import javax.swing.JOptionPane;
public class PalindromeTester
{
   //Process a series of input Strings
   //Report whether each String is a palindrome
	public static void main(String[] args)
	{
		String input;
		do
		{
			input = JOptionPane.showInputDialog(null, "Any String");
			
			if (input != null)
				System.out.println(input + " IS " 
				                 + (isPalindrome(input) ? "" : " NOT ")
									  + "a Palindrome" );
		} while (input != null);
	}

   //Return true iff parameter str is a Palindrome
	public static boolean isPalindrome(String str)
	{
		String testString = lettersOnly(str);
		return reverse(testString).equalsIgnoreCase(testString);

		//return isSymmetric( lettersOnly(str).toLowerCase() );
	}
	
   //Return a String containing only the letters of the parameter
   // in the same order as they occur in the parameter
	public static String lettersOnly(String str)
	{
		if (str.length() == 0)
			return "";
		
		char firstChar = str.charAt(0);
      String remainder = str.substring(1) ;
      
      return (Character.isLetter(firstChar) ? firstChar : "") + 
             lettersOnly( remainder );
	}
   
   //Return a String which is the reverse of the parameter 	
	public static String reverse(String str)
	{
		if (str.length() <=1)
			return str;
			
		return reverse(str.substring(1)) + str.charAt(0);
	}
   
   //Return true iff the parameter str reads the same
   // backwards as forwards	
	private static boolean isSymmetric(String str)
	{
		if (str.length() <= 1)
			return true;
		
      int endIndex = str.length()-1;
		if ( str.charAt(0) != str.charAt(endIndex) )
			return false;
			
		return isSymmetric( str.substring(1, endIndex) );
	}
}