java message digest algorithm

Hi Experts,
I would like to implement my own message digest algorithm in java based on the existing sha256 algorithm to make it resumable (trust me, there's no other way).  Has anyone done this?  I have the java JDK source and so far can't even find the implementation of sha256, just the code that loads it...  

Thanks,
Mike
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threadyAsked:
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CEHJCommented:
to make it resumable
What do you mean by that?
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threadyAuthor Commented:
I mean so you can store the state of the internal variables, serialize the digest instance in the middle of a large checksum calculation and read it back at a later time...   It's not possible with the code from the JDK since the source is not even included for the algorithms however (found that out today).  I'll likely accept this answer as the solution unless you or someone else has any other idea...

Thanks,
Mike
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threadyAuthor Commented:
I did see that one, thank you.  We can't use it though, because we can't give our source to the customer (GNU license)...
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CEHJCommented:
I'm betting there's also one in Apache Commons Codec with a license that might do it for you (though not too sure about license)
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threadyAuthor Commented:
Thanks
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