org.apache.xmlgraphics.util.dijkstra.DefaultEdgeDirectory Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* $Id: DefaultEdgeDirectory.java 750418 2009-03-05 11:03:54Z vhennebert $ */
package org.apache.xmlgraphics.util.dijkstra;
import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
/**
* Default implementation of an edge directory for the {@link DijkstraAlgorithm}.
*/
public class DefaultEdgeDirectory implements EdgeDirectory {
/** The directory of edges */
private Map edges = new java.util.HashMap();
//Map>
/**
* Adds a new edge between two vertices.
* @param edge the new edge
*/
public void addEdge(Edge edge) {
Map directEdges = (Map)edges.get(edge.getStart());
if (directEdges == null) {
directEdges = new java.util.HashMap();
edges.put(edge.getStart(), directEdges);
}
directEdges.put(edge.getEnd(), edge);
}
/** {@inheritDoc} */
public int getPenalty(Vertex start, Vertex end) {
Map edgeMap = (Map)edges.get(start);
if (edgeMap != null) {
Edge route = (Edge)edgeMap.get(end);
if (route != null) {
int penalty = route.getPenalty();
if (penalty < 0) {
throw new IllegalStateException("Penalty must not be negative");
}
return penalty;
}
}
return 0;
}
/** {@inheritDoc} */
public Iterator getDestinations(Vertex origin) {
Map directRoutes = (Map)edges.get(origin);
if (directRoutes != null) {
Iterator iter = directRoutes.keySet().iterator();
return iter;
}
return Collections.EMPTY_LIST.iterator();
}
/**
* Returns an iterator over all edges with the given origin.
* @param origin the origin
* @return an iterator over Edge instances
*/
public Iterator getEdges(Vertex origin) {
Map directRoutes = (Map)edges.get(origin);
if (directRoutes != null) {
Iterator iter = directRoutes.values().iterator();
return iter;
}
return Collections.EMPTY_LIST.iterator();
}
/**
* Returns the best edge (the edge with the lowest penalty) between two given vertices.
* @param start the start vertex
* @param end the end vertex
* @return the best vertex or null if none is found
*/
public Edge getBestEdge(Vertex start, Vertex end) {
Edge best = null;
Iterator iter = getEdges(start);
while (iter.hasNext()) {
Edge edge = (Edge)iter.next();
if (edge.getEnd().equals(end)) {
if (best == null || edge.getPenalty() < best.getPenalty()) {
best = edge;
}
}
}
return best;
}
}