What’s the default Java (jave-jre) version on 19.10? Is it installed by default?
Is this what you are looking for?
$ apt search java | grep jre
WARNING: apt does not have a stable CLI interface. Use with caution in scripts.
default-jre/eoan 2:1.11-72 amd64
default-jre-headless/eoan 2:1.11-72 amd64
nvidia-openjdk-8-jre/eoan 9.+8u77~10.1.168-1build1 amd64
openjdk-11-jre/eoan-updates,eoan-security 11.0.6+10-1ubuntu1~19.10.1 amd64
openjdk-11-jre-dcevm/eoan 11.0.3+1-1 amd64
openjdk-11-jre-headless/eoan-updates,eoan-security 11.0.6+10-1ubuntu1~19.10.1 amd64
openjdk-13-jre/eoan 13+33-1 amd64
openjdk-13-jre-headless/eoan 13+33-1 amd64
openjdk-14-jre/eoan 14~18-1 amd64
openjdk-14-jre-headless/eoan 14~18-1 amd64
openjdk-8-jre/eoan-updates,eoan-security 8u242-b08-0ubuntu3~19.10 amd64
openjdk-8-jre-headless/eoan-updates,eoan-security 8u242-b08-0ubuntu3~19.10 amd64
Oh! And as for the default install - assuming this is the package you are referring to:
$ apt search default-jre
Sorting... Done
Full Text Search... Done
android-platform-tools-base/eoan,eoan 2.2.2-3 all
base tools for developing applications for the Android system
default-jre/eoan 2:1.11-72 amd64
Standard Java or Java compatible Runtime
default-jre-headless/eoan 2:1.11-72 amd64
Standard Java or Java compatible Runtime (headless)
java-package/eoan,eoan 0.62 all
Utility for creating Java Debian packages
This is my 19.10 install. But do note that this is a minimum.
I think the manifest will layout what is default.
@fossfreedom 
Am I right on that?
Java isn’t installed by default. I ran a batch file to install loads of software, but that doesn’t mention Java. I am guessing that some of the software I installed had an old version of Java as a dependency, so it got installed through that. In future I will check the Java version with
java -version
and if it’s too old, install the default version with
sudo apt install default-jre
Just in case, you can search ubuntu packages here :
https://packages.ubuntu.com/search?keywords=jre&searchon=names&suite=eoan§ion=all
Correct!
We dont ship any java based default apps so it’s not installed on our iso.
Kindly correct me if I’m wrong: the default java version can be either JRE or JDK.
You will need the Java Development Kit (JDK) in addition to the Java Runtime Environment (JRE) in order to compile and run some specific Java-based software. The JDK comes with a Java-c compiler, which is lacking in the JRE.
The JDK is therefore a heavier package.
The default JDK can be installed with the command
sudo apt install default-jdk
The default Java version at the moment is Java 11 (I have installed it this week). Here is a very well written and complete article about how to install the most recent, as well as older Java JRE and JDK versions.