Ant, from Jakarta project at the Apache Foundation, has become a de facto standard for building Java projects. You may already be using it to create automatic builds. It's easy enough to tailor those builds to your needs by customizing the build files; but what if you want to wait until run time to set certain properties? This article shows you how to extend Ant to produce builds that are interactive at run time; users can follow prompts to change parameters each time they conduct a build without having to deal with unfamiliar build files. You can incorporate this functionality into your builds to provide a smoother and more flexible experience for your end users.