Find Number is Prime or Not using Java Program

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What is Prime Number?

A prime number is a positive integer which is divisible by itself and only 1

Steps to check prime number

1. Accept the number from user ans store it into the n variable
2. Start the loop from 2 and check number n is divisible by loop variable or not.
3. if by any of the number the n is divisible, then update flag value to 1 and stop the loop.
4. check if flag = 1 then display number is not prime.
5. check if flag = 0 then display number is prime.

See the following flowchart to clearly understand the working of loop to find out number is prime or not.

Flowchart

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Example - Program to check given number is prime or not

import java.util.Scanner;
public class PrimeNumberEx 
{
	public static void main(String[] args) 
	{
		Scanner scan = new Scanner(System.in);
		int n,i,flag;
		i = 2; flag = 0;
		System.out.print("Enter any number : ");
		n = scan.nextInt();
		
		while(i<=n/2)
		{
			if(n%i == 0)
			{
				flag = 1;
				break;
			}
			i = i + 1; // or i += 1;
		}
		if(flag==0)
			System.out.print(n+" is a prime number");
		else
			System.out.print(n+" is Not prime number");
	}
}

Output