1) scanning the string simultaneously from beginning to end and from end to beginning. comparing both chars. If not equals not palindrom. If the 2 pointers meet - palindrom. Here we go Java: package palindram; public class Palindarm { static boolean isPalindrom(String str) { if (str == null || str.length ()==0) return false; int left=0, right=str.length()-1; for (;left=right && str.charAt(left)== str.charAt(right); } /** * @param args */ public static void main (String[] args) { // TODO Auto-generated method stub System.out.printf("%b\n",isPalindrom("")); System.out.printf("%b\n",isPalindrom("aba")); System.out.printf("%b\n",isPalindrom("abab")); System.out.printf("%b\n",isPalindrom("abababa")); System.out.printf("%b\n",isPalindrom("a aa a")); } }