COE 212 Problems Chapter 3 Solutions, Fall 2013

6th Edition, Java Software Solutions Disclaimer: In what follows, you will find the solutions to the exercises given in the 6th edition of the book. If you happen to be using an earlier edition of the book, you should match each one of the problems presented below to the proper exercise in the book that you have. So keep in mind that the order in which the solutions are listed may not agree with the order of the exercises in your book. Chapter 3 Exercise Solutions EX 1.1. Write a statement that prints the number of characters in a String object called overview. System.out.println (overview.length()); EX 1.2. Write a statement that prints the 8th character of a String object called introduction. System.out.println (introduction.charAt(7)); EX 1.3. Write a declaration for a String variable called change and initialize it to the characters stored in another String object called original with all 'e' characters changed to 'j'. String change = original.replace ('e', 'j'); EX 1.4. What output is produced by the following code fragment? String m1, m2, m3; m1 = "Quest for the Holy Grail"; m2 = m1.toLowerCase(); m3 = m1 + " " + m2; System.out.println (m3.replace('h', 'z')); The output produced is: Quest for tze Holy Grail quest for tze zoly grail The original string is concatenated with a lowercase version of itself, then all lowercase ‘h’ characters are replaced with ‘z’. EX 1.5. What is the effect of the following import statement? import java.awt.*; This statement allows the program in which it is written to access all classes (because of the wildcard *) in the package java.awt without any further reference to the package name. EX 1.6. Assuming that a Random object has been created called generator, what is the range of the result of each of the following expressions? a. generator.nextInt(20) 0 to 19, inclusive 6th Edition, Java Software Solutions b. generator.nextInt(8) + 1 1 to 8, incluslive c. generator.nextInt(45) + 10 10 to 54, inclusive d. generator.nextInt(100) – 50 -50 to 49, inclusive EX 1.7. Write code to declare and instantiate an object of the Random class (call the object reference variable rand). Then write a list of expressions using the nextInt method that generate random numbers in the following specified ranges, including the endpoints. Use the version of the nextInt method that accepts a single integer parameter. Random rand = new Random(); a. 0 to 10 rand.nextInt(11) b. 0 to 500 rand.nextInt(501) c. 1 to 10 rand.nextInt(10) + 1 d. 1 to 500 rand.nextInt(500) + 1 e. 25 to 50 rand.nextInt(26) + 25 f. –10 to 15 rand.nextInt(26) – 10 EX 1.8. Write an assignment statement that computes the square root of the sum of num1 and num2 and assigns the result to num3. num3 = Math.sqrt(num1 + num2); EX 1.9. Write a single statement that computes and prints the absolute value of total. System.out.println (Math.abs(total)); EX 1.10. Write code statements to create a DecimalFormat object that will round a formatted value to 4 decimal places. Then write a statement that uses that object to print the value of result, properly formatted. DecimalFormat fmt = new DecimalFormat (“0.####”); System.out.println (fmt.format(result)); EX 1.11. Write code statements that prompt for and read a double value from the user, and then print the result of raising that value to the fourth power. Output the results to 3 decimal places. Scanner scan = new Scanner (System.in); 6th Edition, Java Software Solutions DecimalFormat fmt = new DecimalFormat (“0.###”); System.out.println ("Enter a value: "); double num = scan.nextDouble(); System.out.println (fmt.format(Math.pow(num, 4))); EX 1.12. Write a declaration for an enumerated type that represents the days of the week. enum Days {sunday, monday, tuesday, wednesday, thursday, friday, saturday} Chapter 3 Programming Projects Solutions PP3.1 Refer to UsernameGenerator.java in the folder named “chap03ppsolutions” PP3.2 Refer to SumOfCubes.java in the folder named “chap03ppsolutions” PP3.3 Refer to PhoneNumbers.java in the folder named “chap03 pp solutions” PP3.4 Refer to DistanceCalculation.java in the folder named “chap03ppsolutions” PP3.5 Refer to SphereCalculations.java in the folder named “chap03ppsolutions” PP3.6 Refer to TriangleArea.java in the folder named “chap03 pp solutions” PP3.7 Refer to NameOrientation.java in the folder named “chap03 pp solutions” PP3.8 Refer to ImageOrientation.java in the folder named “chap03 pp solutions” PP3.9 Refer to LabelDemo2.java in the folder named “chap03 pp solutions” //******************************************************************** // DistanceCalculation.java Author: Lewis and Loftus // // Solution to Programming Project 3.4 (5th Ed, p. 153) //******************************************************************** import java.util.Scanner; public class DistanceCalculation { //----------------------------------------------------------------- // Computes the distance between two points using the distance // formula. //----------------------------------------------------------------- public static void main (String[] args) { int x1, y1, x2, y2; double distance; Scanner scan = new Scanner(System.in); System.out.println ("Enter the first coordinate values:"); x1 = scan.nextInt(); y1 = scan.nextInt(); System.out.println ("Enter the second coordinate values:"); x2 = scan.nextInt(); y2 = scan.nextInt(); distance = Math.sqrt( Math.pow(x2-x1, 2) + Math.pow(y2-y1, 2) ); System.out.println ("The distance between (" + x1 + "," + y1 + ") and (" + x2 + "," + y2 + ") is " + distance); } } //******************************************************************** // ImageOrientation.java Author: Lewis/Loftus // // Solution to Programming Project 3.8 (5th Ed, p. 154) //******************************************************************** import java.awt.*; import javax.swing.*; public class ImageOrientation { //----------------------------------------------------------------- // Displays images in panels with various constraints. //----------------------------------------------------------------- public static void main (String[] args) { JFrame frame = new JFrame ("Image Orientation"); frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE); JLabel label1 = new JLabel (new ImageIcon ("books.jpg")); JLabel label2 = new JLabel (new ImageIcon ("lightbulb.jpg")); JLabel label3 = new JLabel (new ImageIcon ("couple.jpg")); JLabel label4 = new JLabel (new ImageIcon ("dog.jpg")); JPanel panel1 = new JPanel(); panel1.setBackground (Color.green); panel1.setMinimumSize (new Dimension(300, 300)); panel1.add (label1); panel1.add (label2); JPanel panel2 = new JPanel(); panel2.setBackground (Color.yellow); panel2.add (label3); panel2.add (label4); JPanel primary = new JPanel(); primary.setBackground (Color.cyan); primary.add (panel1); primary.add (panel2); frame.getContentPane().add(primary); frame.pack(); frame.setVisible(true); } } //******************************************************************** // LabelDemo2.java Author: Lewis/Loftus // // Solution to Programming Project 3.9 (5th Ed, p. 154) //******************************************************************** import java.awt.*; import javax.swing.*; public class LabelDemo2 { //----------------------------------------------------------------- // Creates and displays the primary application frame. //----------------------------------------------------------------- public static void main (String[] args) { JFrame frame = new JFrame ("Label Demo 2"); frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE); ImageIcon icon = new ImageIcon ("devil.gif"); JLabel label1, label2, label3, label4; label1 = new JLabel ("Devil Left", icon, SwingConstants.LEFT); label2 = new JLabel ("Devil Right", icon, SwingConstants.LEFT); label2.setHorizontalTextPosition (SwingConstants.LEFT); label2.setVerticalTextPosition (SwingConstants.BOTTOM); label3 = new JLabel ("Devil Above", icon, SwingConstants.LEFT); label3.setHorizontalTextPosition (SwingConstants.CENTER); label3.setVerticalTextPosition (SwingConstants.BOTTOM); label4 = new JLabel ("Devil Below", icon, SwingConstants.LEFT); label4.setHorizontalTextPosition (SwingConstants.CENTER); label4.setVerticalTextPosition (SwingConstants.TOP); JPanel panel = new JPanel(); panel.setBackground (Color.cyan); panel.setPreferredSize (new Dimension (200, 250)); panel.add (label1); panel.add (label2); panel.add (label3); panel.add (label4); frame.getContentPane().add(panel); frame.pack(); frame.setVisible(true); } } //******************************************************************** // NameOrientation.java Author: Lewis/Loftus // // Solution to Programming Project 3.7 (5th Ed, p. 154) //******************************************************************** import java.awt.*; import javax.swing.*; public class NameOrientation { //----------------------------------------------------------------- // Displays a name such that the orientation of the first and // last names change with the size of the window. //----------------------------------------------------------------- public static void main (String[] args) { JFrame frame = new JFrame ("Name Orientation"); frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE); ImageIcon icon = new ImageIcon ("devil.gif"); JPanel primary = new JPanel(); primary.setBackground (Color.cyan); primary.setPreferredSize (new Dimension(200, 50)); JLabel firstName = new JLabel ("Elizabeth"); JLabel lastName = new JLabel ("Montgomery"); primary.add (firstName); primary.add (lastName); frame.getContentPane().add(primary); frame.pack(); frame.setVisible(true); } } //******************************************************************** // PhoneNumbers.java Author: Lewis and Loftus // // Solution to Programming Project 3.3 (5th Ed, p. 153) //******************************************************************** import java.util.Random; public class PhoneNumbers { //----------------------------------------------------------------- // Produces a random phone number with various constraints. //----------------------------------------------------------------- public static void main (String[] args) { String result = ""; Random rand = new Random(); // none of the first three digits is higher than 7 result += rand.nextInt(8); result += rand.nextInt(8); result += rand.nextInt(8); result += "-"; // the next set of digits cannot be greater than 742 result += rand.nextInt(643) + 100; result += "-"; result += rand.nextInt(9000) + 1000; System.out.println ("A random phone number: " + result); } } This folder contains solutions to the Programming Projects from Chapter 3 of Java Software Solutions, 5th Ed, by Lewis and Loftus. Project File(s) ------- ------- 3.1 UsernameGenerator.java 3.2 SumOfCubes.java 3.3 PhoneNumbers.java 3.4 DistanceCalculation.java 3.5 SphereCalculations.java 3.6 TriangleArea.java 3.7 NameOrientation.java 3.8 ImageOrientation.java books.jpg lightbulb.jpg couple.jpg dog.jpg 3.9 LabelDemo2.java devil.gif //******************************************************************** // SphereCalculations.java Author: Lewis and Loftus // // Solution to Programming Project 3.5 (5th Ed, p. 154) //******************************************************************** import java.util.Scanner; import java.text.DecimalFormat; public class SphereCalculations { //----------------------------------------------------------------- // Computes the volume and surface area of a sphere given its // radius. //----------------------------------------------------------------- public static void main (String[] args) { double radius, area, volume; Scanner scan = new Scanner(System.in); System.out.print ("Enter the sphere's radius: "); radius = scan.nextDouble(); volume = 4.0 / 3.0 * Math.PI * Math.pow(radius, 3); area = 4 * Math.PI * Math.pow(radius, 2); DecimalFormat fmt = new DecimalFormat ("0.####"); System.out.println ("Volume: " + fmt.format(volume)); System.out.println ("Surface area: " + fmt.format(area)); } } //******************************************************************** // SumOfCubes.java Author: Lewis and Loftus // // Solution to Programming Project 3.2 (5th Ed, p. 153) //******************************************************************** import java.util.Scanner; public class SumOfCubes { //----------------------------------------------------------------- // Calculates the sum of two cubed integers. //----------------------------------------------------------------- public static void main (String[] args) { int num1, num2, value; Scanner scan = new Scanner(System.in); System.out.print ("Enter two integers: "); num1 = scan.nextInt(); num2 = scan.nextInt(); value = (int) (Math.pow(num1, 3) + Math.pow(num2, 3)); System.out.println ("Sum of cubes: " + value); } } //******************************************************************** // TriangleArea.java Author: Lewis and Loftus // // Solution to Programming Project 3.6 (5th Ed, p. 154) //******************************************************************** import java.util.Scanner; import java.text.DecimalFormat; public class TriangleArea { //----------------------------------------------------------------- // Computes the area of a triangle given the length of each // side. Uses Heron's formula. //----------------------------------------------------------------- public static void main (String[] args) { double side1, side2, side3, s, area; Scanner scan = new Scanner(System.in); System.out.print ("Enter the length of side 1: "); side1 = scan.nextDouble(); System.out.print ("Enter the length of side 2: "); side2 = scan.nextDouble(); System.out.print ("Enter the length of side 3: "); side3 = scan.nextDouble(); s = (side1 + side2 + side3) / 2; // half of the perimeter area = Math.sqrt (s * (s-side1) * (s-side2) * (s-side3)); DecimalFormat fmt = new DecimalFormat ("0.###"); System.out.println ("Area: " + fmt.format(area)); } } //******************************************************************** // UsernameGenerator.java Author: Lewis and Loftus // // Solution to Programming Project 3.1 (5th Ed, p. 153) //******************************************************************** import java.util.Scanner; import java.util.Random; public class UsernameGenerator { //----------------------------------------------------------------- // Produces a username based on the user's first and last names. // Assumes the last name is at least five characters long (see // errata). //----------------------------------------------------------------- public static void main (String[] args) { String first, last, username; Scanner scan = new Scanner(System.in); Random rand = new Random(); System.out.print ("Enter your first name: "); first = scan.nextLine(); System.out.print ("Enter your last name: "); last = scan.nextLine(); username = first.charAt(0) + last.substring(0, 5) + (rand.nextInt(90) + 10); System.out.println ("Username: " + username); } }