Re: Question on binary files

Mark Space <>
Wed, 27 Aug 2008 11:03:14 -0700
Tom A. wrote:

In Pascal, it was easy to write this thing out to a file :
write(datastructure) and all 10 words (100 or so fields), were
written out.

Besides serialization and the obvious (write to an OutputStream), don't
overlook the use of java.nio.ByteBuffer. This class has methods for
writing all types of primitives as well as control over endianness.
Very handy when you're trying to read those old mainframe data files.

Serialization is tricky. You're implicitly making parts of a class
public that you might not realize. It's best to use classes that are
explicitly designed for serialization (like your struct was explicitly
designed to match the required file fields). You can just pop
"Serialization" onto any class but it's not a great idea to do so.

Highly recommended: check out the sections on serialization in
_Effective Java_ by Joshua Bloch.

But I was wondering how Java programs do this sort of thing. I'm sure
I _could_ pack up the structure, and I'm sure there are many ways to
do it, but I was wondering if there is a preferred way, or an easier

However, bit fields are passe in Java. Use enumerations. If you have a
bit field like this:

   int OPTION1 = 1;
   int OPTION2 = 2;
   int OPTION3 = 4;
   int OPTION4 = 8;

where the options are designed to be | together, use an EnumSet instead.
  It's nearly as efficient as OR'ing the ints together yourself, and
it's much better encapsulated.

And rather than use enumerations as indexes into arrays, use EnumMap
instead. Again, nearly as efficient as using arrays directly and much,
much better encapsulated.

Also in general, enumerations are well designed for serialization, and I
think the same applies to EnumSet and EnumMap. Just write 'em out to disk.

Again, see _Effective Java_ for more detail.

Who realizes that very few people would even be interested in a text
based dungeon game.

You'll need to add some art, but actually rogue-like games are still
popular. Final Fantasy Tactics kind of revived the genre, and I've
played imitators like Luminous Arc recently. Etrian Odyssey is on my
list (another rogue-like) as well.

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