Included below are short-answer and programming exercises. Answers are provided for those exercises whose exercise number is a hyperlink. Because college faculty use these exercises in their exams, we have provided answers to roughly half of the exercises included here.
2.7 Fill in the blanks in each of the following:
2.8 Write Java statements that accomplish each of the following:
2.9 State which of the following are true and which are false. If false, explain why.
2.10 Fill in the blanks in each of the following:
2.11 What displays in the message dialog when each of the following Java statements is performed? Assume x = 2 and y = 3.
2.12 Which of the following Java statements contain variables whose values are destroyed (i.e., changed or replaced)?
2.13 Given y = ax3 + 7, which of the following are correct statements for this equation?
2.14 State the order of evaluation of the operators in each of the following Java statements and show the value of x after each statement is performed.
2.15 Write an application that displays the numbers 1 to 4 on the same line with each pair of adjacent numbers separated by one space. Write the program using the following methods.
2.16 Write an application that asks the user to enter two numbers, obtains the two numbers from the user and prints the sum, product, difference and quotient of the two numbers. Use the techniques shown in Fig. 2.8. 2.17 Write an application that asks the user to enter two integers, obtains the numbers from the user and displays the larger number followed by the words "is larger" in an information message dialog. If the numbers are equal, print the message "These numbers are equal." Use the techniques shown in Fig. 2.17. 2.18 Write an application that inputs three integers from the user and displays the sum, average, product, smallest and largest of these numbers in an information message dialog. Use the GUI techniques shown in Fig. 2.17. Note: The average calculation in this exercise should result in an integer representation of the average. So, if the sum of the values is 7, the average will be 2 not 2.3333... 2.19 Write an application that inputs from the user the radius of a circle and prints the circle’s diameter, circumference and area. Use the constant value 3.14159 for p. Use the GUI techniques shown in Fig. 2.8. [Note: You may also use the predefined constant Math.PI for the value of p. This constant is more precise than the value 3.14159. Class Math is defined in the java.lang package, so you do not need to import it.] Use the following formulas (r is the radius): diameter = 2r, circumference = 2pr, area = pr2. 2.20 Write an application that displays in the command window a box, an oval, an arrow and a diamond using asterisks (*) as follows:
2.21 Modify the program you created in Exercise 2.20 to display the shapes in a JOptionPane.PLAIN_MESSAGE dialog. Does the program display the shapes exactly as in Exercise 2.20? 2.22 What does the following code print? System.out.println( "*\n**\n***\n****\n*****" ); 2.23 What does the following code print? System.out.println( "*" ); 2.24 What does the following code print? System.out.print( "*" ); 2.25 What does the following code print? System.out.print( "*" ); 2.26 Write an application that reads five integers and determines and prints the largest and the smallest integers in the group. Use only the programming techniques you learned in this chapter. 2.27 Write an application that reads an integer and determines and prints whether it is odd or even. (Hint: Use the modulus operator. An even number is a multiple of two. Any multiple of two leaves a remainder of zero when divided by 2.) 2.28 Write an application that reads in two integers and determines and prints if the first is a multiple of the second. (Hint: Use the modulus operator.) 2.29 Write an application that displays in the command window a checkerboard pattern as follows:
2.30 Modify the program you wrote in Exercise 2.29 to display the checkerboard pattern in a JOptionPane.PLAIN_MESSAGE dialog. Does the program display the shapes exactly as in Exercise 2.29? 2.31 Here's a peek ahead. In this chapter you learned about integers and the data type int. Java can also represent uppercase letters, lowercase letters and a considerable variety of special symbols. Every character has a corresponding integer representation. The set of characters a computer uses and the corresponding integer representations for those characters is called that computer’s character set. You can indicate a character value in a program by simply enclosing that character in single quotes as with 'A'. (int) 'A' System.out.println( When the preceding statement executes, it displays the character A and the value 65 (from the so- called Unicode character set) as part of the string. 2.32 Write an application that inputs one number consisting of five-digits from the user, separates the number into its individual digits and prints the digits separated from one another by three spaces each. For example, if the user types in the number 42339, the program should print
2.33 Using only the programming techniques you learned in this chapter, write an application that calculates the squares and cubes of the numbers from 0 to 10 and prints the resulting values in table format as follows:
2.34 Write a program that reads a first name and a last name from the user as two separate inputs and concatenates the first name and last name separated by a space. Display in a message dialog the concatenated name. 2.35 Write a program that inputs five numbers and determines and prints the number of negative numbers input, number of positive numbers input and the number of zeros input. |
Included below are answers to approximately half the of the exercises in the Cyber Classroom. We are not able to include answers to every exercise because college faculty use these exercises in their classroom exams.
2.7 Fill in the blanks in each of the following:
2.9 State which of the following are true and which are false. If false, explain why.
2.11 What displays in the message dialog when each of the following Java statements is performed? Assume x = 2 and y = 3.
// Exercise 2.17 Solution
// Larger.java
// Program determines the larger of two numbers
import javax.swing.JOptionPane;
public class Larger {
public static void main( String args[] )
{
String firstNumber, // first string entered by user
secondNumber, // second string entered by user
result; // a string containing the output
int number1, // first number to compare
number2; // second number to compare
// read first number from user as a string
firstNumber =
JOptionPane.showInputDialog( "Enter first integer:" );
// read second number from user as a string
secondNumber =
JOptionPane.showInputDialog( "Enter second integer:" );
// convert numbers from type String to type int
number1 = Integer.parseInt( firstNumber );
number2 = Integer.parseInt( secondNumber );
if ( number1 > number2 )
result = number1 + " is larger.";
else if ( number1 < number2 )
result = number2 + " is larger.";
else
result = "These numbers are equal.";
// Display results
JOptionPane.showMessageDialog(
null, result, "Comparison Results",
JOptionPane.INFORMATION_MESSAGE );
System.exit( 0 );
}
}
// Exercise 2.19 Solution
// Circle.java
// Program calculate the area, circumference, and diameter for a circle
import javax.swing.JOptionPane;
public class Circle {
public static void main( String args[] )
{
String input, // string entered by user
result; // output display string
int radius; // radius of circle
// read from user as a string
input =
JOptionPane.showInputDialog( "Enter radius:" );
// convert number from type String to type int
radius = Integer.parseInt( input );
result = "Diameter is " + ( 2 * radius ) +
"\nArea is " + ( Math.PI * radius * radius ) +
"\nCircumference is " + ( 2 * Math.PI * radius );
// Display results
JOptionPane.showMessageDialog(
null, result, "Calculation Results",
JOptionPane.INFORMATION_MESSAGE );
System.exit( 0 );
}
}
2.24 What does the following code print? System.out.print( "*" ); // Exercise 2.27 Solution
// OddEven.java
// Program determines if a number is odd or even
import javax.swing.JOptionPane;
public class OddEven {
public static void main( String args[] )
{
String input, // string entered by user
result; // output display string
int number; // number
// read from user as a string
input =
JOptionPane.showInputDialog( "Enter integer:" );
// convert number from type String to type int
number = Integer.parseInt( input );
if ( number % 2 == 0 )
result = "Number is even.";
else
result = "Number is odd.";
// Display results
JOptionPane.showMessageDialog(
null, result, "Calculation Results",
JOptionPane.INFORMATION_MESSAGE );
System.exit( 0 );
}
}
// Exercise 2.29 Solution
// Checker.java
// Program draws a checkerboard
public class Checker {
public static void main( String args[] )
{
System.out.println( "* * * * * * * *" );
System.out.println( " * * * * * * * *" );
System.out.println( "* * * * * * * *" );
System.out.println( " * * * * * * * *" );
System.out.println( "* * * * * * * *" );
System.out.println( " * * * * * * * *" );
System.out.println( "* * * * * * * *" );
System.out.println( " * * * * * * * *" );
}
}
// Exercise 2.31 Solution
// Display.java
// Program prints a unicode character
// and its integer equivalent
public class Display {
public static void main( String args[] )
{
System.out.println( "The character " + 'A' +
" has the value " + ( int ) 'A' );
System.out.println( "The character " + 'B' +
" has the value " + ( int ) 'B' );
System.out.println( "The character " + 'C' +
" has the value " + ( int ) 'C' );
System.out.println( "The character " + 'a' +
" has the value " + ( int ) 'a' );
System.out.println( "The character " + 'b' +
" has the value " + ( int ) 'b' );
System.out.println( "The character " + 'c' +
" has the value " + ( int ) 'c' );
System.out.println( "The character " + '0' +
" has the value " + ( int ) '0' );
System.out.println( "The character " + '1' +
" has the value " + ( int ) '1' );
System.out.println( "The character " + '2' +
" has the value " + ( int ) '2' );
System.out.println( "The character " + '$' +
" has the value " + ( int ) '$' );
System.out.println( "The character " + '*' +
" has the value " + ( int ) '*' );
System.out.println( "The character " + '/' +
" has the value " + ( int ) '/' );
System.out.println( "The character " + ' ' +
" has the value " + ( int ) ' ' );
System.out.println( "The character " + ',' +
" has the value " + ( int ) ',' );
}
}
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