Java Jung 对象实例化

Question

我正在尝试从 Java Jung Graph 包构建以下内容:EdmondsKarp Object

EdmondsKarpMaxFlow<MyNode, MyLink> alg = new EdmondsKarpMaxFlow<MyNode, MyLink>(g, n2, n5, capTransformer, edgeFlowMap, flowEdgeFactory);

我不知道为什么会出现错误，这是来自 NetBeans 的错误消息:
reason: actual argument org.apache.commons.collections15.Transformer<selfsimilarity.MyLink,java.lang.Double> cannot be converted to org.apache.commons.collections15.Transformer<selfsimilarity.MyLink,java.lang.Number> by method invocation conversion 。

我基本上遵循tutorial .

EdmondsKarpMaxFlow 实例化位于构造函数的底部。在构造函数之后，我将所有参数的代码提供给 EdmondsKarp 对象。这些参数是图、源节点和汇节点、容量变压器、 map 和边缘工厂。

public GraphAlgTests()
    {
        g = new DirectedSparseMultigraph<MyNode, MyLink>();
        // Create some MyNode objects to use as vertices
        MyNode n1 = new MyNode(1); MyNode n2 = new MyNode(2); MyNode n3 = new MyNode(3);  
        MyNode n4 = new MyNode(4); MyNode n5 = new MyNode(5); 
        // Add some directed edges along with the vertices to the graph
        g.addEdge(new MyLink(2.0, 48),n1, n2, EdgeType.DIRECTED); // This method
        g.addEdge(new MyLink(2.0, 48),n2, n3, EdgeType.DIRECTED);
        g.addEdge(new MyLink(3.0, 192), n3, n5, EdgeType.DIRECTED); 
        g.addEdge(new MyLink(2.0, 48), n5, n4, EdgeType.DIRECTED); // or we can use
        g.addEdge(new MyLink(2.0, 48), n4, n2); // In a directed graph the
        g.addEdge(new MyLink(2.0, 48), n3, n1); // first node is the source 
        g.addEdge(new MyLink(10.0, 48), n2, n5);// and the second the destination

        EdmondsKarpMaxFlow<MyNode, MyLink> alg = new EdmondsKarpMaxFlow<MyNode, MyLink>(g, n2, n5, capTransformer, edgeFlowMap, flowEdgeFactory);
    }

public class MyNode 
{
    private int id; // good coding practice would have this as private
    public MyNode(int id) 
    {
        this.id = id;
    }
    public String toString() 
    {                        // Always a good idea for debuging
        return "v"+id;       // JUNG2 makes good use of these.
    }        
}


public class MyLink 
{
    double capacity; // should be private 
    double weight;   // should be private for good practice
    int id;
    int edgeCount = 0;

    public MyLink(double weight, double capacity) 
    {
        this.id = edgeCount++; 
        this.weight = weight;
        this.capacity = capacity;
    } 
    public String toString() 
    { // Always good for debugging
        return "E"+id;
    }
}

   Transformer<MyLink, Double> capTransformer = new Transformer<MyLink, Double>()
   //INFO: Gives the capacity of an edge, denoted here as a "link"
   {
       @Override
       public Double transform(MyLink link)
       {
           return link.capacity;
       }
   };

   Map<MyLink, Double> edgeFlowMap = new HashMap<MyLink, Double>();
   Factory<MyLink> flowEdgeFactory = new Factory<MyLink>()
   {
        @Override
        public MyLink create()
        {
            return new MyLink(1.0, 1.0);
        }
   };

如果还有什么可以帮助的，请告诉我!感谢您的帮助!

Answer 1

它准确地告诉您 Javadocs 是什么对于那个构造函数告诉你:

public EdmondsKarpMaxFlow(DirectedGraph<V,E> directedGraph,
                          V source,
                          V sink,
                          org.apache.commons.collections15.Transformer<E,Number> edgeCapacityTransformer,
                          Map<E,Number> edgeFlowMap,
                          org.apache.commons.collections15.Factory<E> edgeFactory)

您的Transformer是 <MyLink, Double>当需要时<MyLink, Number> (并且需要定义其中的 transform() 方法以返回 Number )

这可能在 API 中的某个时刻发生了更改，并且您正在使用的教程已过时。 API 现在很可能正在调用 doubleValue()关于Number您将返回的对象。

您的 edgeFlowMap 似乎也是如此。以及。