java - 添加两条边 - JGraphT

Question

我正在使用SimpleDirectedWeightedGraph来自JGrapghT 1.2.0图书馆。我的目标是在顶点 A 之间创建两条边和B这样A <-80-> B 。如果我这样做:

graph.addEdge("A", "B", 80);
graph.addEdge("B", "A", 80);
System.out.println(graph.getAllEdges("A", "B"));
System.out.println(graph.getAllEdges("B", "A"));

我得到:

[80]
[]

如果我将第二行更改为: graph.addEdge("B", "A", 81); ，我明白

[80]
[81]

为什么我不能在具有相同值的顶点之间创建两条边？

Answer 1

来自JavaDocs在SimpleDirectedGraph上:

A simple directed graph. A simple directed graph is a directed graph in which neither multiple (parallel) edges between any two vertices nor loops are permitted.