https://dzone.com/articles/gradle-vs-maven
https://docs.gradle.org/current/userguide/what_is_gradle.html
Directed Acyclic Graphs 有向无环图
https://docs.gradle.org/current/userguide/getting_started.html#try_gradle
https://blog.csdn.net/yechaoa/article/details/80484468
Getting Started
Contents
https://www.cnblogs.com/mooreliu/p/4849898.html
http://zgljl2012.com/gradleda-bao-shi-zhi-ding-jdklu-jing/
https://discuss.gradle.org/t/error-gradle-2-2-1-requires-java-6-or-later-to-run-your-build-is-currently-configured-to-use-java-5/6382