Question

I want to write a BigInteger to a file.
What is the best way to do this.
Of course I want to read (with the program, not by human) it from an inputstream.
Do I have to use an ObjectOutputStream or are there better ways?

The purpose is to use as less bytes as possible.

Thanks
Martijn

Answer 1

Java serialisation (ObjectOutputStream/ObjectInputStream) is a general purpose way of, er, serialising objects into octet sequences. However, there are issue with serialisation.

To be uber efficient, BigInteger has toByteArray and a constructor that takes byte[]. Then you need some way to represent byte[] (including length) in a stream. For instance, you could use DataOutputStream to writeInt the length, and follow that with the raw data.

Streams can, of course, be compressed with a suitable decorator of your choice.