Do a conversion to Java 5. This doesn't have to be an all-at-once conversion. QFJ already compiles with Java 5. However, it would be nice to eliminate the dependency on the external backport-concurrent library by a move to Java 5. It would also make it easier to support SSL with MINA since the SSL support classes are in Java 5.

The key issue here is that we'd like to maintain Java 1.4 compatibility. This means using a tool like Retroweaver or Retrotranslator to create Java 1.4 compatible JAR files during the build.