Problem 2 - Prime Numbers

🎯 Overview

Prime numbers are numbers that are greater than 1 which have only have two factors: 1 and the number itself.

Important concepts to be aware of:

• For a number N, it can only be divisible completely by N/2. For numbers greater than N/2, it cannot divide N completely.
• For a number N, it will have divisors(if completely divisible) which will be less than or equal to square root of N.

🎯 Solving the problem in Java

Problem Statement: Write a Java program to check if a given number is prime or not.

/**
 * Problem 2: Write a Java program to check if a given number is prime or not
 */
public class Problem_2 {

  public static void main(String[] args) {

    System.out.println("Enter the value for n:");
    Scanner sc = new Scanner(System.in);

    int n = sc.nextInt();

    if (n <= 1) {
      System.out.println("Not Prime");
      System.exit(0);
    }

    for (int i = 2; i <= n / 2; i++) {
      if (n % i == 0) {
        System.out.println("Not Prime");
        System.exit(0);
      }
    }

    System.out.println("Prime");
  }
}

Output:

Enter the value for n:
33
Not Prime

Process finished with exit code 0

Enter the value for n:
11
Prime

Process finished with exit code 0

🎯 Github

Code shared in this post can be found here.