public static byte[] add(final String prefix, final long postfix) {
        if (prefix == null) {
            throw new NullPointerException("prefix");
        }
        byte[] agentByte = toBytes(prefix);
        return add(agentByte, postfix);
    }
copy google protocol buffer
https://github.com/google/protobuf/blob/master/java/src/main/java/com/google/protobuf/CodedOutputStream.java
commons/src/main/java/com/navercorp/pinpoint/common/util/BytesUtils.java