how java find main function.

Question

As I get, the main class inn a java code should be inside a class.
And as i know preveiwsly in other languages for example c++, we shoud define and call classmethods to works. But here in hello eorld sample i see that the main method is inside of a class. so ho the compiler can find it without defining?
If we have 2 classes what will hapend then?
i guss it should be forbidden to have 2 classes with main methot. but my main questios is still how can it find "main?