Java uses the Dijkstra algorithm and Bellman Ford algorithm of JGraphT to find the shortest path

JGraphT is a graph theory library implemented in Java that provides data structures and algorithms for constructing, manipulating, and analyzing various types of graphs. It supports multiple types of graphs, including directed graphs, undirected graphs, weighted graphs, etc., and provides implementations of many commonly used algorithms, such as Dijkstra algorithm, Bellman Ford algorithm, Kruskal algorithm, Prim algorithm, etc. Maven coordinates: <dependency> <groupId>org.jgrapht</groupId> <artifactId>jgrapht-core</artifactId> <version>1.5.0</version> </dependency> The above is the Maven coordinates of the JGraphT core module, which can be added to the pom.xml file of the project. Next, we will implement an example of using JGraphT's Dijkstra algorithm and Bellman Ford algorithm to find the shortest path, and provide the complete Java code. import org.jgrapht.Graph; import org.jgrapht.GraphPath; import org.jgrapht.alg.interfaces.ShortestPathAlgorithm; import org.jgrapht.alg.shortestpath.BellmanFordShortestPath; import org.jgrapht.alg.shortestpath.DijkstraShortestPath; import org.jgrapht.graph.DefaultDirectedWeightedGraph; import org.jgrapht.graph.DefaultEdge; import java.util.List; public class ShortestPathExample { public static void main(String[] args) { //Create a directed weighted graph Graph<String, DefaultEdge> graph = new DefaultDirectedWeightedGraph<>(DefaultEdge.class); //Add vertices to the graph graph.addVertex("A"); graph.addVertex("B"); graph.addVertex("C"); graph.addVertex("D"); graph.addVertex("E"); //Add edges and weights to the graph graph.addEdge("A", "B"); graph.setEdgeWeight("A", "B", 1); graph.addEdge("A", "C"); graph.setEdgeWeight("A", "C", 4); graph.addEdge("B", "C"); graph.setEdgeWeight("B", "C", 2); graph.addEdge("B", "D"); graph.setEdgeWeight("B", "D", 5); graph.addEdge("C", "D"); graph.setEdgeWeight("C", "D", 1); graph.addEdge("D", "E"); graph.setEdgeWeight("D", "E", 3); //Using Dijkstra Algorithm to Find the Shortest Path ShortestPathAlgorithm<String, DefaultEdge> dijkstra = new DijkstraShortestPath<>(graph); GraphPath<String, DefaultEdge> shortestPathDijkstra = dijkstra.getPath("A", "E"); List<String> vertexListDijkstra = shortestPathDijkstra.getVertexList(); double weightDijkstra = shortestPathDijkstra.getWeight(); System. out. println ("Dijkstra shortest path:"+vertexListDijkstra); System. out. println ("Dijkstra shortest path weight:"+weightDijkstra); //Using the Bellman Ford algorithm to find the shortest path ShortestPathAlgorithm<String, DefaultEdge> bellmanFord = new BellmanFordShortestPath<>(graph); GraphPath<String, DefaultEdge> shortestPathBellmanFord = bellmanFord.getPath("A", "E"); List<String> vertexListBellmanFord = shortestPathBellmanFord.getVertexList(); double weightBellmanFord = shortestPathBellmanFord.getWeight(); System. out. println ("Bellman Ford shortest path:"+vertexListBellmanFord); System. out. println ("Bellman Ford shortest path weight:"+weightBellmanFord); } } The above code first creates a directed weighted graph, then adds the vertices of the graph using the addVertex method, and adds the edges and weights of the graph using the graph.addEdge and graph.setEdgeWeight methods. Next, we use the Dijkstra algorithm and Bellman Ford algorithm to find the shortest path, respectively. By creating corresponding algorithm objects (DijkstraShortestPath and BellmanFordShortestPath) and calling the getPath method, we can obtain the shortest path obtained by the two algorithms, and then print out the weights of the shortest path and the shortest path respectively. Finally, the output example we obtained is: Dijkstra shortest path: [A, B, C, D, E] Dijkstra shortest path weight: 9.0 Bellman Ford shortest path: [A, B, C, D, E] Bellman Ford shortest path weight: 9.0 It can be seen that by using the Dijkstra algorithm and Bellman Ford algorithm provided by the JGraphT library, we can easily solve for the shortest path of a directed weighted graph. Summary: JGraphT is a powerful graph theory library that provides rich data structures and algorithms. It can help developers quickly implement algorithms related to graph theory, such as the shortest path algorithm. In this example, we demonstrated how to use JGraphT's Dijkstra algorithm and Bellman Ford algorithm to solve for the shortest path, and provided the complete Java code.