Java 中把一个字符串反转

private static String reverse01(String str) {
if (str == null || str.length() == 0) {
return null;
}
StringBuilder sb = new StringBuilder(str.length());
for (int i = str.length() - 1; i >= 0; i--) {
sb.append(str.charAt(i));
}
return sb.toString();
}