第一种：用HomeBrew下载Maven
1 . 先搜索一下有哪些Maven的版本
brew search maven
结果
==> Formulae
maven ✔ maven-completion maven-shell maven@3.2 maven@3.3 maven@3.5
==> Casks
mavensmate homebrew/cask-fonts/font-maven-pro homebrew/cask-fonts/font-maven-pro-vf-beta
2：选择一款合适的版本
brew install maven@3.5
3：成功
Updating Homebrew...
==> Downloading https://www.apache.org/dyn/closer.lua?path=maven/maven-3/3.5.4/binaries/apache-maven-3.5.4-bin.tar.gz
==> Downloading from https://mirrors.bfsu.edu.cn/apache/maven/maven-3/3.5.4/binaries/apache-maven-3.5.4-bin.tar.gz
######################################################################## 100.0%
==> Caveats
maven@3.5 is keg-only, which means it was not symlinked into /usr/local,
because this is an alternate version of another formula.
If you need to have maven@3.5 first in your PATH run:
echo 'export PATH="/usr/local/opt/maven@3.5/bin:$PATH"' >> ~/.profile
==> Summary
🍺 /usr/local/Cellar/maven@3.5/3.5.4_1: 104 files, 10.2MB, built in 6 seconds
4:如果碰到没有权限写入某文件就用下面的
chmod 777 某文件
