1、创建java8.rb（打开以下链接复制即可）

      https://github.com/Homebrew/homebrew-cask-versions/pull/7261/commits/ec644edfefe89d83a35632ab033da30b70952bbf

2、官网下载mac os版本jdk

    执行 openssl dgst -sha256 ~/Downloads/jdk-8u212-macosx-x64.dmg 获取sha256 

3、修改java8.rb内容

version` to: `version '8u212,b10:59066701cf1a433da9770636fbc4c9aa'`⁩ 

现在地址右键检查红色框部分按对应顺序复制即可

`sha256` to: `sha256 '9bcb4265a55e2fe63b9c58ca6c5a54eb6dda303bb69510ca6eddc2f088e41b2a'` # 第2步执行的结果

`url` to: `url "file:///Users/xingwu/Documents/tmp/jdk-#{version.before_comma}-macosx-x64.dmg",` # file + 存放的位置

`pkg` to: `pkg 'JDK 8 Update 212.pkg' #点击dmg后的文件名称

4、执行  brew cask install java8   不出意外就可以看见  java8 was successfully installed!

issues

https://github.com/Homebrew/homebrew-cask-versions/issues/7253