Java program to check the given number is prime or not.

package com.dev.test;

import java.util.Scanner;

public class PrimeNumber {

    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        System.out.print("Enter number : ");
        while (in.hasNext()){
            int num = in.nextInt();
            if (isPrime(num)) {
                System.out.println(num + " is prime number");
            } else {
                System.out.println(num + " is not a prime number");
            }
            System.out.print("Enter number : ");
        }
    }

     public static boolean isPrime(int num) {
        //check if n is 2
        if (num == 2){
            return true;
        }
        //check if n is a multiple of 2
        if (num % 2 == 0){
            return false;
        }
        //if not, then just check the odds
        for (int i = 3; i * i <= num; i += 2) {
            if (num % i == 0)
                return false;
        }
        return true;
    }
}