Question

我使用了这个示例代码： https://github.com/jgrapht/jgrapht/wiki/DirectedGraphDemo创建有向图。在此示例中，创建的Digraph的顶点为Strings。我需要顶点作为点，我在代码中使用iD指定（iD从0到3，因此它们是int）。所以我修改了这个例子：

public class DirectedGraphDemo {
    public static void graph(int ... iD) {
        // constructs a directed graph with the specified vertices and edges
        DirectedGraph<int, DefaultEdge> directedGraph =
            new DefaultDirectedGraph<int, DefaultEdge>
            (DefaultEdge.class);
        directedGraph.addVertex(0);
        directedGraph.addVertex(1);
        directedGraph.addVertex(2);
        directedGraph.addVertex(3);

        directedGraph.addEdge(0,1);
        directedGraph.addEdge(1,2);
        directedGraph.addEdge(2,3);

        // computes all the strongly connected components of the directed graph
        StrongConnectivityInspector sci =
            new StrongConnectivityInspector(directedGraph);
        List stronglyConnectedSubgraphs = sci.stronglyConnectedSubgraphs();

        // prints the strongly connected components
        System.out.println("Strongly connected components:");
        for (int i = 0; i < stronglyConnectedSubgraphs.size(); i++) {
            System.out.println(stronglyConnectedSubgraphs.get(i));
        }
        System.out.println();

        // Prints the shortest path from vertex 0 to vertex 3. This certainly
        // exists for our particular directed graph.
        System.out.println("Shortest path from 0 to 3:");
        List path =
            DijkstraShortestPath.findPathBetween(directedGraph, 0, 3);
        System.out.println(path + "\n");

    }
}

但是，我在第<：p>行收到错误“unexpected token int”

DirectedGraph<int, DefaultEdge> directedGraph =

我将方法的参数更改为int，为什么我会收到此错误？

Answer 1

您不能将基元类型用作泛型，因此请将其更改为Integer。自动装箱将有效，因此您无需将其他所有内容更改为Integer。

Answer 2

在Java的泛型中，不允许使用诸如int之类的基本类型作为类型参数。作为替代，您可以将Java的包装类型用于基本类型。在这里，您可以使用Integer代替int。

DirectedGraph<Integer, DefaultEdge> directedGraph = // ,...

Java的装箱/取消装箱功能将处理从int到Integer的转换并隐式返回。

将方法参数从String更改为int时出错

2 个答案: