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Java Program to Check Palindrome Number

Learn how to check if a number is a palindrome in Java using digit reversal and string comparison methods with clear examples.

A palindrome number reads the same forwards and backwards (e.g., 121, 1331, 7). In this article, we'll implement two approaches to check if a number is a palindrome:

  • Reverse the number and compare with original
  • Convert to string and compare with its reverse

Before you start, you may want to review:

1) Mathematical Approach (Reverse Number)

This method reverses the number mathematically by extracting digits.

Example

class Main {
  public static void main(String[] args) {
    int num = 121; // change value to test

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



  static boolean isPalindrome(int num) {
    int original = num;
    int reversed = 0;

    // Handle negative numbers
    if (num < 0) return false;

    // Reverse the number
    while (num > 0) {
      int digit = num % 10;
      reversed = reversed * 10 + digit;
      num /= 10;
    }

    return original == reversed;
  }
}

Output (for num = 121)

121 is a palindrome number.

2) String Comparison Approach

Convert the number to string and compare with its reverse.

Example

class Main {
  public static void main(String[] args) {
    int num = 1234; // change value to test

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



  static boolean isPalindromeString(int num) {
    // Handle negative numbers
    if (num < 0) return false;

    String original = String.valueOf(num);
    String reversed = new StringBuilder(original).reverse().toString();

    return original.equals(reversed);
  }
}

Output (for num = 1234)

1234 is not a palindrome number.

3) Interactive Program

A complete program that takes user input and tests multiple numbers.

Example

import java.util.Scanner;

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

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

    System.out.println("\nChecking " + num + "...");

    // Method 1: Mathematical approach
    boolean result1 = isPalindromeMath(num);
    System.out.println("Mathematical method: " + (result1 ? "Palindrome" : "Not palindrome"));

    // Method 2: String approach
    boolean result2 = isPalindromeString(num);
    System.out.println("String method: " + (result2 ? "Palindrome" : "Not palindrome"));

    scanner.close();
  }



  static boolean isPalindromeMath(int num) {
    if (num < 0) return false;
    int original = num, reversed = 0;
    while (num > 0) {
      reversed = reversed * 10 + num % 10;
      num /= 10;
    }
    return original == reversed;
  }

  static boolean isPalindromeString(int num) {
    if (num < 0) return false;
    String str = String.valueOf(num);
    return str.equals(new StringBuilder(str).reverse().toString());
  }
}

Sample Output

Enter a number to check: 12321

Checking 12321...
Mathematical method: Palindrome
String method: Palindrome

Notes & Tips

  • Performance: Mathematical approach is generally faster as it avoids string operations
  • Edge cases: Negative numbers are typically not considered palindromes
  • Common palindromes: 0, 1, 11, 22, 101, 121, 131, 1001, 1221, etc.
  • Memory: Mathematical approach uses O(1) space, string approach uses O(log n) space