一、原因
IntelliJ IDEA期待一個the standard Groovy SDK
二、解決方案：
下載安裝Groovy就可以了
官網下載地址：
通過包管理工具下載Groovy：
SDKMAN! (The Software Development Kit Manager)
This tool makes installing Groovy on any Bash platform (Mac OSX, Linux, Cygwin, Solaris or FreeBSD) very easy.
Simply open a new terminal and enter:
$ curl -s get.sdkman.io | bash
Follow the instructions on-screen to complete installation.
Open a new terminal or type the command:
$ source "$HOME/.sdkman/bin/sdkman-init.sh"
Then install the latest stable Groovy:
$ sdk install groovy
After installation is complete and you've made it your default version, test it with:
$ groovy -version
That's all there is to it!