Prime Number Program in Java Using Scanner Example.

Suppose, the value entered is say 121. It is assigned to an integer variable num. Now, num is divided by all the numbers from 2 to 8 (because a number can be divided by 1 and itself) (% rehrrns remainder). If the number is divided by any number from 2 to 8, its remainder will come to be 0 and in that case the message “Number is not prime” is displayed on the screen. 121 is not divisible by 2 but is no doubt divisible by 3 which returns remainder as 0 and hence it is not a prime number.

Algorithm For Prime Number Program:

step 1: Read num

step 2: Set b=l, c=0

step 3: Repeat through step-5 while (b <= num)

step 4: If (num mod b) equals to 0 then set c = c + 1

step 5: b = b + l

step 6: If c equals to 2 then print “num is prime”

Else print “num is not prime”

step 7: Exit

Here is the Java Example for Prime Number Program:

import java.util.Scanner; 
 public class PrimeNumber 
 { 
                 public static void main(String args[]) 
              { 
                   int num,b,c; 
                   Scanner s=new Scanner(System.in); 
                   System.out.println("Enter A Number"); 
                   num =s.nextInt(); 
                   b=1; 
                   c=0; 
                    while(b<= num) 
                       { 
                           if((num%b)==0) 
                              c=c+1; 
                              b++; 
                       } 
                        if(c==2) 
                        System.out.println(num +" is a prime number"); 
                        else 
                        System.out.println(num +" is not a prime number"); 
              } 
 }