java, generics - how to parametrize a class with a type T which BOTH: extends and implements sth

Question

I want to type class members, as well as args for methods, in a type T, which has to be a Node and implement my own interface Linkable.

Essentially, I would like to limit the vars to the small section of the inheritance 'tree' between Node and Linkable. Reason being I don't want to have to do all the casting inside the class, depending if I need to call methods of Node or methods of Linkable.

At the moment in my project I know I'm using only Nodes which implement Linkable, but this condition is not enforced in any way.

Pseudo-code below (only for illustration):

public class MyClass <T extends ??> {

T node1;
Bounds bounds1;

bounds1 = node1.boundsInParentProperty(); //Node specific method

node1.linkableSpecificMethod(); //method defined in Linkable interface
//....
}

Find your answer here: http://stackoverflow.com/questions/745756/java-generics-wildcarding-with-multiple-classes — Christian Frommeyer, Nov 23 '14 at 19:13

Christian Hujer · Accepted Answer · 2014-11-23T19:17:52.867

3

There are two things that help you:

Generics do not distinguish between Interfaces and Classes.
Generics support ampersand for listing multiple types.

That said, what you probably want is this:

class YourClass<T extends Node & Linkable> {
}

edited Nov 23 '14 at 19:17

answered Nov 23 '14 at 19:11

Christian Hujer

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Tried that, but the class's code only notices the first one (before comma). – DailyFrankPeter Nov 23 '14 at 19:16
There was a bug in my code, I fixed it, please try again. – Christian Hujer Nov 23 '14 at 19:18

java, generics - how to parametrize a class with a type T which BOTH: extends and implements sth

1 Answers1