Java has some surprising amount of dinamism in it

Not long ago I saw some java code from Simone Tripodi. It generates synchronization wrappers around arbitrary objects at runtime in a typesafe manner with a couple of easy to understand lines of code. The heavy lifting is done by the dynamic proxy mechanism available from Java 1.5 if I recall correctly.

The downside is that there seems to be a 30% to 40% performance impact based on some quick benchmark I've done. However one can not understate the value of not having to write or maintain code!

There are surprisingly many things one can do in Java in a typesafe manner (including things usually associated with dynamic languages) which helps catching more errors early (at compile time) and take full advantage of the different helper features available in IDEs (such as auto-complete).