Prime Check
Check whether a given number is prime using a loop.
IntermediateTopic: Module 3: Loop Programs
Java Prime Check Program
This program helps you to learn the fundamental structure and syntax of Java programming.
import java.util.Scanner;
public class Main {
private static boolean isPrime(int n) {
if (n <= 1) return false;
if (n == 2) return true;
if (n % 2 == 0) return false;
for (int i = 3; i * i <= n; i += 2) {
if (n % i == 0) return false;
}
return true;
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number: ");
int n = sc.nextInt();
if (isPrime(n)) {
System.out.println(n + " is Prime");
} else {
System.out.println(n + " is not Prime");
}
sc.close();
}
}Output
Enter a number: 29 29 is Prime
Understanding Prime Check
We check divisibility up to √n to decide if the number is prime.
Note: To write and run Java programs, you need to set up the local environment on your computer. Refer to the complete article Setting up Java Development Environment. If you do not want to set up the local environment on your computer, you can also use online IDE to write and run your Java programs.