CDK code seems to be compatible with Java 5 or even with Java 1.4. But the package was assembled with Java 6, which makes it impossible to be run with Java 5.
Expected:
The package is assembled with appropriate backward compatibility compiler option.
My Linux systems do not have a maintained Java5 installation, and as such due to security issues. You will have to compile yourself or find someone in the community to set up a Nightly build server running with Java5. I don't think really is a bug; I'll move it to the feature requests.
The code could be compiled with any JDK, but compatibility options should be set to the lowest the code accepts (e.g. "-source 1.5" if CDK uses for example generics or even "-source 1.4" if none of Java6 features are used).
I've doublechecked build.xml from CDK 1.2.8: all <javac ...=""> targets have source="1.5". The situation changed in 1.3.8, where source="1.6". So I wonder: if there is any Java6-specific code in CDK, that does not allow the binary package to be compiled in a way to be run on Java5? If not, fixing build.xml is trivial.
It was the SMSD patch that introduced this change, and I think that needed source level 1.6. The CDK requires Java1.6 in general now (as Java 1.5 is no longer supported).
But, let's try how far we get with -source=1.5...
I/we need to dig up a part of the build system not used in a while: conditional building of code depending on the Java version installed :) We have been there before...
Egon
Finally, I've made an effort to clean up the code to be compilable with JDK 1.5.
Please, check here:
https://github.com/dmak/cdk/commit/7c24db7ba1697c67b0b1c4c06dc2c17704faa684
P.S. I have found the following relative issue in the maillist: https://sourceforge.net/mailarchive/forum.php?thread_name=B73B531D1EDAF244B159C9254673B2E0F5BDEB%40MAILSRVR.Galenea.com&forum_name=cdk-user
Looks good to me. I applied it to cdk-1.4.x.
I think master will be Java7 based. I will send around email about that.