This would seem to be a potential candidate for a multi-release
jar[1], if you can figure out a reasonable way to get a build system
to generate one.

The 4 uses I found of comparing byte[] could be refactored to call a
new utility class to do the comparison. The "regular" implementation
could be java 7 compatible, and the jdk 9 version would be in the
META_INF folder.
Even for the java 7 compatible version, it might be worth exploring
how much improvement would come from using Unsafe to read int or long
values from the byte[] and compare those.

For Hash234, I would think the whole class could be handled for the MR jar.

[1] -



On Fri, Jan 8, 2021 at 1:36 PM Lasse Collin <> wrote:
> On 2021-01-08 Brett Okken wrote:
> > Are there any plans to update xz-java to take advantage of newer
> > features in jdk 9+?
> There aren't much plans at all. Adding is likely to
> happen in the next release, whenever that will be.
> Apache Commons Compress 1.20 requires Java 7. It depends on XZ for
> Java. I think it wouldn't be good to make XZ for Java require a newer
> Java version than Commons Compress but it could be discussed with
> Commons Compress developers. There's a bug with .7z files that requires
> changing both XZ for Java and Commons Compress so I could ask about the
> Java version too.
> > For example, Arrays.mismatch[1] leverages vectorized comparisons of 2
> > byte[]. This could be leveraged in the getMatches methods of BT4 and
> > HC4 as well as the 2 getMatchLen methods in LZEncoder.
> >
> > Another example would be to use a VarHandle to read int values out of
> > a byte[][2], which would be useful for the calcHashes method in
> > Hash234.
> Thanks! These sound interesting. If they make big enough difference, it
> could be a good reason to require Java 9.
> I will need to check out the LZDecoder improvement from the other
> message too, and perhaps a few variations of it. Thanks!
> There are multiple things in XZ Utils that I try to look at in the near
> future so it will be a while until I will play with the Java code.
> --
> Lasse Collin  |  IRC: Larhzu @ IRCnet & Freenode

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