This question already has an answer here:
I want the java plugin to work in Firefox and so I want to be clear on something. It appears that the default JRE (OpenJDK) that one gets from doing
sudo apt install default-jre
will not work, and so it is useless. One needs either
oracle-java8-installer. Is this right?
Previous answers to questions about this just say install icedtea, but do not explain why? I am asking specifically if this is because openjdk cannot be made to work in Firefox. And I am wondering why in the world that would be? Strikes me as absolutely crazy.