Jung2: how to disable node selfloop

Question

I would like to make a simple graph which is a graph without node's selfloop. In tutorial that is avaiable online it is said that I should use SimpleGraph interface, however it isn't working as it is not found in any jar. Is there something I can do to disable selflooping or should I just for ex. at every mousekey release check if any selfloops are being added and delete such edge which would be highly inefficient.

Answer 1

As said in above point no. 3 your code should look like that:

public class UndirectedSimpleGraph<V,E> extends UndirectedSparseGraph<V,E> {

public UndirectedSimpleGraph(){
    super();
}

public boolean addEdge(E edge, Pair<? extends V> endpoints, EdgeType edgeType){
    Pair<V> new_endpoints = getValidatedEndpoints(edge, endpoints);
    if (new_endpoints == null)
        return false;

    V v1 = new_endpoints.getFirst();
    V v2 = new_endpoints.getSecond();

    if(v1.equals(v2))
        return false;
    else
        return super.addEdge(edge,endpoints,edgeType);
}

Answer 2

I don't know what tutorial that is, but JUNG has no "SimpleGraph" interface.

You can trivially accomplish this yourself, however, via one of these mechanisms:

1. as you suggested: identify that the added edge is a self-loop and remove it
2. once the destination vertex is known, only call addEdge() if source != destination
3. creating a subclass of your preferred graph type that overrides addEdge() and rejects self-loops.

I don't see why you think this is inefficient; any of these checks are O(1).