It seems Debian does not support openjdk-8-jdk anymore due to a security issue. What is the easiest way to install openjdk-8-jdk for Debian 10 (Buster)?
Alternatively, you can use adoptopenjdk repository:
wget -qO - https://adoptopenjdk.jfrog.io/adoptopenjdk/api/gpg/key/public | sudo apt-key add -
sudo add-apt-repository --yes https://adoptopenjdk.jfrog.io/adoptopenjdk/deb/
sudo apt-get update && sudo apt-get install adoptopenjdk-8-hotspot