Hi,

I am not familar with the InflaterInputStream, and you did not say much
about the kind of compression. In fact, *every* byte array can be viewed
as 'compressed' if you specify an adequate compression algorithm. So,
without knowing the algorithm, your problem cannot be solved.

Having said this, look at some of your byte arrays in detail. Normally,
because of what I said above, most compression algorithms add some kind
of header to mark the byte array as 'compressed by this algorithm'.

Hth,
Ingo

PS: Note that even if a byte array starts with "Compressed with GZIP
Version 3.45", this might be a coincidental sequence of bytes! :-)
So, If you *really* want to be sure, it would be a good idea to add a
header in any case (even, if the byte array is not compressed).

Hello again..  Please refrain from multi-posting.
<http://www.physci.org/codes/javafaq.jsp#xpost>

Also, please be clear that you are posting to Usenet, not Google.
<http://www.physci.org/codes/javafaq.jsp#usenet>

A simplistic approach is to just try to decompress it.  If that fails
then it's not compressed (or is corrupted).  This simplistic approach
assumes that the majority of the stored data is compressed.  The
approach can be slightly optimized by checking the header yourself
before attempting a decompression.  I've used this technique in
interceptors for decompressing CORBA traffic.

The only real risk is of successfully decompressing something that
wasn't compressed.

Antti's approach, however, is cleaner.

John
http://schemaspy.sourceforge.net

The entropy of compressed data tends to be higher than that of
uncompressed data. But this is just a statistical observation.-)

Strange setup you have there where you don't know what kind of data
format you are dealing with.

 Harald.

but a boolean on the front of the stream to tell you is the easiest
way.

I am beginning to realize the wisdom of putting a field on the front
of any stream giving the version.  Otherwise it becomes impossible to
deal with old format files later on.

Other that that, look at the two files with hex viewer to see if
the9re is a recognisable signature.

see http://mindprod.com/jgloss/hex.html