Java program to check prime number

The number which is only divisible by itself and 1 is known as prime number, for example 7 is a prime number because it is only divisible by itself and 1.

Example: Program to check whether input number is prime or not

To understand this program you should have the knowledge of for loop, if-else statements and break statement.

import java.util.Scanner;
class PrimeCheck
{
   public static void main(String args[])
   {		
	int temp;
	boolean isPrime=true;
	Scanner scan= new Scanner(System.in);
	System.out.println("Enter any number:");
	//capture the input in an integer
	int num=scan.nextInt();
        scan.close();
	for(int i=2;i<=num/2;i++)
	{
           temp=num%i;
	   if(temp==0)
	   {
	      isPrime=false;
	      break;
	   }
	}
	//If isPrime is true then the number is prime else not
	if(isPrime)
	   System.out.println(num + " is a Prime Number");
	else
	   System.out.println(num + " is not a Prime Number");
   }
}

Output:

Enter any number:
19
19 is a Prime Number

Output 2:

Enter any number:
6
6 is not a Prime Number

You can also use while loop to check the prime number:
Just replace this part of the code in above program:

for(int i=2;i<=num/2;i++)
{
   temp=num%i;
   if(temp==0)
   {
      isPrime=false;
      break;
   }
}

with this:

int i=2;
while(i<= num/2)
{
   if(num % i == 0)
   {
	isPrime = false;
	break;
   }
   i++;
}