Rescripter is an Eclipse plug-in that let's you define how to refactor Java code by writing JavaScript.
If you've ever found yourself making large-scale changes that you can describe easily but are laborious to do by hand - then Rescripter is for you.
In Eclipse go to Help | Install New Software... Create a new update site with the URL:
https://raw.github.com/activelylazy/Rescripter/master/update-site/target/site
For more details and examples see the tutorial
If you have any questions / comments / feedback email me dave@activelylazy.co.uk