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Java Methods A & AB:
Object-Oriented Programming and Data Structures

Answers and Solutions to Exercises

Chapter 8

1.   public class Population { private final double growthRate = 1.017; // 1.7% increase per year public static void main(String[] args) { double population = 106.2, target = 120.0; int year = 2005; while (population < target) { population *= growthRate; year++; } System.out.println("The population will reach " + target + " million in " + year); } }
3.   public static int addOdds(int n) { int sum = 0; for (int i = 1; i < n; i += 2) sum += i; return sum; }
5.   public static void main(String[] args) { Scanner input = new Scanner(System.in); int sum = 0; System.out.print("Enter a positive integer under 10: "); int n = input.nextInt(); for (int i = 1; i <= n; i++) { if (i > 1) System.out.print(" + "); System.out.print(i); sum += i; } System.out.println(" = " + sum); }
6. (a) public static boolean isPrime(int n) { if (n < 3) return n == 2; else if (n % 2 == 0) return false; int m = 3; while (m * m <= n) { if (n % m == 0) return false; m += 2; } return true; }
(b) public static boolean isPrime(int n) { if (n < 5) return n == 2 || n == 3; else if (n % 2 == 0 || n % 3 == 0) return false; int m = 5; while (m * m <= n) { if (n % m == 0 || n % (m + 2) == 0) return false; m += 6; } return true; }
7.   public static boolean isPerfectSquare(int n) { int p = 1, sum = 0; while (sum < n) { sum += p; p += 2; } return sum == n; }

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