Question

Task 5.2 Numerical Analysis Using Nested Loops (13 pts)

Consider the following program:

void setup()
{

//Read a positive integer from the user

//Your code starts here }

Complete this program such that it calculates all prime numbers between 1 and the value that is assigned to variable num and outputs them on the screen. A prime number is a positive integer that has no other factors other than itself and 1. You should use a nested loop, i.e., write code where a for loop runs within another for loop. DO NOT USE CLASSES/OBJECTS, METHODS, OR APPLETS; simply use a nested loop.

The program should print prime numbers in reverse order, i.e., starting with the largest one.

Example: When num = 10, the program should print: 7 5 3 2 , which are the prime numbers between 1 and 10.

Example: When num = 19, the program should print 17 13 11 7 5 3 , which are the prime numbers between 1 and 19.

HINT: If you are having problems with this task, start by writing a for loop to check if a number is prime or not. Once this is complete, nest this loop within another loop to check all numbers in the range given by the user.

___________________________________________________________________________________________________________________________________________________

This is the code that I've written in attempting this problem. Please modify it and make any appropriate changes. The idea behind my code is that since the numbers have to be printed in reverse order, I've initialized i in the outer loop to equal num and then I have a decrementing expression so that it can detect, store, and then print all the prime numbers between 1 and num in reverse order. Note: I am very new to processing (I only started learning it 3 weeks ago, so please don't go beyond the scope of what I've learnt (which is strings/chars, if/else decision structures, and loops).

void setup(){
import javax.swing.JOptionPane;
int num;
num=parseInt(JOptionPane.showInputDialog("Enter a positive, real integer"));
int i;
int j;

for (i = num; i > 1; i--){
for (j = 2; j < i; j++){
if (i%j == 0)
{
break;
}
}
if (i==j)
{
print(num);
}
}
println();
}

Answer 1

Note: Could you plz go through this code and let me know if u need any changes in this.Thank You
_________________

// PrimeNos.java

import java.util.Scanner;

public class PrimeNos {

   public static void main(String[] args) {
setUp();

   }

   private static void setUp() {
/*
* Creating an Scanner class object which is used to get the inputs
* entered by the user
*/
Scanner sc = new Scanner(System.in);
int num;
while(true)
{
System.out.print("Enter Number :");
num=sc.nextInt();
if(num>0)
{
break;
}
else
{
System.out.println("** Invalid.Must be positive number **");
}
}
  
int i=num;
for(i=num;i>0;i--)
{
int flag = 0;
int j = 2;
for(j=2;j < i;j++)
{
if (i % j == 0)
{
flag = 1;
}
}
if (flag == 0 && i!=1)
{
System.out.print(i+" ");
}
  
}

      
   }

}
________________________

Output:

Enter Number :50
47 43 41 37 31 29 23 19 17 13 11 7 5 3 2

________________________Thank You