import javax.swing.JOptionPane;
public class StringRecursion
{
	public static void main(String[] args)
	{
		boolean done = false;
		do
		{
			String input = JOptionPane.showInputDialog(null, "Any String");
			
			if (input == null)
				done = true;
			else
				System.out.println(input + 
				                   (isPalindrome(input) ? " IS " : " IS NOT ")
										 + "a Palindrome" );
		} while (!done);
	}

	public static boolean isPalindrome(String str)
	{
		String testString = lettersOnly(str);
		return reverse(testString).equalsIgnoreCase(testString);
		
		//return symmetric( lettersOnly(str).toLowerCase() );
	}
		
	public static String reverse(String str)
	{
		if (str.length() <=1)
			return str;
			
		return reverse(str.substring(1)) + str.charAt(0);
	}
	
	public static String lettersOnly(String str)
	{
		if (str.length() == 0)
			return "";
		
		char firstChar = str.charAt(0);
      String remainder = lettersOnly( str.substring(1) );
		
		if ( !Character.isLetter( firstChar ) )
		   return remainder;	
         	
      return firstChar + remainder;
	}
		
	private static boolean symmetric(String str)
	{
		if (str.length() <= 1)
			return true;
		
      int endIndex = str.length()-1;
		if ( str.charAt(0) != str.charAt(endIndex) )
			return false;
			
		return symmetric( str.substring(1, endIndex) );
	}
}