Java - USC2字符串截取

public static String cutString(String s, int length) throws Exception{
      byte[] bytes = s.getBytes("Unicode");
        int n = 0;
        int i = 2;//标志两位 [0]=-2 [1]=-1
        for (; i < bytes.length && n < length; i++) {
            if (i % 2 == 1) {
                n++;
            } else {
                if (bytes[i] != 0) {
                    n++;
                }
            }
        }
        if (i % 2 == 1) {
            if (bytes[i - 1] != 0)
                i = i - 1;
            else
                i = i + 1;
        }
        return new String(bytes, 0, i, "Unicode");
    }