Ubuntu – Problems installing Java 8 onto Ubuntu 18.04 – Errors on oracle-java8-installer and java-common

Run the following commands from a Terminal:

sudo rm /var/lib/dpkg/info/oracle-java7-installer*
sudo apt-get purge oracle-java7-installer*
sudo rm /etc/apt/sources.list.d/*java*
sudo apt-get update
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java7-installer

Information about what PPAs are, as well as tips on recognizing which of them are unsafe, can be found here.

Glossary

Command, command line: the traditional Unix environment , where you type commands to tell the computer what to do.

Terminal: an application that allows you to access the command line. Open it by hitting its keyboard shortcut, Ctrl Alt T

Yes, it's gone forever unless you have a support contract with Oracle.

Java 6 is no longer provided to the general public by Oracle because it reached end-of-life way back in February 2013, so you can't download it from Oracle unless you have a support contract with Oracle, which allows you to manually download it (after logging in) until December 2018.

I'd recommend using Java 8 or later. It still gets security updates, and it will compile and run Java 6 programs just fine. If you need to compile something so that it will run on a Java 6 JVM, you just need to add -target 1.6 to your javac line.