#220 do *not* use Arrays.copyOf(), performance seems to be inferior

[winfriedgerlach]

No description provided.

[cowtowncoder]

@winfriedgerlach Ok no real change wrt Arrays.copyOf(), but curious as to if you have something that points to such performance difference? Or did you do micro-benchmark?
(would have like used it mostly for bit more compact code)

[winfriedgerlach]

@cowtowncoder Very good question that I don't have the perfect answer for.

Very old comments (Joshua Bloch) say .clone() is the fastest way to clone an array. This is already challenged in some of the answers to that question. Most published benchmarks of "medium age" (e.g. some years ago) find that System.arrayCopy() is fastest.

Things seem to have changed quite a lot in the JDK recently (~beginning of 2023), so different Java versions may perform considerably differently:

• Java 21 has improved Arrays.copyOf() performance, see e.g. https://bugs.openjdk.org/browse/JDK-8301958
• Java 22 changed code again, https://bugs.openjdk.org/browse/JDK-8309665
• Newer benchmark still sees System.arrayCopy() slightly ahead of .clone(), cf. https://bugs.openjdk.org/browse/JDK-8302315 and https://gist.github.com/schlosna/975e26965ec822ad42034b3ea2b08676

Other quite new (2024) benchmarks find no significant difference between Arrays.copy() and System.arrayCopy() (note the absence of the JVM version under test...):
https://www.baeldung.com/java-system-arraycopy-arrays-copyof-performance

My own micro (and a little less micro benchmarks) showed System.arrayCopy() ahead most of the times, sometimes on same level as clone()/Arrays.copyOf().

As Jackson currently supports every Java version from Java 8 to 23, I recon it is safer to stick with System.arrayCopy() for now when optimizing for performance, even if there is probably almost no performance difference when using the most current (=2024) Java versions.

I definitely have to agree that the code is nicer with Arrays.copyOf()though, see cfe59fb