E addEdge(V jtSource, V jtTarget) { E jtEdge = graph.getEdgeFactory().createEdge(jtSource, jtTarget); jtElementsBeingAdded.add(jtEdge); boolean added = graph.addEdge(jtSource, jtTarget, jtEdge); jtElementsBeingAdded.remove(jtEdge); return added ? jtEdge : null; }