package graph;
public interface WeightedGraph extends Graph {
/**
* Adds a new edge from the vertex from to the vertex to with weight w.
* from and to must already be vertices of this graph.
* If the graph is undirected, then both from is reachable from to over
* an edge with weight w and to is reachable from from over
* an edge with weight w.
* There can be no multiple edges between two vertices, i.e. if there exists already an
* edge between from and to, nothing will be done.
* @param from add a new edge from the vertex from.
* @param to add a new edge to the vertex to.
* @param weight weight of the new edge between from and to.
* @return false if from or to do not exist or
* if there is already an edge from from to to,
* returns true otherwise (edge was successfully added).
*/
public boolean addEdge(Object from, Object to, double w);
/**
* Returns the weight of the edge between the vertex from and to.
* If there is no such vertex or from or to do not
* exist 0.0 will be returned.
* @param from start vertex.
* @param to end vertex.
* @return weight of the edge between the vertex from and to.
*/
public double getEdgeWeight(Object from, Object to);
}