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);
}