string.length not working properly in java

Question

Hi I have a code that checks if a string is palindrome or not.the code is like this:

         package ProjeTarahi;

         import java.util.*;
         import java.io.File;
         import java.io.FileInputStream;
         import java.io.FileNotFoundException;
         import java.util.Scanner;
         import java.util.logging.Level;
         import java.util.logging.Logger;
         import java.lang.String;

         public class Main 
         {

         public boolean CheckIsSymmetric(String s)
            {
               if (s.length()<=1) 
               {
                   return true;

                }

        if (s.charAt(0)==s.charAt(s.length()-1))
        {
            String sub = s.substring(1,s.length()-2);
            return CheckIsSymmetric(sub);
        }
        else
        {
            return false;
        }


    }

    public static void main(String args[])throws FileNotFoundException
    {
        Scanner sc=new Scanner(new FileInputStream(new File("in.txt")));
        String input=sc.nextLine();
        Main p=new Main();

        if(p.CheckIsSymmetric(input)==true)
        {
            System.out.println("in reshte motegharen ast");
        }
        else 
        {
            System.out.println("infinite");
        }

    }
}

I have written a code in c# that is exactly the same as the code above and its working very well but its not working properly in java and its output is always infinite. I stepped over my code and i think the problem is in the first if-statement of the CheckSymmetric() and it always jumps it but i don't know why.anybody can help me plz?

Answer 1

Surprisingly this type of question appear a lot in Computer-Science related classes. Here is my version of finding palindrome of a String. This version is design to strip away any non-word characters and reduce every character to lower case. It also work with numbers as it will just compare it as a String. It's only 13 lines long with a main and a Boolean method. No for loop, substring or anything.

Hope I help! -Cheers

p/s: I apologize for my style of indentation :D

import java.util.Scanner;
public class Palindrome  {
   public static void main(String[]args){
      if(isReverse()){System.out.println("This is a palindrome.");}
      else{System.out.print("This is not a palindrome");}
   }
   public static boolean isReverse(){
     Scanner keyboard =  new Scanner(System.in);
      System.out.print("Please type something: "); 
      String line = ((keyboard.nextLine()).toLowerCase()).replaceAll("\\W","");
      return (line.equals(new StringBuffer(line).reverse().toString()));
   }
}

I used the StringBuffer integrated class of Java and the meta character "/W" (all non-word characters, must be capital W). Please feel free to criticize or discuss!