Re: [jgrapht-users] DefaultEdge vs Void

[J K. <j.k...@gm...>]

Yes that would work. In Java, any class comes with a constructor, whether
you explicitly define it or not. Of course, you would still have to specify
a EdgeFactory which creates new instances of your edges. Aside from that,
it wouldn't really provide you with a benefit. The edge source and target
are stored on the edge. The default types, DefaultEdge or
DefaultWeightedEdge extend IntrustiveEdge. Even if your provide your own
custom edge type which does not extend IntrusiveEdge, under the hood a
Map<YourEdgeType, IntrusiveEdge> will be used which maps your special
YourEdgeType edge  to a newly created IntrusiveEdge. So in summary, you
won't gain anything.

For reference, have a look at AbstractBaseGraph, IntrusiveEdgesSpecifics
(and one of its implementations UniformIntrusiveEdgesSpecifics).

On Sat, Jan 6, 2018 at 1:51 PM, Victor Porton <po...@na...> wrote:

> But what if I write the following?
>
> class MyVoid {
> // empty
> }
>
> Graph<T,MyVoid>
>
> Will this instantiation "work"?
>
> I ask because it seems to me to store source and target in each edge is
> redundant, because in context of its usage the source and target is known.
> I ask therefore, if we can use an empty class like MyVoid to avoid storing
> source and destination.
>
> On Sat, 2018-01-06 at 19:56 +0200, Dimitrios Michail wrote:
>
> Not really. Void is just a placeholder type which cannot be instantiated.
> The type you provide for the edges
> must be a class that can be instantiated.
>
> Read about Java Generics in order to understand its purpose (
> https://docs.oracle.com/javase/tutorial/java/generics/index.html).
>
> There are plenty of examples of graph instantiations in the JGraphT test
> cases.
>
> --Dimitrios
>
>
> On Sat, Jan 6, 2018 at 4:14 PM, Victor Porton <po...@na...> wrote:
>
> What is the difference between Graph<T,DefaultEdge> and Graph<T,Void>?
>
> Does the second work?
>
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