安装Jave8
1. 导入Webupd8 PPA
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
2. 安装
sudo apt-get install oracle-java8-installer
选择确认条款，用Tab键切换。
3. 设置为默认jdk
sudo apt install oracle-java8-set-default
4. 验证
$ java -version
java version "9"
Java(TM) SE Runtime Environment (build 9+181)
Java HotSpot(TM) 64-Bit Server VM (build 9+181, mixed mode)
安装Maven
apt install maven