Whenever I try to run a test of RuntDeale (a basic program that creates a JFrame, with a black background, that is not resizable), in the standard form that I make my programs in:

MainClass:
  constructor() {/* set up key components to initialize a program instance */}
  program-entry() {/* make an instance of the main class (program), and run it with its "run" method */}
  run() {/* program logic */}

Here, it raises java.lang.ClassNotFoundException:

Error: Could not find or load main class RuntDeale.code.Main
Caused by: java.lang.ClassNotFoundException: RuntDeale.code.Main

With the recurring problem (in the "Problems" tab) with "The project was not built due to "Failed to init ct.sym for C:\Users\Administrator\AppData\Local\Temp\eoiDF83.tmp\plugins\org.eclipse.justj.openjdk.hotspot.jre.minimal.stripped.win32.x86_64_15.0.1.v20201027-0507\jre\lib\jrt-fs.jar". Fix the problem, then try refreshing this project and building it since it may be inconsistent" (I don't know if this is related to the problem, but I thought I'd include it just in case it was).

Could someone please explain why it won't run?

Thanks!
Cheers!