IntelliJ IDEA
IntelliJ IDEA – the Leading Java and Kotlin IDE, by JetBrains
Features
Upgrading Event Listeners to GWT 1.6
Google Web Toolkit 1.6 replaces EventListener class with EventHandler, so the existing code base needs an upgrade. In most cases IntelliJ IDEA can do this automatically — all you need to do is to press Alt+Enter on a highlighted listener and select Replace quick-fix.
IntelliJ IDEA will then upgrade your code:
This feature is available in Maia builds that you can download from EAP.