Could not find or load main class in Eclipse

问题

I created a new java project in eclipse. This is the first time I am using it.
After creating java files. I tried running a java file by right clicking->Run As-> Java Application
It showed the error :

Error: Could not find or load main class ISBN
Caused by: java.lang.ClassNotFoundException: ISBN

What could be the reason for this error? How do I fix it?

来源：https://stackoverflow.com/questions/65881449/could-not-find-or-load-main-class-in-eclipse