How to Check if a Number is a Palindrome in Java – Step-by-Step Guide with Code

🧠 What is a Palindrome Number?

A palindrome number is a number that reads the same backward as forward.

Examples:

• 121 is a palindrome (reads same from left to right and right to left)

• 123 is not a palindrome

• 1221 is a palindrome

💻 Java Code to Check Palindrome Number

Let’s start with a simple Java program to check if a number is a palindrome:

import java.util.Scanner;

public class PalindromeChecker {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        // Step 1: Take input from user
        System.out.print("Enter a number: ");
        int number = scanner.nextInt();

        // Step 2: Store original number for comparison later
        int originalNumber = number;
        int reversedNumber = 0;

        // Step 3: Reverse the number
        while (number != 0) {
            int digit = number % 10;           // Get the last digit
            reversedNumber = reversedNumber * 10 + digit; // Build reversed number
            number = number / 10;              // Remove last digit
        }

        // Step 4: Compare original and reversed numbers
        if (originalNumber == reversedNumber) {
            System.out.println(originalNumber + " is a palindrome.");
        } else {
            System.out.println(originalNumber + " is not a palindrome.");
        }

        scanner.close();
    }
}

🪜 Step-by-Step Explanation

✅ Step 1: Taking User Input

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

• We use the Scanner class to take input from the user.

• The number entered by the user is stored in a variable called number.

✅ Step 2: Store the Original Number

int originalNumber = number;

• We store the original number in another variable so that we can compare it later with the reversed number.

✅ Step 3: Reverse the Number

int reversedNumber = 0;

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

Let’s break this loop down:

• number % 10 gets the last digit of the number.

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  Multiply reversedNumber by 10 to shift digits to the left and add the new digit.

• Divide number by 10 to remove the last digit (since it's already used).

Example:
If the user enters 12321:

• First digit: 1

• Second digit: 2

• ...

• Eventually reversedNumber will become 12321 again.

✅ Step 4: Compare and Print Result

if (originalNumber == reversedNumber) {
    System.out.println(originalNumber + " is a palindrome.");
} else {
    System.out.println(originalNumber + " is not a palindrome.");
}

• We check if the reversed number is equal to the original number.

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  If yes, it's a palindrome.

• If not, it's not a palindrome.

🔄 Sample Outputs

Enter a number: 1221
1221 is a palindrome.

Enter a number: 456
456 is not a palindrome.

🧪 Edge Case: What if Number is Negative?

Negative numbers are not palindromes because they include a minus sign -, which cannot appear at the end when reversed.

You can handle this in your code:

if (originalNumber < 0) {
    System.out.println("Negative numbers are not considered palindromes.");
}

🛠️ Tips for Beginners

• Understand how the while loop works with % and /.

• Practice the same logic with strings later (for word palindromes).

• Test with different inputs like 0, single digits, even and odd-length numbers.

✅ Conclusion

Checking whether a number is a palindrome in Java is a great beginner-level programming problem. It helps you understand loops, mathematical operations, and logic building.

With the code and step-by-step explanation above, you should now be able to write and understand a palindrome number checker with confidence!