jdbc-protolib/src/main/java/com/streamsets/pipeline/lib/jdbc/multithread/util/DirectedGraph.java
public void addDirectedEdge(V vertex1, V vertex2) {
    addVertex(vertex1);
    addVertex(vertex2);
    outwardEdgeVertices.put(vertex1, vertex2);
    inwardEdgesVertices.put(vertex2, vertex1);
  }
public void addDirectedEdge(V vertex1, V vertex2) {
    addVertex(vertex1);
    addVertex(vertex2);
    outwardEdgeVertices.put(vertex1, vertex2);
    inwardEdgesVertices.put(vertex2, vertex1);
  }
Add a directed edge from vertex1 to vertex2 adding those vertices graph (if needed)
@param vertex1 vertex1
@param vertex2 vertex2