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1.) Don't know about close to the metal, but the 32-bit JVM is quite fast. V5R4 and above required.

2.) Java works just fine on the i. IBM has done some nice integration to RPG and you can also run Java classes from CL/QSHELL or from web apps. On other platforms including IBM I, Java is extensively used from web apps and services.

3.) In my experience EBCDIC to ASCII is handled automatically by QSHELL when calling Java classes.

Summary: Java works great on the I, depending on what you want to do.

Richard Schoen
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message: 1
date: Mon, 11 Jul 2011 18:04:20 -0400
from: John Yeung <gallium.arsenide@xxxxxxxxx>
subject: Java performance and integration

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 i.

Am I wrong? Or perhaps does no one care? ;)

John Y.

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