Java byte数组转16进制字符串

    private static String toHexString(byte[] buf) {        if (buf == null || buf.length == 0)            return null;        StringBuilder sb=new StringBuilder(buf.length*2);        for(int i=0;i<buf.length;i++){            sb.append(Integer.toHexString(buf[i]>>4&0xf));            sb.append(Integer.toHexString(buf[i]&0xf));        }        return sb.toString();    }