Question

class Loops{

public void printNumbers(int low, int high){
// using a for loop, print all numbers from low to high
for(int i = low; i <= high; i++){
System.out.println(i);
}
}
public int sumOfNumbers(int n){
// using a for loop, calculate and return the sum of first n numbers
// i.e n = 5, answer = 5+4+3+2+1 = 15
int sum = 0;
for(int i = 1; i <= n; i++){
sum += i;
}
return sum;
}
public void printMultiplicationTable(int num){
// using a for loop, print the multiplication table of num (up to first 10!)
// i.e. num = 5, 5*1=5, 5*2=10, 5*3=15, 5*4=20, 5*5=25, 5*6=30, 5*7=35...
for(int i = 1; i <= 10; i++){
System.out.println(num + " * " + i + "=" + (num *i));
}
}
public int getFactorialOfNum(int num){
// using for loop, calculate and return the factorial of number
// i.e. factorial of 4 is: 4*3*2*1 = 24
// i.e. factorial of 5 is: 5*4*3*2*1 = 120
for(int i = 1; i <= num; i++){
factorial = factorial * i;
}
System.out.println("Factorial of "+ num +" is: "+ factorial);
}
public int pow(int base, int power){
// using for loop, calculate base raised to power
// i.e. base = 2, power = 3 = 2^3 = 2*2*2 = 8
// i.e. base = 5, power = 4 = 5^4 = 5*5*5*5 = 625
int p = 1;
for(int i = 0; i < power; i++){
p *= base;
}
return p;
}
public String reverseMyString(String input){
// using a loop, reverse a string
// i.e. input = "hello", reversed answer: "olleh"
// i.e. input = "bye", reversed answer: "eyb"
String reverse = " ";
for(int i = 0; i < input.length(); i++){
reverse = input.chartAt(i) + reverse;
}
return reverse;
}
public boolean isEven(int num){
// return true if the number is even, false otherwise
for (int i = 0; i <= 10; i++){
if(i % 2 == 0) {
return true;
}
}
}
public boolean isOdd(int num){
// return true if the number is odd, false otherwise
for(int i = 0; i <= 10; i++){
if(i % 2 != 0){
return true;
}
}
}
public boolean isPrime(int num){
// return true if the number is prime, false otherwise
for(int i = 2; i < num; ++i){
if(num % 1 == 0){
return false;
}
}
return num > 1;
}
}

Write a LoopsDriver:

• Write an infinite loop which does the following
  • Prints a menu of 10 options (9 methods that the user is allowed to call, 0 to exit)
  • Asks the user which method to call
  • Asks the user to enter the appropriate argument
    • reverseMyString needs a String from the user
    • isPrime needs an integer from the user
    • pow needs 2 integers from the user
  • Calls the method and prints out the answer

Answer 1

Java code

import java.util.Scanner;

class Loops {

    public void printNumbers(int low, int high) {

        // using a for loop, print all numbers from low to high

        for (int i = low; i <= high; i++) {

            System.out.println(i);

        }

    }

    public int sumOfNumbers(int n) {

        // using a for loop, calculate and return the sum of first n numbers

        // i.e n = 5, answer = 5+4+3+2+1 = 15

        int sum = 0;

        for (int i = 1; i <= n; i++) {

            sum += i;

        }

        return sum;

    }

    public void printMultiplicationTable(int num) {

        // using a for loop, print the multiplication table of num (up to first 10!)

        // i.e. num = 5, 5*1=5, 5*2=10, 5*3=15, 5*4=20, 5*5=25, 5*6=30, 5*7=35...

        for (int i = 1; i <= 10; i++) {

            System.out.println(num + " * " + i + "=" + (num * i));

        }

    }

    public void getFactorialOfNum(int num) {

        int factorial = 1;

        for (int i = 1; i <= num; i++) {

            factorial = factorial * i;

        }

        System.out.println("Factorial of " + num + " is: " + factorial);

    }

    public int pow(int base, int power) {

        // using for loop, calculate base raised to power

        // i.e. base = 2, power = 3 = 2^3 = 2*2*2 = 8

        // i.e. base = 5, power = 4 = 5^4 = 5*5*5*5 = 625

        int p = 1;

        for (int i = 0; i < power; i++) {

            p *= base;

        }

        return p;

    }

    public String reverseMyString(String input) {

        // using a loop, reverse a string

        // i.e. input = "hello", reversed answer: "olleh"

        // i.e. input = "bye", reversed answer: "eyb"

        String reverse = " ";

        for (int i = 0; i < input.length(); i++) {

            reverse = input.charAt(i) + reverse;

        }

        return reverse;

    }

    public boolean isEven(int num) {

        return num % 2 == 0;

    }

    public boolean isOdd(int num) {

        return num % 2 == 1;

    }

    public boolean isPrime(int num) {

        // return true if the number is prime, false otherwise

        for (int i = 2; i < num; ++i) {

            if (num % i == 0) {

                return false;

            }

        }

        return true;

    }

}

public class Main {

    public static void main(String[] args) {

        int choice, num1, num2;

        Scanner scan = new Scanner(System.in);

        Loops loop = new Loops();

        do {

            System.out.print(

                    "\n1. Print Numbers\n2.sum of numbers\n3.Print Multiplication Table\n4.Find factorial\n5.calculate power\n6.Reverse String\n7.check for even\n8.check for odd\n9.check for Prime\n0.Exit\nEnter choice : ");

            choice = scan.nextInt();

            switch (choice) {

                case 1: {

                    System.out.print("Enter value of low : ");

                    num1 = scan.nextInt();

                    System.out.print("Enter value of high : ");

                    num2 = scan.nextInt();

                    loop.printNumbers(num1, num2);

                    break;

                }

                case 2: {

                    System.out.print("Enter number : ");

                    num1 = scan.nextInt();

                    System.out.println(loop.sumOfNumbers(num1));

                    break;

                }

                case 3: {

                    System.out.print("Enter number : ");

                    num1 = scan.nextInt();

                    loop.printMultiplicationTable(num1);

                    break;

                }

                case 4: {

                    System.out.print("Enter number : ");

                    num1 = scan.nextInt();

                    loop.getFactorialOfNum(1);

                    break;

                }

                case 5: {

                    System.out.print("Enter number: ");

                    num1 = scan.nextInt();

                    System.out.print("Enter power : ");

                    num2 = scan.nextInt();

                    System.out.println(loop.pow(num1, num2));

                    break;

                }

                case 6: {

                    scan.nextLine();

                    System.out.print("Enter String : ");

                    String str = "";

                    str = scan.nextLine();

                    System.out.println(loop.reverseMyString(str));

                    break;

                }

                case 7: {

                    System.out.print("Enter number : ");

                    num1 = scan.nextInt();

                    System.out.println(loop.isEven(num1));

                    break;

                }

                case 8: {

                    System.out.print("Enter number : ");

                    num1 = scan.nextInt();

                    System.out.println(loop.isOdd(num1));

                    break;

                }

                case 9: {

                    System.out.print("Enter number : ");

                    num1 = scan.nextInt();

                    System.out.println(loop.isPrime(num1));

                    break;

                }

                case 0: {

                    System.out.println("Good Bye!");

                    break;

                }

                default: {

                    System.out.println("Invalid choice");

                }

            }

        } while (choice != 0);

        scan.close();

    }

}