Re: [Cdk-devel] Libraries and Java versions

[Egon W. <e.w...@sc...>]

On Tuesday 15 February 2005 10:40 am, Peter Murray-Rust wrote:
> We develop on both Java 1.4 and 1.5 and discovered yesterday that byte code
> *compiled on 1.5* will not run on 1.4 systems (even simple programs like
> HelloWorld). It fails with an incompatible version number (actually
> requires version 49.0 (sic) of Java). Therefore if we compiled and released
> JUMBO on 1.5 machines it would fail anywhere with 1.4. [We assume that J1.4
> bytecode runs on 1.5 systems]
>
> Q. what strategy do the various groups have for this? Do you have any idea
> of the rate of take up of J1.5?

Jmol uses this in the build.xml:

  <property name="build.compiler" value="javac1.4" />
  <property name="java.version" value="1.4" />

and

  <target name="applet-classes" id="applet-classes" depends="init">
    <mkdir dir="${applet.classes.dir}"/>
    <property name="build.compiler" value="javac1.1" />
    <!-- mth 20040713 ... with the Sun Java 1.5 compiler the default
         source code version is 1.5. And one cannot generate code for
         a 1.1 virtual machine from 1.5 source. Therefore, in order to
         compile for the 1.1 jvm, we need to specify that the source
         version is 1.3. (Note that we cannot use source=1.4 because
         of assertions)

miguel 20041121
I do not know recall exactly what I meant by the statement
in (parentheses) above. I *think* that what I was saying
is that if you say 'source=1.4' then one also cannot
generate code for a 1.1 jvm, because of the special
support for assertions (which were introduced in 1.4).
    -->
    <javac srcdir="src" destdir="${applet.classes.dir}"
           debug="${debug}" deprecation="${deprecation}"
           optimize="${optimization}"
           source="1.3" target="1.1"
           includesfile="applet.classes"
           classpathref="applet-project.class.path" />
    <!-- mth tried to use exclude and excludefiles, but it did not work -->
    <delete includeEmptyDirs="true">
      <fileset dir="${applet.classes.dir}/org/openscience/jmol">
        <include name="*.class" />
      </fileset>
    </delete>

Note the target="1.1" attribute, and the comment on why source="1.3" was 
added...

I think target="1.4" should work.

> javac 1.5 has a switch -target 1.4 which we assume generates byte code
> compatible with J1.4 systems.
>
> Q does this work?

Miguel normally makes sure it works.

> Q. have you used and deployed code of this sort?

See above.

> Q is it a good strategy?

Better would be to try to compile *and* test with both JVMs...

> Q should our community (Jmol, JCP, CDK, QSAR, Octet, JOElib, JUMBO) have a
> communal view? If we all do the same thing we are limited by the slowest. I
> assume that Jmol, for example, need to retain considerable backward
> compatibility

Indeed.

Egon