Prime Number Check in Java: Explanation & Practice

Problem summary

Write a program that checks if a given number is prime. Your code should work for ANY positive integer.

Starter code

public class Main {
    public static void main(String[] args) {
        int number = 17; // Test case 1
        
        // Check if number is prime
        // Print: Is prime: <true/false>
    }
}

Expected output and test cases

• 17 is prime

  Is prime: true

• 18 is not prime

  Is prime: false

• 1 is not prime

  Is prime: false

Hints

1. A prime has exactly 2 factors: 1 and itself
2. Check divisibility from 2 to sqrt(n)
3. 1 is NOT a prime number

Related Control Flow exercises

• Practice Print Even Numbers in Java
• Practice Multiplication Table in Java
• Practice Nth Fibonacci Number in Java

Practice all Control Flow exercises · Run this idea in the Java compiler