Java program to check if a number is a palindrome

Java program to check if a number is a palindrome:- A palindrome is a number (or a word, phrase, or sequence) that reads the same forward and backward. For example, 121, 1331, and 12321 are palindrome numbers. Checking if a number is a palindrome is a common programming exercise that involves reversing the number and comparing it with the original.

Java Program to Check if a Number is a Palindrome

Here’s a Java program that prompts the user to enter a number and then checks if that number is a palindrome.

import java.util.Scanner;

public class PalindromeCheck {
    public static void main(String[] args) {
        // Create a Scanner object to read input from the user
        Scanner scanner = new Scanner(System.in);

        // Prompt the user to enter a number
        System.out.print("Enter a number: ");
        int number = scanner.nextInt();

        // Check if the number is a palindrome
        boolean isPalindrome = isPalindrome(number);

        // Print the result
        if (isPalindrome) {
            System.out.println(number + " is a palindrome.");
        } else {
            System.out.println(number + " is not a palindrome.");
        }
    }

    // Method to check if a number is a palindrome
    public static boolean isPalindrome(int n) {
        int originalNumber = n;
        int reversedNumber = 0;

        // Reverse the number
        while (n != 0) {
            int digit = n % 10;
            reversedNumber = reversedNumber * 10 + digit;
            n /= 10;
        }

        // Compare the original number with the reversed number
        return originalNumber == reversedNumber;
    }
}

Explanation of the Code: (Java program to check if a number is a palindrome)

Let’s break down the program step-by-step to understand how it works.

Importing the Scanner Class: We import the Scanner class from the java.util package to read input from the user.

import java.util.Scanner;

2. Creating the Main Class: We create a public class named PalindromeCheck. In Java, the class name should match the filename.

public class PalindromeCheck {

3. Main Method: The main method is the entry point of the program. Inside this method, we will write the code to check if a number is a palindrome.

public static void main(String[] args) {

4. Creating a Scanner Object: We create a Scanner object to read input from the user.

Scanner scanner = new Scanner(System.in);

5. Reading Input from the User: We prompt the user to enter a number and store this value in a variable.

System.out.print("Enter a number: ");
int number = scanner.nextInt();

6. Checking if the Number is a Palindrome: We call the isPalindrome method to check if the number is a palindrome. The result is stored in a boolean variable isPalindrome.

boolean isPalindrome = isPalindrome(number);

7. Printing the Result: We print whether the number is a palindrome based on the value of isPalindrome.

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

8. Method to Check if a Number is a Palindrome: The isPalindrome method reverses the number and compares it with the original number. If they are the same, the number is a palindrome.

public static boolean isPalindrome(int n) {
    int originalNumber = n;
    int reversedNumber = 0;

    // Reverse the number
    while (n != 0) {
        int digit = n % 10;
        reversedNumber = reversedNumber * 10 + digit;
        n /= 10;
    }

    // Compare the original number with the reversed number
    return originalNumber == reversedNumber;
}

Explanation of the `isPalindrome` Method

Storing the Original Number: We store the original number in a variable originalNumber.

int originalNumber = n;

4. Reversing the Number: We initialize a variable reversedNumber to 0. We use a while loop to reverse the digits of the number. In each iteration, we extract the last digit of the number using n % 10, add it to reversedNumber, and then remove the last digit from n by dividing it by 10.

int reversedNumber = 0;

while (n != 0) {
    int digit = n % 10;
    reversedNumber = reversedNumber * 10 + digit;
    n /= 10;
}

3. Comparing the Original and Reversed Numbers: We compare the original number with the reversed number. If they are equal, the number is a palindrome, and we return true. Otherwise, we return false.

return originalNumber == reversedNumber;

Running the Program

To run the program, follow these steps:

Save the code in a file named PalindromeCheck.java.
Open a command prompt or terminal and navigate to the directory where you saved the file.
Compile the program using the following command:

javac PalindromeCheck.java

4. Run the compiled program using the following command:

java PalindromeCheck

Follow the prompt to enter a number. The program will display whether the number is a palindrome or not.

Example Output

If you run the program and enter 121 as the number, the output will be:

Enter a number: 123
123 is not a palindrome.

What did we learn from this article?

Checking if a number is a palindrome is a fundamental exercise that helps in understanding loops and conditional statements in programming. This Java program demonstrates how to implement a palindrome check by reversing a number and comparing it with the original. By practicing such basic programs, you can strengthen your problem-solving skills and gain confidence in your ability to write efficient Java code. Keep practicing and exploring more problems to enhance your programming skills.

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