UnsupportedOperationException when using SimpleGraph

[ErrorxCode]

Problem

This is because SimpleGraph does not have explicit relation. So you cannot tell the name of the relationship while adding in the edge, it uses a nameless relation by default.

Solution

Just change ,

Graph<String> graph = new SimpleGraph<>(3);
graph.addEdge("A", "B", "C");

to,

SimpleGraph<String> graph = new SimpleGraph<>(3);
graph.addEdge("A", "B");