PalindromeChecker.java

import java.util.Scanner;

public class PalindromeChecker {
    public static boolean isPalindrome(String str) {
        // Remove non-alphanumeric characters and convert to lowercase
        str = str.replaceAll("[^a-zA-Z0-9]", "").toLowerCase();
        
        // Check if the string is equal to its reverse
        int left = 0, right = str.length() - 1;
        while (left < right) {
            if (str.charAt(left) != str.charAt(right)) {
                return false;
            }
            left++;
            right--;
        }
        return true;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a word or phrase: ");
        String input = scanner.nextLine();
        
        if (isPalindrome(input)) {
            System.out.println("It's a palindrome!");
        } else {
            System.out.println("It's not a palindrome.");
        }
        scanner.close();
    }
}