public class Palindrome4
{
   public static void main(String[] args)
   {
      String  s = "racecar";
      boolean ans;

      ans = isPalindrome(s);
   }
   
   public static boolean isPalindrome(String w)
   {
       int lastPos = w.length() - 1;
       
       return isPalindrome(w, 0, lastPos);
   }
   
   public static boolean isPalindrome(String w, int startPos, int endPos)
   {
      if ( startPos >= endPos )
      {  // base cases
         return true;
      }
      else
      {
         boolean helpSol = isPalindrome(w, startPos+1, endPos-1);
         
         return  (w.charAt(startPos) == w.charAt(endPos)) && helpSol;
      }
   } 
}