java reverse a string
// Library approach public static String solution(String str) { // StringBuilder is not thread-safe, use StringBuffer return new StringBuffer(str).reverse().toString(); } // DIY approach public static String solution(String str) { char[] chars = str.toCharArray(); for(int i = 0, j = str.length() - 1; i < j; i++, j--) { char ch = chars[i]; chars[i] = chars[j]; chars[j] = ch; } return new String(chars); }