Example: PalindromeCheckTwoPointer in Java

// PalindromeCheckTwoPointer
import java.util.Scanner;

public class Main {

    // Helper method to preprocess the string
    private static String preprocessString(String s) {
        StringBuilder cleanedString = new StringBuilder();
        for (char c : s.toCharArray()) {
            if (Character.isLetterOrDigit(c)) {
                cleanedString.append(Character.toLowerCase(c));
            }
        }
        return cleanedString.toString();
    }

    // Method to check for palindrome using two pointers
    public static boolean isPalindromeTwoPointer(String s) {
        String cleaned = preprocessString(s);
        int left = 0;
        int right = cleaned.length() - 1;

        while (left < right) {
            if (cleaned.charAt(left) != cleaned.charAt(right)) {
                return false; // Mismatch found
            }
            left++;
            right--;
        }
        return true; // No mismatch found
    }

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

        // Step 1: Get input string from the user
        System.out.print("Enter a string to check for palindrome: ");
        String inputString = scanner.nextLine();

        // Step 2: Check if it's a palindrome using the two-pointer method
        if (isPalindromeTwoPointer(inputString)) {
            System.out.println("'" + inputString + "' is a palindrome (Two-Pointer Method).");
        } else {
            System.out.println("'" + inputString + "' is NOT a palindrome (Two-Pointer Method).");
        }

        scanner.close();
    }
}