Where is the right place for annotation processing?

I write simple application. I don't want to use any frameworks. Please suggest me right place to hold annotation processing.

I have a few lines in main method:

String myString = (@NonNull String)list;

And I created @interface:

@Target({ElementType.TYPE_USE, ElementType.TYPE_PARAMETER})
public @interface NonNull {
}

Which step should I take next? Can I work with annotations without using reflection? Could you expose for me samples of such annotation processing code?