JavaAlgorithms/Maths/PrimeCheck.java

package Maths;

import java.util.Scanner;

public class PrimeCheck {
  public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);

    System.out.print("Enter a number: ");
    int n = scanner.nextInt();
    if (isPrime(n)) {
      System.out.println(n + " is a prime number");
    } else {
      System.out.println(n + " is not a prime number");
    }
    scanner.close();
  }

  /***
   * Checks if a number is prime or not
   * @param n the number
   * @return {@code true} if {@code n} is prime
   */
  public static boolean isPrime(int n) {
    if (n == 2) {
      return true;
    }
    if (n < 2 || n % 2 == 0) {
      return false;
    }
    for (int i = 3, limit = (int) Math.sqrt(n); i <= limit; i += 2) {
      if (n % i == 0) {
        return false;
      }
    }
    return true;
  }
}