Solve file:///X|/cs101/Homework2_0.txt
/*
== 3.5 from page 94 == Write a program that generates three single-digit integers and prompt the user to enter the addition of these three integers.
*/ import java.util.Scanner; public class Homework2_0 { public static void main(String[] args) { // generate the three integers. int num1 = (int) (Math.random() * 10); int num2 = (int) (Math.random() * 10); int num3 = (int) (Math.random() * 10); // prompt the user. System.out.print(num1 + " + " + num2 + " + " + num3 + " = "); Scanner input = new Scanner(System.in); if (input.nextInt() == num1 + num2 + num3) { System.out.print("Correct!"); } else { System.out.print("Incorrect! The answer was " + (num1 + num2 + num3) + "."); } // no errors. System.exit(0); } }
file:///X|/cs101/Homework2_0.txt [4/29/2008 12:10:00 PM]
file:///X|/cs101/Homework2_1.txt
/*
== Solve 3.8 from page 94 == Write a program that sorts three integers. The integers are entered from the input dialogs and stored in variables num1, num2, and num3, respectively. The program sorts the numbers os that num1 <= num2 <= num3.
*/ import javax.swing.JOptionPane; public class Homework2_1 { public static void main(String[] args) { // prompt the user for the integers. int num1 = Integer.parseInt(JOptionPane.showInputDialog(null,"Enter the first integer:", "Homework2_1 Input",JOptionPane.QUESTION_MESSAGE)); int num2 = Integer.parseInt(JOptionPane.showInputDialog(null,"Enter the second integer:", "Homework2_1 Input",JOptionPane.QUESTION_MESSAGE)); int num3 = Integer.parseInt(JOptionPane.showInputDialog(null,"Enter the third integer:", "Homework2_1 Input",JOptionPane.QUESTION_MESSAGE)); // use a stacked bubble sort. int swap; while (num1 > num2) { swap = num2; num2 = num1; num1 = swap; if (num2 > num3) { swap = num3; num3 = num2; num2 = swap; } } // print the result. JOptionPane.showMessageDialog(null,num1 + " <= " + num2 + " <= " + num3); // no errors. System.exit(0); } }
file:///X|/cs101/Homework2_1.txt [4/29/2008 12:10:00 PM]
file:///X|/cs101/Homework2_2.txt
/* == Solve 3.9 from page 94 == Write a program that reads three edges for a triangle and computes the perimeter if the perimeter if the input is valid. Otherwise, display that the input is invalid. The input is valid if the sum of any two edges is greater than the third edge. */ import java.util.Scanner; public class Homework2_2 { public static void main(String[] args) { // prompt the user for the edge lengths. Scanner input = new Scanner(System.in); System.out.print("Enter the first edge length: "); int edge1 = input.nextInt(); the System.out.print("Enter second edge length: "); int edge2 = input.nextInt(); System.out.print("Enter the third edge length: "); int edge3 = input.nextInt(); // test the input for validity. if (!((edge1 + edge2 > edge3) && (edge1 + edge3 > edge2) && (edge2 + edge3 > edge1))) { System.out.print("Invalid input! The sum of any two edges must be great than the third."); System.exit(1); } // compute and display the perimeter. System.out.print("The perimeter of a " + edge1 + "-" + edge2 + "-" + edge3 + " triangle is " + (edge1 + edge2 + edge3) + "."); // no errors. System.exit(0); } }
file:///X|/cs101/Homework2_2.txt [4/29/2008 12:10:00 PM]
file:///X|/cs101/Homework2_3.txt
/* == Solve 3.11 from page 94 == Write a program that prompts the user to enter the month and year, and display the number of days in the month. For example, if the user enter month 2 and year 2000, the program should display that February has 29 days. If the user entered month 3 and year 2005, the program should display that March 2005 has 31 days. */ import java.util.Scanner; public class Homework2_3 { public static void main(String[] args) { // set up the array of month strings. String[] months = {"January","February","March","April","May","June","July","August","Septemeber","October","November","December"}; // prompt the user for a month and year. Scanner input = new Scanner(System.in); System.out.print("Enter a month, where 1 = January and 12 = December: "); int month = input.nextInt(); System.out.print("Enter a four-digit year: "); int year = input.nextInt(); // break the logic into months. int days = 0; switch(month) { case 1: // January case 3: // March case 5: // May case 7: // July case 8: // August case 10: // October case 12: // December days = 31; break; case 4: // April case 6: // July case 9: // September case 11: // November
file:///X|/cs101/Homework2_3.txt (1 of 2) [4/29/2008 12:10:01 PM]
file:///X|/cs101/Homework2_3.txt
days = 30; break; case 2: // February if ((year % 4 == 0) && ((year % 100 != 0) || (year % 400 == 0))) { days = 29; } else { days = 28; } break; default: // non-existant month. System.out.print(month + " does not correspond to a valid month in the Gregorian calender."); System.exit(1); } // output the result string. System.out.print(months[month-1] + " " + year + " has " + days + " days."); // no errors. System.exit(0); } }
file:///X|/cs101/Homework2_3.txt (2 of 2) [4/29/2008 12:10:01 PM]