How to parse byte[] (including BCD coded values) to Object in Java

I'd like to know if there is a simple way to "cast开发者_运维问答" a byte array containing a data-structure of a known layout to an Object. The byte[] consists of BCD packed values, 1 or 2-byte integer values and character values. I'm obtaining the byte[] via reading a file with a FileInputStream.

People who've worked on IBM-Mainframe systems will know what I mean right away - the problem is I have to do the same in Java.

Any suggestions welcome.

No, because the object layout can vary depending on what VM you're using, what architecture the code is running on etc.

Relying on an in-memory representation has always felt brittle to me...

I suggest you look at DataInputStream - that will be the simplest way to parse your data, I suspect.

Not immediately, but you can write one pretty easily if you know exactly what the bytes represent.

To convert a BCD packed number you need to extract the two digits encoded. The four lower bits encode the lowest digit and you get that by &'ing with 15 (1111 binary). The four upper bits encode the highest digit which you get by shifting right 4 bits and &'ing with 15.

Also note that IBM most likely have tooling available if you this is what you are actually doing. For the IBM i look for the jt400 IBM Toolbox for Java.