I'm just getting back to java, and went and downloaded the latest Eclipse Oxygen. Once it's all installed, I try to launch and get the following error dialogue.
So I went and downloaded Java 8 and installed that. Once again I tried to open Eclipse. It still displays the exact same answer. Any idea on how to fix this?
On macOS you must install the full JDK - the JRE install isn't enough.
Get the full JDK from the Oracle site here.
If you install Java 9 you will need to use at least Eclipse Oxygen.1a (4.7.1a) but preferably the current Eclipse, for eariler versions of Eclipse install Java 8.