Question

Follow exactly all the instructions provided below:

Do not deviate from the instructions provided below or add any unnecessary code to program.

Pay close attention to the directions! Make absolutely certain that you are doing exactly what the assignment asks you to do without any more code required.

Keep the program's code as simple as possible and begineer friendly level with no advanced level Java concepts/skills.

Write a program that asks the user for a number. The program should check the number to ensure that it is valid (if not, the user should enter a valid number to continue.) The program should print out all of the prime numbers from 2 up to the number, with up to 10 numbers per line. (Recall: A prime number is a number that is only divisible by itself and 1)The code should ask the user if they want to run the program again. You will need: 1. A scanner object to read 1. The user's numerical entry 2. The user's string response 2. Variables to store: 1. The user's entry (should be an integer) 2. The user's response (should be a string) 3. The number of primes (this will help to determine how many numbers are printed before moving to the next line) (Include additional variables as needed) 3. Several loops 1. A do...while loop to repeat the program. This loop will contain: 1. A while loop for input validation 2. A while loop to determine if the number is prime (this loop may contain a nested for loop to check primes from 2 up to the user's entry) An if statement to determine when to skip a line after 10 numbers has been printed 4. Lots of comments for documentation

Answer 1

PROGRAM:

import java.util.InputMismatchException;
import java.util.Scanner;

public class PrintPrimes {

   public static void main(String[] args) {
       //scanner object to read user data
       Scanner input=new Scanner(System.in);
      
       //variables to store
       int number; //variable to store the number
       String repeat=""; //variable to store whether user's wants to run the program or not
       int numOfPrimes=0; //variable to hold the count of primes
      
       //loop that repeats until user terminates the program
       do
       {
           //for each execution set numOfPrimes to 0
           numOfPrimes=0;
          
           //read the number until which user wants to print primes
           System.out.print("\nEnter a number: ");
          
           //to check if user input is valid or not place it in a try catch block
           try
           {
               //read the integer
               number=input.nextInt();
              
               System.out.print("\nPrime Numbers upto "+ number + " are: \n");

               //run a loop from 2 until the specified number is reached
               for(int i=2; i < number; i++)
               {
                   //declare a boolean variable that tells whether the number is prime or not
                   boolean isPrime = true;

                   //run a loop from 2 to i
                   for(int j=2; j < i ; j++)
                   {   
                       //check if i is divisible by any other number
                       if(i % j == 0)
                       {
                           //if divisible set is Prime to false and go to next number
                           isPrime = false;
                           break;
                       }
                   }
                   // print the number if its prime
                   if(isPrime)
                   {
                       System.out.print(i+" ");
                       numOfPrimes++; //increment the count of primes
                      
                       //if number of primes is divisible by 10 the break the line
                       if(numOfPrimes%10==0)
                           System.out.println();
                   }
               }
              
              
           }
           //catch the exception if user entered invalid input
           catch(InputMismatchException exception)
           {
           //if not a valid integer print error
           System.out.println("Invalid input. Try again...");
           }
          
           //ask if user wants to repeat the execution
           System.out.print("\n\nDo you want to run the program again (yes/no)? ");
           input.nextLine();
           //read the users choice
           repeat=input.nextLine();
          
       }while(repeat.toLowerCase().equals("yes")); //repeat the execution as long as user types yes
       System.out.print("\nProgram terminated..");
   }

}

OUTPUT:

Console terminated> PrintPrimes [Java Application] C:Program Files Javaljre1.8.0 73 Enter a number: 50 Prime Numbers upto 50 are: 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 Do you want to run the program again (yes/no)? yes Enter a number: 100 Prime Numbers upto 180 are: 2 3 57 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 Do you want to run the program again (yes/no)? no Program terminated..