"Could not find or load main" message, how do I fix it?

It means, it could not find a file named main (usually the main source file) under the source path listed in Build / Run Configuration.
When building or running, the goormIDE needs to know where the source files are located and the names of those files.
Even though it appears in [Project] > [Build/Run Configuration] in the top menu, if the content does not match the location of the actual source file, goormIDE cannot find the source file and cannot build/run it.
This usually happens when creating an empty project, which is caused by two things:
  1. 1.
    The folder where the actual main file is located is not set as the source path in the [Build/Run Configuration].
  2. 2.
    The main file does not exist under the source path.
First of all, make sure that the main file name and source file name shown in [Build/Run Configuration] are the same. Then, there are two ways to solve the problem.
  1. 1.
    (Recommended) Change the name of the main file to the name of the source file you want to build/run in [Build / Run Configuration].
  2. 2.
    Rename the source file's name to main you want to build/run.
If you make the name of the source file "main" in the current empty project, you can build/run it without any problem.
Please refer to Build/Run Configuration guide for more details.