Re: Compile Java using different JDK versions on AS400

["Bruce Jin" <brucej@xxxxxxxxxxxxxxxxxxxx>]

I can use
 java -djava.version=1.2 MyClass
But javac does not take flag -djava.version. I got the following error:

javac -Djava.version=1.2 MyClass.java
javac: invalid flag: -Djava.version=1.2

Bruce

-----Original Message-----
From: Larry Loen <lwloen@us.ibm.com>
To: JAVA400-L@midrange.com <JAVA400-L@midrange.com>
Date: Friday, April 13, 2001 12:23 PM
Subject: Re: Compile Java using different JDK versions on AS400


>
>First, let me belabor the obvious about run-time implications of the
>compiles.
>
>If your source compiles under both 1.1 and 1.2, then I have always been
>able to compile it under 1.1 and use the resulting class files under both
>1.1 and 1.2.
>
>However, things compiled under 1.2 with javac can be marked in such a way
>that 1.1 does not run them, thinking them uplevel in some way, even if you
>don't use 1.2 classes.
>
>I would still do CRTJVAPGM on the resulting class files if you want the
>best performance -- if there are interoperability problems between 1.1 and
>1.2, I haven't run into them with or without CRTJVAPGM, though of course
>there can always be bugs.  This matters as you may be able to have a 1.1
>version serve both 1.1 and 1.2 apps instead of two jar files or some such
>thing.
>
>Keep in mind that the OS/400 JVM is more closely tied, in the end, to the
>OS/400 than the Java level.  Our JVM tends to support multiple, specified
>Java versions in the context of one OS/400 release.  Other JVMs tend to be
>self-contained.  Support for a given Java version is based on possessing
>that particular version's JVM on other boxes.
>
>This difference is ordinarily invisible, but it may help a little here when
>you get down to actually running classes.
>
>Now, on to javac.  If you do the actual javac on the '400, then be sure
>that you are running javac using the Java version you want.  The
>documentation describes, for running javac under QShell, how to specify a
>version.
>
>It says:
>
>If you have JDK 1.1.x installed on AS/400 as your default, but you need to
>run the 1.2 version of the java command, enter this command:
>
>javac -djava.version=1.2   MyProgram.java
>
>
>
>Obviously, this should work the other way around.
>
>
>
>Larry W. Loen  -   Senior Java and iSeries Performance Analyst
>                          Dept HP4, Rochester MN
>
>
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