotenuse.
5. If you have any questions as you proceed, ask your lab instructor for assistance.
Follow-Up Questions and Activities
1. How many times did this program execute the innermost for loop? Add another counter to the program
that counts the number of times the inner loop iterates. Before exiting the program, display the counter val-
ue.
9 int side2;
10 int hypotenuse;
11
12 for ( side1 = 1; side1 <= 500; side1++ )
13
14 for ( side2 = 1; side2 <= 500; side2++ )
15
16 for ( hypotenuse = 1; hypotenuse <= 500; hypotenuse++ )
17
18 // use Pythagorean Theorem to print right triangles
19 if ( ( side1 * side1 ) + ( side2 * side2 ) ==
20 ( hypotenuse * hypotenuse ) )
21 System.out.printf( "s1: %d, s2: %d, h: %d\n",
22 side1, side2, hypotenuse );
23 } // end main
24 } // end class Triples
1 // Lab 3: Triples.java
2 // Program calculates Pythagorean triples
3 public class Triples
4 {
5 public static void main( String args[] )
6 {
7 // declare the three sides of a triangle
8 int side1;
9 int side2;
10 int hypotenuse;
11 int counter = 0;
12
13 for ( side1 = 1; side1 <= 500; side1++ )
14
15 for ( side2 = 1; side2 <= 500; side2++ )
16
17 for ( hypotenuse = 1; hypotenuse <= 500; hypotenuse++ )
18 {
19 counter++;
20
Lab Exercises Name:
Lab Exercise 3 — Pythagorean Triples
184 Control Statements: Part 2 Chapter5
2. Add a break statement to the program inside the innermost for loop. This break statement should execute
after the twentieth Pythagorean triple is found. Explain what happens to the program after the 20th triple
is found. Do all three for loops exit, or just the innermost one? What happens differently when the break
statement is placed inside the second loop? What happens differently when the break statement is placed
inside the outermost loop? [Hint: Use the loop counter you defined in the previous follow-up question to
count how many times the loops execute.]
Break in innermost for loop:
21 // use Pythagorean Theorem to print right triangles
22 if ( ( side1 * side1 ) + ( side2 * side2 ) ==
23 ( hypotenuse * hypotenuse ) )
24 System.out.printf( "s1: %d, s2: %d, h: %d\n",
25 side1, side2, hypotenuse );
26 } // end for
27
28 System.out.printf( "The inner loop iterated %d times.\n", counter );
29 } // end main
30 } // end class Triples
s1: 3, s2: 4, h: 5
s1: 4, s2: 3, h: 5
s1: 5, s2: 12, h: 13
s1: 6, s2: 8, h: 10
s1: 7, s2: 24, h: 25
.
.
.
s1: 480, s2: 31, h: 481
s1: 480, s2: 88, h: 488
s1: 480, s2: 108, h: 492
s1: 480, s2: 140, h: 500
s1: 483, s2: 44, h: 485
The inner loop iterated 125000000 times.
1 // Lab 3: Triples1.java
2 // Program calculates Pythagorean triples
3 public class Triples1
4 {
5 public static void main( String args[] )
6 {
7 // declare the three sides of a triangle
8 int side1;
9 int side2;
10 int hypotenuse;
11 int counter = 0;
12 int numberOfTriples = 0;
13
14 for ( side1 = 1; side1 <= 500; side1++ )
15
16 for ( side2 = 1; side2 <= 500; side2++ )
17
18 for ( hypotenuse = 1; hypotenuse <= 500; hypotenuse++ )
19 {
Lab Exercises Name:
Lab Exercise 3 — Pythagorean Triples
Chapter 5 Control Statements: Part 2 185
Break in second for loop:
20 if ( numberOfTriples >= 20 )
21 break;
22
23 counter++;
24
25 // use Pythagorean Theorem to print right triangles
26 if ( ( side1 * side1 ) + ( side2 * side2 ) ==
27 ( hypotenuse * hypotenuse ) )
28 {
29 System.out.printf( "s1: %d, s2: %d, h: %d\n",
30 side1, side2, hypotenuse );
31 numberOfTriples++;
32 } // end if
33 } // end for
34
35 System.out.printf( "The inner loop iterated %d times.\n", counter );
36 } // end main
37 } // end class Triples1
s1: 3, s2: 4, h: 5
s1: 4, s2: 3, h: 5
s1: 5, s2: 12, h: 13
s1: 6, s2: 8, h: 10
s1: 7, s2: 24, h: 25
s1: 8, s2: 6, h: 10
s1: 8, s2: 15, h: 17
s1: 9, s2: 12, h: 15
s1: 9, s2: 40, h: 41
s1: 10, s2: 24, h: 26
s1: 11, s2: 60, h: 61
s1: 12, s2: 5, h: 13
s1: 12, s2: 9, h: 15
s1: 12, s2: 16, h: 20
s1: 12, s2: 35, h: 37
s1: 13, s2: 84, h: 85
s1: 14, s2: 48, h: 50
s1: 15, s2: 8, h: 17
s1: 15, s2: 20, h: 25
s1: 15, s2: 36, h: 39
The inner loop iterated 3517539 times.
1 // Lab 3: Triples2.java
2 // Program calculates Pythagorean triples
3 public class Triples2
4 {
5 public static void main( String args[] )
6 {
7 // declare the three sides of a triangle
8 int side1;
9 int side2;
10 int hypotenuse;
11 int counter = 0;
12 int numberOfTriples = 0;
Lab Exercises Name:
Lab Exercise 3 — Pythagorean Triples
186 Control Statements: Part 2 Chapter5
13
14 for ( side1 = 1; side1 <= 500; side1++ )
15
16 for ( side2 = 1; side2 <= 500; side2++ )
17 {
18 if ( numberOfTriples >= 20 )
19 break;
20
21 for ( hypotenuse = 1; hypotenuse <= 500; hypotenuse++ )
22 {
23 counter++;
24
25 // use Pythagorean Theorem to print right triangles
26 if ( ( side1 * side1 ) + ( side2 * side2 ) ==
27 ( hypotenuse * hypotenuse ) )
28 {
29 System.out.printf( "s1: %d, s2: %d, h: %d\n",
30 side1, side2, hypotenuse );
31 numberOfTriples++;
32 } // end if
33 } // end inner for
34 } // end middle for
35
36 System.out.printf( "The inner loop iterated %d times.\n", counter );
37 } // end main
38 } // end class Triples2
s1: 3, s2: 4, h: 5
s1: 4, s2: 3, h: 5
s1: 5, s2: 12, h: 13
s1: 6, s2: 8, h: 10
s1: 7, s2: 24, h: 25
s1: 8, s2: 6, h: 10
s1: 8, s2: 15, h: 17
s1: 9, s2: 12, h: 15
s1: 9, s2: 40, h: 41
s1: 10, s2: 24, h: 26
s1: 11, s2: 60, h: 61
s1: 12, s2: 5, h: 13
s1: 12, s2: 9, h: 15
s1: 12, s2: 16, h: 20
s1: 12, s2: 35, h: 37
s1: 13, s2: 84, h: 85
s1: 14, s2: 48, h: 50
s1: 15, s2: 8, h: 17
s1: 15, s2: 20, h: 25
s1: 15, s2: 36, h: 39
The inner loop iterated 3518000 times.
Lab Exercises Name:
Lab Exercise 3 — Pythagorean Triples
Chapter 5 Control Statements: Part 2 187
Break in outermost for loop:
1 // Lab 3: Triples3.java
2 // Program calculates Pythagorean triples
3 public class Triples3
4 {
5 public static void main( String args[] )
6 {
7 // declare the three sides of a triangle
8 int side1;
9 int side2;
10 int hypotenuse;
11 int counter = 0;
12 int numberOfTriples = 0;
13
14 for ( side1 = 1; side1 <= 500; side1++ )
15 {
16 if ( numberOfTriples >= 20 )
17 break;
18
19 for ( side2 = 1; side2 <= 500; side2++ )
20
21 for ( hypotenuse = 1; hypotenuse <= 500; hypotenuse++ )
22 {
23 counter++;
24
25 // use Pythagorean Theorem to print right triangles
26 if ( ( side1 * side1 ) + ( side2 * side2 ) ==
27 ( hypotenuse * hypotenuse ) )
28 {
29 System.out.printf( "s1: %d, s2: %d, h: %d\n",
30 side1, side2, hypotenuse );
31 numberOfTriples++;
32 } // end if
33 } // end inner for
34 } // end outer for
35
36 System.out.printf( "The inner loop iterated %d times.\n", counter );
37 } // end main
38 } // end class Triples3
Lab Exercises Name:
Lab Exercise 3 — Pythagorean Triples
188 Control Statements: Part 2 Chapter5
The break statement placed inside the innermost loop will exit the innermost loop, but not the outer two
loops. Those two loops will continue to run, but no processing of triples will occur. The innermost loop
will execute exactly enough times to find 20 triples. When the break statement is placed in the second
loop, the innermost loop will finish its 500 iterations even after finding the twentieth triple. After the first
time the second loop is reached after the twentieth triple is found, no more processing of triples will occur.
When the break statement is placed in the outermost loop, both inner loop will have to complete after the
twentieth triple is found. Only after these two loops complete will the break statement be reached.
3. Add a continue statement to the program that prevents a Pythagorean triple from being found when side1
is equal to 8. Using the loop counter again from Follow-Up Question 1, calculate how many times this new
program executed the innermost for loop. Explain how the continue statement affected the output.
s1: 3, s2: 4, h: 5
s1: 4, s2: 3, h: 5
s1: 5, s2: 12, h: 13
s1: 6, s2: 8, h: 10
s1: 7, s2: 24, h: 25
s1: 8, s2: 6, h: 10
s1: 8, s2: 15, h: 17
s1: 9, s2: 12, h: 15
s1: 9, s2: 40, h: 41
s1: 10, s2: 24, h: 26
s1: 11, s2: 60, h: 61
s1: 12, s2: 5, h: 13
s1: 12, s2: 9, h: 15
s1: 12, s2: 16, h: 20
s1: 12, s2: 35, h: 37
s1: 13, s2: 84, h: 85
s1: 14, s2: 48, h: 50
s1: 15, s2: 8, h: 17
s1: 15, s2: 20, h: 25
s1: 15, s2: 36, h: 39
s1: 15, s2: 112, h: 113
The inner loop iterated 3750000 times.
1 // Lab 3: Triples.java
2 // Program calculates Pythagorean triples
3 public class Triples
4 {
5 public static void main( String args[] )
6 {
7 // declare the three sides of a triangle
8 int side1;
9 int side2;
10 int hypotenuse;
11 int counter = 0;
12
13 for ( side1 = 1; side1 <= 500; side1++ )
14 {
15 if ( side1 == 8 )
16 continue;
17
18 for ( side2 = 1; side2 <= 500; side2++ )
19
Lab Exercises Name:
Lab Exercise 3 — Pythagorean Triples
Chapter 5 Control Statements: Part 2 189
The continue statement affects the output by skipping an iteration of the outer for loop. This results in
250,000 (500 * 500) less iterations of the inner loop.
20 for ( hypotenuse = 1; hypotenuse <= 500; hypotenuse++ )
21 {
22 counter++;
23
24 // use Pythagorean Theorem to print right triangles
25 if ( ( side1 * side1 ) + ( side2 * side2 ) ==
26 ( hypotenuse * hypotenuse ) )
27 System.out.printf( "s1: %d, s2: %d, h: %d\n",
28 side1, side2, hypotenuse );
29 } // end inner for
30 } // end outer for
31
32 System.out.printf( "The inner loop iterated %d times.\n", counter );
33 } // end main
34 } // end class Triples
s1: 3, s2: 4, h: 5
s1: 4, s2: 3, h: 5
s1: 5, s2: 12, h: 13
s1: 6, s2: 8, h: 10
s1: 7, s2: 24, h: 25
.
.
.
s1: 480, s2: 31, h: 481
s1: 480, s2: 88, h: 488
s1: 480, s2: 108, h: 492
s1: 480, s2: 140, h: 500
s1: 483, s2: 44, h: 485
The inner loop iterated 124750000 times.
Chapter 5 Control Statements: Part 2 197
Postlab Activities
Name: Date:
Section:
Coding Exercises
These coding exercises reinforce the lessons learned in the lab and provide additional programming experience
outside the classroom and laboratory environment. They serve as a review after you have successfully completed
the Prelab Activities and Lab Exercises.
For each of the following problems, write a program or a program segment that performs the specified action.
1. Write a for loop that prints all the odd integers from 1 to 100, inclusive.
2. Write a do…while loop that prints the integers from 10 to 0, inclusive.
3. Write a for loop that counts from 1 to 5. Use a switch statement to display a letter in the alphabet that
corresponds to the number (i.e., 1 is A, 2 is B, etc.).
1 for ( int i = 1; i <= 100; i++ )
2
3 if ( i % 2 == 1 )
4 printf( "%d ", i );
1 int i = 10;
2
3 do
4 {
5 printf( "%d ", i );
6 i--;
7 } while ( i >= 0 );
1 for ( int i = 1; i <= 5; i++ )
2 {
3 switch ( i )
4 {
5 case 1:
6 printf( "A" );
7 break;
8
9 case 2:
10 printf( "B" );
11 break;
12
13 case 3:
14 printf( "C" );
15 break;
16
Postlab Activities Name:
Coding Exercises
198 Control Statements: Part 2 Chapter5
4. Write a while loop that sums the integers from 1 to 10, excluding 3 and 6. Print the sum.
5. Write a for loop that attempts to display the numbers from 1 to 10, but terminates when the control vari-
able reaches the value 6.
6. Write a for loop to display the numbers from 1 to 10, but skip the value 6 by using a continue statement.
17 case 4:
18 printf( "D" );
19 break;
20
21 case 5:
22 printf( "E" );
23 break;
24 } // end switch
25 } // end for
1 int i = 1;
2 int sum = 0;
3
4 while ( i <= 10 )
5 {
6 if ( i == 3 || i == 6 )
7 continue;
8
9 sum += i
10 i++;
11 } // end while
12
13 printf( "sum: %d\n", sum );
1 for ( int i = 1; i <= 10; i++ )
2 {
3 if ( i == 6 )
4 break;
5
6 printf( "%d ", i );
7 } // end for
1 for ( int i = 1; i <= 10; i++ )
2 {
3 if ( i == 6 )
4 continue;
5
6 printf( "%d ", i );
7 } // end for
Postlab Activities Name:
Coding Exercises
Chapter 5 Control Statements: Part 2 199
7. Modify your solution in Coding Exercise 6 to use a while statement instead of a for statement.
8. Modify your solution in Coding Exercise 7 to use a do…while statement instead of a while statement.
1 int i = 1;
2
3 while ( i <= 10 )
4 {
5 if ( i == 6 )
6 continue;
7
8 printf( "%d ", i );
9 i++;
10 } // end while
1 int i = 1;
2
3 do
4 {
5 if ( i == 6 )
6 continue;
7
8 printf( "%d ", i );
9 i++;
10 } while ( i <= 10 )
Postlab Activities Name:
Programming Challenges
202 Control Statements: Part 2 Chapter5
2. (“The Twelve Days of Christmas” Song) Write an application that uses repetition and switch statements to
print the song “The Twelve Days of Christmas.” One switch statement should be used to print the day (i.e.,
“First,” “Second,” etc.). A separate switch statement should be used to print the remainder of each verse.
Visit the Web site www.12days.com/library/carols/12daysofxmas.htm for the complete lyrics of the
song.
Hints:
• For this example you will need two switch statements.
• Both switch statements should appear inside a for loop that will iterate through the twelve days.
• You will have one string to which more text is added during every iteration of the loop. The string will
be displayed after the loop terminates.
• Your output should appear as follows:
On the first day of Christmas, my true love gave to me:
a Partridge in a pear tree.
On the second day of Christmas, my true love gave to me:
Two turtle doves, and
a Partridge in a pear tree.
On the third day of Christmas, my true love gave to me:
Three French hens,
Two turtle doves, and
a Partridge in a pear tree.
On the fourth day of Christmas, my true love gave to me:
Four calling birds,
Three French hens,
Two turtle doves, and
a Partridge in a pear tree.
On the fifth day of Christmas, my true love gave to me:
Five golden rings.
Four calling birds,
Three French hens,
Two turtle doves, and
a Partridge in a pear tree.
On the sixth day of Christmas, my true love gave to me:
Six geese-a-laying,
Five golden rings.
Four calling birds,
Three French hens,
Two turtle doves, and
a Partridge in a pear tree.
On the seventh day of Christmas, my true love gave to me:
Seven swans-a-swimming,
Six geese-a-laying,
Five golden rings.
Four calling birds,
Three French hens,
Two turtle doves, and
a Partridge in a pear tree.
Postlab Activities Name:
Programming Challenges
Chapter 5 Control Statements: Part 2 203
On the eighth day of Christmas, my true love gave to me:
Eight maids-a-milking,
Seven swans-a-swimming,
Six geese-a-laying,
Five golden rings.
Four calling birds,
Three French hens,
Two turtle doves, and
a Partridge in a pear tree.
On the ninth day of Christmas, my true love gave to me:
Nine ladies dancing,
Eight maids-a-milking,
Seven swans-a-swimming,
Six geese-a-laying,
Five golden rings.
Four calling birds,
Three French hens,
Two turtle doves, and
a Partridge in a pear tree.
On the tenth day of Christmas, my true love gave to me:
Ten drummers drumming,
Nine ladies dancing,
Eight maids-a-milking,
Seven swans-a-swimming,
Six geese-a-laying,
Five golden rings.
Four calling birds,
Three French hens,
Two turtle doves, and
a Partridge in a pear tree.
On the eleventh day of Christmas, my true love gave to me:
Eleven pipers piping,
Ten drummers drumming,
Nine ladies dancing,
Eight maids-a-milking,
Seven swans-a-swimming,
Six geese-a-laying,
Five golden rings.
Four calling birds,
Three French hens,
Two turtle doves, and
a Partridge in a pear tree.
On the twelfth day of Christmas, my true love gave to me:
Twelve lords-a-leaping,
Eleven pipers piping,
Ten drummers drumming,
Nine ladies dancing,
Eight maids-a-milking,
Seven swans-a-swimming,
Six geese-a-laying,
Five golden rings.
Four calling birds,
Three French hens,
Two turtle doves, and
a Partridge in a pear tree.
Postlab Activities Name:
Programming Challenges
204 Control Statements: Part 2 Chapter5
Solution
1 // Programming Challenge 2: Twelve.java
2 // Program prints the 12 days of Christmas song.
3 public class Twelve
4 {
5 // print the 12 days of Christmas song
6 public void printSong()
7 {
8 for ( int day = 1; day <= 12; day++ )
9 {
10 System.out.print( "On the " );
11
12 // add correct day to String
13 switch ( day )
14 {
15 case 1:
16 System.out.print( "first" );
17 break;
18
19 case 2:
20 System.out.print( "second" );
21 break;
22
23 case 3:
24 System.out.print( "third" );
25 break;
26
27 case 4:
28 System.out.print( "fourth" );
29 break;
30
31 case 5:
32 System.out.print( "fifth" );
33 break;
34
35 case 6:
36 System.out.print( "sixth" );
37 break;
38
39 case 7:
40 System.out.print( "seventh" );
41 break;
42
43 case 8:
44 System.out.print( "eighth" );
45 break;
46
47 case 9:
48 System.out.print( "ninth" );
49 break;
50
51 case 10:
52 System.out.print( "tenth" );
53 break;
54
Postlab Activities Name:
Programming Challenges
Chapter 5 Control Statements: Part 2 205
55 case 11:
56 System.out.print( "eleventh" );
57 break;
58
59 case 12:
60 System.out.print( "twelfth" );
61 break;
62 } // end switch
63
64 System.out.println(
65 " day of Christmas, my true love gave to me:" );
66
67 // add remainder of verse to String
68 switch ( day )
69 {
70 case 12:
71 System.out.println( "Twelve lords-a-leaping," );
72
73 case 11:
74 System.out.println( "Eleven pipers piping," );
75
76 case 10:
77 System.out.println( "Ten drummers drumming," );
78
79 case 9:
80 System.out.println( "Nine ladies dancing," );
81
82 case 8:
83 System.out.println( "Eight maids-a-milking," );
84
85 case 7:
86 System.out.println( "Seven swans-a-swimming," );
87
88 case 6:
89 System.out.println( "Six geese-a-laying," );
90
91 case 5:
92 System.out.println( "Five golden rings." );
93
94 case 4:
95 System.out.println( "Four calling birds," );
96
97 case 3:
98 System.out.println( "Three French hens," );
99
100 case 2:
101 System.out.println( "Two turtle doves, and" );
102
103 case 1:
104 System.out.println( "a Partridge in a pear tree." );
105 } // end switch
106
107 System.out.println();
108 } // end for
109 } // end method printSong
110 } // end class Twelve
Postlab Activities Name:
Programming Challenges
206 Control Statements: Part 2 Chapter5
1 // Programming Challenge 2: TwelveTest.java
2 // Test application for class Twelve
3 public class TwelveTest
4 {
5 public static void main( String args[] )
6 {
7 Twelve application = new Twelve();
8 application.printSong();
9 } // end main
10 } // end class TwelveTest