String字符串反轉方法

public static char[] reverse(char[] buffer, int start, int len) {
if (len <= 1)
return null;
int num = len >> 1;
for (int i = start; i < (start + num); i++) {
char c = buffer[i];
buffer[i] = buffer[start * 2 + len - i - 1];
buffer[start * 2 + len - i - 1] = c;
}
return buffer;
}