I'm forking this off from the mammoth RPG400-L thread called "RPG -
I'm not dead yet!". The moderator requested the discussion be moved
to MIDRANGE-NONTECH, so here it is.
A couple of points from that thread that I wanted to continue, because
my knowledge is insufficient in these areas:
1. How "close to the metal" is IBM's JVM on the i? Apparently it's
pretty darn close, but that is not the subjective impression I've
gotten, from my (admittedly limited) use of it on V5R2. There was
another thread (I think on MIDRANGE-L) not too long ago from someone
asking if Java performance on the i has improved for 7.1, or whether
he should prepare to continue to be disappointed.
The thing is, on V5R2, it *feels* like RPG is blazing fast (well, as
fast as the machine can go), and Java is dog-slow. Then on top of
that, Java seems to need Qshell and PASE, adding a layer of
inconvenience, if not performance penalty.
2. Regarding Java's integration with the i; and how that compares
with Java's integration with other platforms: In my opinion, Java is
not particularly well integrated with any platform, in the sense that
no hardware or operating system that I'm aware of was designed
specifically to run a JVM. From the other direction, Java doesn't
seem designed for any particular hardware or operating system (it's
just up to the respective JVM implementors on the various platforms).
That said, it still *feels* to me like Java is integrated better on
other platforms, partly because of the Qshell thing I mentioned before
(on other machines with a JVM, Java lives in the "native" command
environment). Also in part there is the EBCDIC issue, which seems to
thwart practically everything i (not just Java), since essentially
nothing else in the world uses it.
In the RPG400-L thread, it was mentioned that IBM gave RPG some nice
hooks for Java that are perhaps better than what is available for
other languages or other platforms. But the trend in the rest of the
world seems to be to just accept the JVM itself as the platform, and
write languages that target it. (Except Microsoft, which developed
the competing .NET, which is roughly analogous to JVM.) Now there are
tons of languages for JVM (as well as for .NET), and these naturally
interoperate stunningly well. But to my knowledge, these are not
available for IBM's i JVM, because of the unusual architecture of the
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