CordovaError: Requirements check failed for JDK 1.8 or greater

If you have a Cordova Error after updating to Ubuntu 18.04, the easiest way to resolve this issue is removing openjdk-11 and reinstalling openjdk-8.

sudo apt purge openjdk-11-jdk-headless openjdk-11-jre-headless
sudo apt install openjdk-8-jdk

There is not support for the new java versions yet in Cordova/Android (at the post date)