Java code for Graph and its demands

Question

I need to write a graph with some nodes v={1,2,3,4,5,6,7} and edges E={(1-2),(2-3), (3,4),(4-7), (3-6), (2-6), (5-6), (1-5)} and also with some demands D=(s,d)={(1-3),(2-3), (4-5). (7-7), (6-4),(2-7)} which are some path with an exact source an destination for a small network. How can I write this in Java? Can anyone help me please?

Answer 1

Extracting out the nouns you will see that you need a Vertices/Node class, an Edge class and a Demand class. This will be just the beginning of your solution. You will also have a Graph or Network class that consists of a list of Nodes, a list of Edges and a list of Demands. Then you will need to decide where to put the processing methods that use the nodes, edges and demands.

> A Node will consist of an integer. 
> An Edge will consist of two Nodes 
> and so on

Here is an example

public class Node {
   private int nodeNumber;
}

Answer 2

If you don't want to reinvent the weel, you could look into JGraphT. There are some examples available that give you some ideas of how you can use it.

Answer 3

As a start point I can propose you following class structure:

class Vertex{
    String id;
    List<Edge> edges;

    public Vertex(String id){
        this.id = id;
        edges = new ArrayList<Edge>();
    }

    void addEdge(Edge e){
        edges.add(e);
    }
}

class Edge{
   Vertex fromVertex;
   Vertex toVertex;

   Edge(Vertex from, Vertex to){
       this.fromVertex = from;
       this.toVertex = to;
   }
}

etc...

If you consider not to implement your own graph and use it from some library take a look at this question:

Good Java graph algorithm library?