Gradle and Maven (or Both)
The world of build tools evolve from simple compilation (gcc) to make files, then evolution of ant(+ivy) and Maven, now the latest build tool is Gradle.
Its always a puzzle which build tool to choose maven, gradle or both (maven and gradle). Sometime its first time project setup or could be migration from existing tool but it always a debate to choose one of the existing one.
There have been lot of talks and discussion on Gradle, maven (and/or Gradle vs maven). There are Buzz around that Android/google adopted Gradle as its standard build tools.