Re: Directed Acyclic Graph implementation

Hi Jens,

Thanks for the prompt response.

I was playing with jgrapht for a couple of hours -

In the file org.jgrapht.graph.AbstractBaseGraph.java (which extends AbstractGraph)
            AbstractBaseGraph<V, E> newGraph =
                TypeUtil.uncheckedCast(super.clone(), typeDecl);

In the file org.jgrapht.graph.AbstractGraph.java

public abstract class AbstractGraph<V, E>
    implements Graph<V, E>

 - there is no clone() implementation - so the compiler looks for Object.clone

Also in the file org.jgrapht.graph.IntrusiveEdge.java

class IntrusiveEdge
    implements Cloneable,
        Serializable
{
/**
     * @see Object#clone()
     */
    public Object clone()
    {
        try {
            return super.clone();
        } catch (CloneNotSupportedException e) {
            // shouldn't happen as we are Cloneable
            throw new InternalError();
        }
    }
}

Again - the compiler looks for Object.clone

So, I implemented a clone() in AbstractGraph.java &  IntrusiveEdge.java

And finally I hit :- ClassBasedEdgeFactory.java

private final Class<? extends E> edgeClass;

.
.
public E createEdge(V source, V target)
    {
        try {
            return edgeClass.newInstance();
           
        } catch (Exception ex) {
            throw new RuntimeException("Edge factory failed", ex);
        }
    }

At this point :- I looked for some other graph library. :(

Maybe I am doing something wrong.. any pointers is helpful.

Regards

On Thursday, September 12, 2013 4:06:03 PM UTC-4, Jens wrote:

I am looking for an implementation of a Directed Graph for my GWT project - came across jgrapht - but porting it to GWT with all "CloneNotSupportedException" / "Object.clone()" / "newInstance()"  issues proved to be troublesome.

Looks like JGraphT does not use newInstance() in the library itself, only in a test case. GWT trunk already emulates CloneNotSupportedException so implementing clone() methods would also work. But be aware that GWT does not provide an implementation of Object.clone() so at some point you must create the instance on your own instead of calling super.clone(). 

But maybe you don't even need to emulate clone() because the only library class that calls .clone() is an adapter class for JGraph <-> JGraphT living outside of jgrapht-core.

So I think jgrapht-core can made GWT ready without major issues.

Search ".newInstance()": https://github.com/jgrapht/jgrapht/search?q=.newInstance%28%29&type=Code

Search ".clone()": https://github.com/jgrapht/jgrapht/search?q=.clone%28%29&type=Code

-- J.

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