Web Development

Palindrome in Java

Last Updated: 15th August, 2024

Jay Abhani

Senior Web Development Instructor at almaBetter

Learn how to implement a Palindrome in Java with multiple solutions and step-by-step explanations in this guide. Ideal for beginners and experienced developers

The concept of palindrome numbers is a fundamental programming challenge that every Java developer encounters. It is not only a popular topic in coding interviews but also serves as an excellent exercise to understand basic algorithms, loops, conditionals, and number manipulations. This article provides an in-depth exploration of the palindrome number program in Java, covering multiple approaches, optimizations, and edge cases.

Throughout this article, you will see various implementations of the palindrome number in Java, learn about different ways to solve the problem, and understand the underlying principles that make these solutions effective.

What is a Palindrome Number in Java?

A palindrome number is a number that remains the same when its digits are reversed. For example:

121 is a palindrome because reversing it gives 121.

123 is not a palindrome because reversing it gives 321.

In simpler terms, a palindrome number is symmetric and reads the same forward and backward. The task of writing a palindrome java program involves checking if a given number possesses this symmetry.

Basic Approach to Palindrome Number Program in Java

Let’s start with the most straightforward approach to solving this problem: reversing the number and comparing it with the original number.

Step-by-Step Implementation

1. Input the Number: We first need to accept the number from the user or define it in the program.

2. Reverse the Number: Reverse the digits of the number.

3. Compare the Original and Reversed Numbers: If they are the same, the number is a palindrome.

4. Output the Result: Display whether the number is a palindrome or not.

Code for the Basic Palindrome Program in Java:

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Detailed Explanation of the Basic Palindrome Code in Java:

Reversing the Number: The logic to reverse the number involves extracting digits one by one (using modulus operator) and constructing the reversed number by appending these digits (by multiplying the reversed number by 10 and adding the extracted digit).

Comparison: After the reversal, we simply compare the reversed number with the original number. If they match, the number is a palindrome.

This approach is simple and works effectively for most cases, but it may not be the most efficient, especially for large numbers. Next, we’ll look at more advanced techniques to improve performance and handle edge cases better.

Optimized Approach: Checking Digits from Both Ends

Instead of reversing the entire number, another way to solve the problem is by comparing digits from both ends. This method is often more efficient because it doesn't require additional space for the reversed number.

Implementation

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Handling Edge Cases: We first check for numbers that are clearly not palindromes, such as negative numbers and numbers that end in zero (except zero itself).

Reversing Half of the Number: Instead of reversing the entire number, we reverse only the second half. The loop continues until the original number becomes less than or equal to the reversed half.

Final Comparison: After the loop, we check if the original number equals the reversed half or if the original number equals the reversed half divided by 10 (to handle odd-digit numbers). This approach reduces the space complexity and improves performance, especially for large numbers.

Read our latest articles “Features of Java” and “Dynamic Binding in Java

Recursive Approach to Palindrome Number in Java

Recursion is another interesting way to solve the palindrome number java problem. By using a helper function, we can recursively check if the number is a palindrome by comparing digits from both ends.

Recursive Implementation

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Base Case: The recursion stops when the original number becomes zero. At this point, the reversed number has been fully constructed.

Recursive Step: In each step, the function extracts the last digit, appends it to the reversed number, and then calls itself with the remaining digits.

Comparison: The final comparison checks whether the reversed number matches the original number.

This recursive method is elegant but may not be as efficient as the iterative solutions, especially when dealing with very large numbers, due to potential stack overflow issues.

Using String Conversion to Check Palindrome in Java

Another way to solve the problem is by converting the number to a string and then checking if the string is a palindrome. This approach leverages Java’s string manipulation capabilities, making the solution both simple and intuitive.

Implementation

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String Conversion: The number is first converted to a string using `Integer.toString(number)`.

Character Comparison: We then iterate through the string, comparing characters from both ends. If all corresponding characters match, the number is a palindrome.

This approach is straightforward and easy to understand, but it might not be as efficient as the purely numerical methods due to the overhead of string manipulation.

Common Mistakes in Writing Palindrome Number Programs in Java

When developing a java program for palindrome, several common mistakes can arise:

1. Ignoring Negative Numbers: Negative numbers should not be considered palindromes since the negative sign would disrupt the symmetry.

2. Overflow Issues: When reversing large numbers, there’s a risk of integer overflow. This needs to be managed carefully, especially in languages with fixed-width integers like Java.

3. Incorrect Handling of Edge Cases: Numbers like 10, 100, etc., which are not palindromes, may be mistakenly identified as such if edge cases are not handled correctly.

Performance Considerations

When choosing an approach to implement a palindrome number java program, it’s essential to consider the performance implications:

Time Complexity: The basic approach of reversing the number has a time complexity of O(n), where n is the number of digits. The optimized approach also runs in O(n) time but with reduced space complexity.

Space Complexity: The space complexity of the iterative approach is O(1), while the recursive approach might consume more memory due to the call stack.

For most practical purposes, the iterative approach with reversing half of the number strikes the best balance between simplicity and efficiency.

Conclusion

Writing a palindrome number program in Java is an excellent way to reinforce your understanding of loops, conditionals, and number manipulation techniques. Whether you're using a basic approach, an optimized method, recursion, or string conversion, each technique provides valuable insights into different ways of solving the problem.

This article explored multiple methods to check palindrome in Java, discussed common pitfalls, and provided various implementations to suit different scenarios. Understanding these approaches will help you write more efficient and robust code in your programming journey.

Whether you're preparing for interviews, working on projects, or learning programming concepts, mastering the palindrome code in Java is an essential skill that will serve you well. Join our comprehensive Full Stack Developer Course, where you can learn in-demand skills and only pay after placement. Start your journey to a successful tech career today!

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