Congratulations on the speedup. I'd be interested to hear how you generate the code. We're doing some code generation as well. We're using XSLT to generate Java from a small XML 'language'. Works much better than out initial approach of using Java to walk through a DOM and generate the code. Then we use com.sun.tools.javac.Main.compile() to compile the generated java files. It works, but it's a bit clumsy, since javac can only handle java files in the file system, not Strings or something else in memory. Maybe the tools API in JDK 6 will bring some improvements.