From Java Platform, Standard Edition 8 Names and Versions:
In JDK 8 and JRE 8, the version strings are 1.8 and 1.8.0
Why? Because the developers of Java chose to name the versions like this. I can only assume the real reasons, but I think it is, because naming it Java 8 implies that it is new and much better than Java 7 but keeping the version bump from 1.7 to 1.8 indicates that it is still version 1.x and therefore still backwards compatible. In the end it is marketing.
See also Why is Java version 1.X referred to as Java X?.
Answer from leonardkraemer on Stack OverflowVideos
Because of licensing and dependency issues, if I understand correctly, our team is only allowed to use Java 8 EE 7 JDK 1.8. Searching for JDK 1.8 returns the link titled `Java SE Development Kit 8 - Downloads - Oracle`. Honestly, I am completely lost trying to install Java on my machine. Why doesn't Java have something like `sudo apt-get install java8` :P
Yes, I understand it's because of Oracle and weird licensing stuff.
From Java Platform, Standard Edition 8 Names and Versions:
In JDK 8 and JRE 8, the version strings are 1.8 and 1.8.0
Why? Because the developers of Java chose to name the versions like this. I can only assume the real reasons, but I think it is, because naming it Java 8 implies that it is new and much better than Java 7 but keeping the version bump from 1.7 to 1.8 indicates that it is still version 1.x and therefore still backwards compatible. In the end it is marketing.
See also Why is Java version 1.X referred to as Java X?.
Before Java 9, Java version X was internally specified as 1.X according to these specs.
Then came JEP 223 which proposed to change the version to just X starting with Java 9.
It should be noted that different tools may even use other conventions. For instance in Gradle there is JavaVersion.VERSION_1_9, JavaVersion.VERSION_1_10 and they only switch to the new convention in JavaVersion.VERSION_11 (see their code comment).
Usually you install the openjdk like this:
sudo apt-get install openjdk-8-jdk
Maybe this is the problem. You can look this up at http://openjdk.java.net/install/index.html. If you do this you might have fixed this problem. But cant imagine why your command give this result.
I installed oracle-jdk8. If you need,
sudo add-apt-repository ppa:webupd8team/java && sudo apt update
sudo apt install oracle-java8-installer
With Java 24 on the corner, most of the larger organizations still use Java 8. Does it not make sense to upgrade java versions and give new features some rest. This would also solve many security issues.