Prime Number in Java | Spring Java Lab

Prime Number in Java

A prime number is a number greater than 1 that has no divisors other than 1 and itself.

Examples: 2, 3, 5, 7, 11, 13...

Java Program to Check Prime Number

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 number = scanner.nextInt();

        if (number <= 1) {
            System.out.println(number + " is not a prime number.");
            return;
        }

        boolean isPrime = true;
        for (int i = 2; i <= number / 2; i++) {
            if (number % i == 0) {
                isPrime = false;
                break;
            }
        }

        if (isPrime) {
            System.out.println(number + " is a prime number.");
        } else {
            System.out.println(number + " is not a prime number.");
        }
    }
}

Output

Enter a number: 7  
7 is a prime number.

Explanation

  • We check if the number is divisible by any number between 2 and half of the number.
  • If divisible, it's not a prime.
  • We exclude 0 and 1 since they are not prime numbers.

Conclusion

This is a basic and frequently asked question in Java interviews, suitable for understanding loops and conditions.