Oracle no longer provides compressed versions of JDK 😡 and require root to install (probably they also install an auto updater nagging you all the time)
Download .dmg from Oracle and put in a directory
cd directory-with-dmg
7z x jdk-8u181-macosx-x64.dmg
(alternatively, if you don't have 7zip mount dmg and copy out .pkg)
pkgutil --expand "JDK 8 Update 181/JDK 8 Update 181.pkg" jdk-pkg-unpacked
tar xvf jdk-pkg-unpacked/jdk180181.pkg/Payload
Contents/Home is now the JDK root
mv Contents/Home ~/jdk180181
Now you can put JAVA_HOME="$HOME/jdk180181"
and PATH="$PATH:$JAVA_HOME/bin"
and start using it