Unable to install java8 with homebrew

New command is now :

brew install --cask homebrew/cask-versions/adoptopenjdk8

This has already been answered as a github issue: https://github.com/Homebrew/homebrew-cask-versions/issues/7253

TLDR: the java8 artefact refers to the Oracle distribution, which has ceased being supported/available. If you really need java 1.8 instead of the latest versions you can take a look at AdoptOpenJDK/homebrew-openjdk.

The command is now brew cask install homebrew/cask-versions/adoptopenjdk8

brew install homebrew/cask-versions/adoptopenjdk8 --cask

In the latest changes of homebrew cask will have to be at the last.