I really can't understand how this recursive works??

Question

Hi all,
I have got a recursive function that checks for palendrome string. But it is confusing. I know that a string is palenromme if it is empty or has a char or first char and last one are same and middle is palindromme too.
but can't understand how this function works.
class Palindromme
     boolean palindrom(String s)
          if (s.length() <= 1 || s.equals(null) || s=="") //this is the stopping point
               return true;
          else
          {                    //recursive definition
               return ( s.charAt(0) == s.charAt(s.length()-1) ) && palindrom(s.substring(1,s.length()-1));
specially i don't know how palindrom(s.substring(1,s.length()-1)); is working cause it has to be increased for each loop.
abdul
PS: actually i don't know how recursion works from Data structure point of view

Answer 1

Hi,
ok your palindrome is : "otto"
return ( s.charAt(0) == s.charAt(s.length()-1) ) && palindrom(s.substring(1,s.length()-1));
              o                     o                                   tt
so first part is true                                        
in the second part palindrom is called again but with the remaining tt
so second time :
return ( s.charAt(0) == s.charAt(s.length()-1) ) && palindrom(s.substring(1,s.length()-1));
               t                     t                                 ""
Third time:
if (s.length() <= 1 || s.equals(null) || s=="") //this is the stopping point
return true;after all for otto the recusion is:
return ( s.charAt(0) == s.charAt(s.length()-1) ) && s.charAt(1) == s.charAt(s.length()-2) ) && nothing left of otto);
Phil