In the following question, we are supposed to write a Java Source Code to ask the user for an Integer input and check if the number is a Prime Number.

Prime number are those numbers who have only two factors: 1 and the number itself.

Example: 1,2,3,5,7,11,13,etc are some examples of Prime Number.

The standard algorithm will be:

  1. Enter and Store the Integer Input from the user.
  2. Run a For-Loop from 1 to N.
  3. At every iteration of the loop, check if the value of the iteration completely divides the integer input.
  4. If the result is true, the counter variable is incremented.
  5. After the loop terminates, check if the value of the counter variable is 2 or not, which means there are only two factors for the N.
  6. Print the Result accordingly.

Source Code:

/* Program to check if a number is Prime or Not*/
import java.util.*;
class PrimeNumber
{
public static void main()
{
Scanner inp=new Scanner(System.in);
System.out.print("\n Enter Number: ");
int n=inp.nextInt();
int i,c=0;

for(i=1;i<=n;i++)
{
if(n%i==0)       //Checking if there are two factors of the number.
c++;
}

if(c==2)
System.out.println(n+" is a Prime Number");
else
System.out.println(n+" is not a Prime Number");

}
}

Output:

Enter Number: 2
2 is a Prime Number

 Enter Number: 36
36 is not a Prime Number

 Enter Number: 101
101 is a Prime Number

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