More about Separated Interface Pattern and layered design

[Rajesh Khan]

So far I believe the following is an example of a separated interface pattern.

package domain;
public class domainClass
{ 	
  private InterfacA interfacea; 
  public void methodA()  {this.interfacea.methodA();}
  public domainClass(InterfacA interfacea){this.interfacea = interfacea}
}//End Class

package domain
public interface InterfacA
{ public void methodA();}

package service
public class InterfaceAImpl implements InterfaceA
{
 public void methodA(){Systemout.println("Some Method");}
}

package service
public class FactoryClass 
{
  public static InterfacA getInstance(String type)
  {
	  if(type.equals("domainClass"))
	  {  return new InterfaceAImpl(); }
  }
}

Some questions regarding Separated interface pattern and n layered design.
I have read that the job of the service layer is to provide services to the business layer. Theoretically Are domain objects
suppose to be available to the other layers or are they just suppose to be available to the service layer ?

[Rajesh Khan]

Since i was told that Domain objects are not allowed to have methods or functionalities in a different thread as this would oppose the single responsibility principle a lot has been clarified. The only question that remains is why would the interface have any relation at all with the domain objects then ?