Java program for prims algorithm

package ch09; //---------------------------------------------------------------------------// UseGraph.java by Dale/Joyce/Weems Chapter 9 // // Examples of uses of the Graph ADT. //---------------------------------------------------------------------------import ch05.queues.*; import ch03.stacks.*; import ch09.graphs.*; // remove answers. import ch09.priorityQueues.*; import support.Flight; public class UseGraph { private static void shortestPaths(WeightedGraphInterface graph, String startVertex ) // Writes the shortest distance from startVertex to every // other reachable vertex in graph. { Flight flight; Flight saveFlight; // for saving on priority queue int minDistance; int newDistance; PriQueueInterface pq = new Heap(20); // Assume at most 20 vertices String vertex; UnboundedQueueInterface vertexQueue = new LinkedUnbndQueue(); graph.clearMarks(); saveFlight = new Flight(startVertex, startVertex, 0); pq.enqueue(saveFlight); System.out.println("Last Vertex Destination Distance"); System.out.println("------------------------------------"); do { flight = pq.dequeue(); if (!graph.isMarked(flight.getToVertex())) { graph.markVertex(flight.getToVertex()); System.out.println(flight); flight.setFromVertex(flight.getToVertex()); minDistance = flight.getDistance(); vertexQueue = graph.getToVertices(flight.getFromVertex()); while (!vertexQueue.isEmpty()) { vertex = vertexQueue.dequeue(); if (!graph.isMarked(vertex)) { newDistance = minDistance + graph.weightIs(flight.getFromVertex(), vertex); saveFlight = new Flight(flight.getFromVertex(), vertex, newDistance); pq.enqueue(saveFlight); } } } } while (!pq.isEmpty()); System.out.println(); System.out.println("The unreachable vertices are:"); vertex = graph.getUnmarked(); while (vertex != null) { System.out.println(vertex); graph.markVertex(vertex);