There is a message
Project has been compiled by a more recent version of the Java Runtime (class file version 57.0), this version of the Java Runtime only recognizes class file versions up to 52.0
I googled "JRE required for JDK 14" and there is no download to be found. In my Java control panel on Windows 10, it says I have the latest version of the Java platform. I cannot downgrade the JDK on my project since I am using a library which was completely compiled on Java 14. How (and where) does one upgrade the JRE to match with Java 14 and support version 57?
Answer
I assume you are using a Java version / build that is coming from Oracle on your machine. Since Java 11 the Oracle Java does not automatically update and install any new JRE on your system. Next to this Oracle does not provide JRE builds for Java 11+ anymore. You can only download JDKs from Oracle (Oracle JDK).
While Oracle provides an alternative with the Oracle JDK builds (see https://jdk.java.net/14/) you can not get a JRE here.
A very good alternative is AdoptOpenJDK that provides JREs for Java 14 here: https://adoptopenjdk.net/releases.html?variant=openjdk14&jvmVariant=hotspot