[Jung-support] [Open Discussion] Unexpected and erroneous effect

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The following forum message was posted by adamjava at http://sourceforge.net/projects/jung/forums/forum/252062/topic/4909974:

Hi,
I remove (iteratively) from the graph all nodes of degree==2 using the method
of graph-derived class:

public int removeDeg2Vertices() {

        int ret;
        ArrayList<GV> tmp = new ArrayList<GV>();
        for(GV v : getVertices()) {

            if (degree(v)==2 ) tmp.add(v);

        }
        ret = tmp.size();
        
        if (0==ret) return 0;
    
        for(GV v : tmp) {

            ArrayList<GV> n = new ArrayList<>();

[b]            if (degree(v)!=2) {
                System.out.println("This line should not display! :( degree
= "+degree(v)+", neighborCount = "+getNeighborCount(v));
                continue;
            }
[/b]
            n.addAll(getNeighbors(v));

            GV v1 = n.get(0);
            GV v2 = n.get(1);

            addEdge(new GE(), v1, v2);

            removeVertex(v);
        }

        return ret;

    }

The problem is that the message "This line should not display" appears on the
screen for some graphs with degree/neighborCount=1. Do you have any idea why?

Thanks in advance
adamjava