How to fix an error when creating a package in Java?

Question

Java

I reached the chapter about packages and interfaces in the book.
Console work is described there. And I work in IDE. In general, by analogy, I created the MyPack package. In it, I created the class Example.
I launch and errors take off. What did I do wrong? How to fix?
Screen - storage9.static.itmages.ru/i/16/1017/h_1476712670_...
UPD.
I don't know what and how. Clicked to run with coverage. Everything started without errors. Now everything works fine. What happened?