java - Interface method referencing a concrete class as parameter causes coupling? -

i thinking programming interfaces , not concrete classes, had doubt: should interface method able hold references concrete classes?

suppose following scenarios:

1)

public interface abstype1 {     public boolean method1(int a); // it's ok, primitive types here } 

2)

public interface abstype2 {     public boolean method2(myclass a); // think have coupling here } 

should choose different design here in order avoid latter? e.g.

public interface myinterface {} // yes, empty  public classe myclass implements myinterface {     // identical previous "myclass" }   public interface abstype2 {     public boolean method2(myinterface a); // better (as long                                            // interface stable) } 

but there's still doesn't convince me... feel uncomfortable declaring empty interface, though saw else doing so. maybe , abstract class work better here?

i little bit confused.

edit:

ok, i'll try more specific making example. let's i'm desining shopcart , want of course add items cart:

public interface shopcart {     public void addarticle(article a); } 

now, if article concrete class, if implementation changes on time? why think of making interface, again, it's not suitable @ least @ semantic level because interfaces should specify behaviours , article has none (or none... guess it's sort of entity class).

so, i'm ending right conclusion making article abstract class in case best thing... think it?

i use interfaces because composition better inheritance. "should interface method able hold references concrete classes ?", why shouldn't? classes within package coupled, it's fact , common use technique. when marked relation in interface see on classes dependent implementation. dependency or composition relations not inheritance avoid abstract class.