What to use? Parameterized class, abstract class or undefined type in Scala?

I have to implement a small graph library for my small Scala + JMonkey Engine game. Library will deal with shortest path caching for further queries. I will have to attach additional user data (like reference to another object) to my Vertexes and Edges. How to implement this behavior?

With:

1. parameterized class class Gr开发者_如何学Goaph[A, B] {...}, or

2. provide abstract class Graph {...} and implement user data variables later, or

3. provide abstract class Graph {...} and define type A inside the class?

Or maybe I'm missing something else?

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Here's a good article on this topic

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There are also traits which are mix between interface and concrete implementation.