import java.util.Queue;
import java.util.ArrayDeque;

// Stack: push/pop/peek/isEmpty/EmptyStackException
// Queue: add/remove/element/isEmpty/NoSuchElementException
public class Palindrome
{
   public static boolean isPalindrome(String s)
   {
      Stack<Character> stack = new CarlStack<Character>();
      Queue<Character> queue = new ArrayDeque<Character>();

      for (int i = 0; i < s.length(); i++)
      {
         char character = s.charAt(i);

         // ignore non-letter characters
         if (Character.isLetter(character))
         {
            // ignore upper/lower case differences
            character = Character.toLowerCase(character);
            stack.push(character);
            queue.add(character);
         }
      }

      while (!stack.isEmpty())
      {
         if (stack.pop() != queue.remove())
         {
            return false;
         }
      }
      return true;
   }

   public static void main(String[] args)
   {
      System.out.println(isPalindrome("racecar"));
      System.out.println(isPalindrome("tofu"));
      System.out.println(isPalindrome("Sit on a potato pan, Otis!"));
   }
}