Editor does not contain a main type in Eclipse

Question

I have 64-bit ubuntu where I downloaded eclipse-jee-kepler-SR1-linux-gtk-x86_64.tar.gz. Here whenever I  compile and run a simple code in java like the one below:

public class Sample{

   public static void main(String[] args){
       System.out.println("YOLO");
   }
}

I always get an error: Editor does not contain a main type.
How can I resolve this error?

My project structure: