IntelliJ IDEA
IntelliJ IDEA – the Leading Java and Kotlin IDE, by JetBrains
Features
Google App Engine Support
If you are developing a Java application for Google App Engine, try Google App Engine Integration plugin for IntelliJ IDEA. It will be bundled with the first Maia EAP, but you can download it right now and use with IntelliJ IDEA 8.x
After plugin is installed, start the New Project wizard, select Google App Engine and specify path to the App Engine SDK (you can download it from here, for example). IntelliJ IDEA will add all required descriptors, libraries and create a run configuration for your application, so you can quickly get started with its development.