Class has been compiled by a more recent version of the Java Environment
IDE: Eclipse Oxygen.3
To temporarily correct the problem do the following:
Project menu > Properties > Java Compiler > Compiler compliance level > 1.8
A permanent fix likely involves installing JDK 9.
FYI 1.8 is what Java 8 is called.
Side bar
I recently returned to Java after a foray into C# (a breath of fresh air) and installed Eclipse Oxygen onto a clean system that had never had Java installed on it before. This default everything with a brand new install of Eclipse Oxygen yet somehow or other Eclipse can't get its own parameters to match the jdk that's installed. This is the second project I created and the second time I ran into this headache. Time to go back to C#?
Related Question
has been compiled by a more recent version of the Java Runtime (class file version 53.0)