title: is it possible for an interface to have an already instanced object as an attribute?
body: <p>I am creating an interface with many implementing classes and there is an attribute they must all have;
  I guess it's better to put that attribute in their interface than writing many constructor lines, but attributes can only be static final and require to be immediately initialized.</p>
  
  <pre><code>public interface Interface{
  
       static final AttrType attribute = new AttrType( *something* ); 
  
  </code></pre>
  
  <p>I have 2 problems: this attribute is a class and its constructor needs some other type parameters not just ints, and also it shouldn't be initialized here, I need all implementing classes of the interface to work on the same instance of AttrType which as i said I won't instantiate in the interface.</p>
  
  <p>So, as I am not expert enough, is there a way to do this in the interface or I should just write a line in every  subclass' constructor to put in the one AttrType instance they need?</p>