🚀 Programming Example

Java Program - Check if a Number is Prime

👁 220 Views

💻 Practical Program

📘 Step Learning

A basic program to determine if a given number is a prime number.

📌 Information & Algorithm

This Java program checks whether a given number (in this case, 29) is a prime number. It initializes a boolean variable isPrime to true and uses a for loop to iterate from 2 to number / 2. If the number is divisible by any value in this range (number % i == 0), it sets isPrime to false and breaks out of the loop. After the loop, it prints whether the number is prime based on the value of isPrime. If isPrime remains true, the number is prime; otherwise, it is not.

Given Input:

Expected Output:


29 is a prime number.

💻 Program Code

public class PrimeCheck {
    public static void main(String[] args) {
        int number = 29;
        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.");
    }
}

🖥 Program Output

29 is a prime number.

📘 Explanation

check if any number is prime, allowing the user to input the 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();
        boolean isPrime = true;

        if (number <= 1) {
            isPrime = false;
        } else {
            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.");
    }
}

Explanation:

Importing Scanner: Imports the Scanner class to read user input.
Creating a Scanner Object: Scanner scanner = new Scanner(System.in); creates a Scanner object to read input from the console.
Reading User Input: int number = scanner.nextInt(); reads an integer input from the user.
Prime Check Logic: The code remains largely the same, but now it checks the user-provided number instead of a hardcoded value.
Edge Case Handling: Added a condition to handle numbers less than or equal to 1, which are not prime.

🎯 How to learn from this example

First understand the algorithm carefully. Then study the program line-by-line and compare it with the output. Finally, review the explanation section to strengthen your logic and programming understanding.

🔥 Practice suggestion

Rewrite the program without looking at the code. Modify values, conditions or logic and run it again. This helps improve confidence and strengthens coding skills much faster.