org.jgrapht.graph.AsWeightedGraph Maven / Gradle / Ivy
/* ==========================================
* JGraphT : a free Java graph-theory library
* ==========================================
*
* Project Info: http://jgrapht.sourceforge.net/
* Project Creator: Barak Naveh (http://sourceforge.net/users/barak_naveh)
*
* (C) Copyright 2003-2007, by Barak Naveh and Contributors.
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library; if not, write to the Free Software Foundation,
* Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
*/
/* ----------------------
* AsWeightedGraph.java
* ----------------------
* (C) Copyright 2007, by Lucas J. Scharenbroich and Contributors.
*
* Original Author: Lucas J. Scharenbroich
* Contributor(s): John V. Sichi
*
* $Id: AsWeightedGraph.java 562 2007-09-23 06:44:29Z perfecthash $
*
* Changes
* -------
* 10-Sep-2007 : Initial revision (LJS);
*
*/
package org.jgrapht.graph;
import java.io.*;
import java.util.*;
import org.jgrapht.*;
/**
* A weighted view of the backing graph specified in the constructor. This
* graph allows modules to apply algorithms designed for weighted graphs to an
* unweighted graph by providing an explicit edge weight mapping. The
* implementation also allows for "masking" weights for a subset of the edges in
* an existing weighted graph.
*
* Query operations on this graph "read through" to the backing graph. Vertex
* addition/removal and edge addition/removal are all supported (and immediately
* reflected in the backing graph). Setting an edge weight will pass the
* operation to the backing graph as well if the backing graph implements the
* WeightedGraph interface. Setting an edge weight will modify the weight map in
* order to maintain a consistent graph.
*
* Note that edges returned by this graph's accessors are really just the
* edges of the underlying directed graph.
*
* This graph does not pass the hashCode and equals operations through
* to the backing graph, but relies on Object's equals and
* hashCode methods. This graph will be serializable if the backing
* graph is serializable.
*
* @author Lucas J. Scharenbroich
* @since Sep 10, 2007
*/
public class AsWeightedGraph
extends GraphDelegator
implements Serializable,
WeightedGraph
{
//~ Static fields/initializers ---------------------------------------------
/**
*/
private static final long serialVersionUID = -716810639338971372L;
//~ Instance fields --------------------------------------------------------
protected final Map weightMap;
private final boolean isWeightedGraph;
//~ Constructors -----------------------------------------------------------
/**
* Constructor for AsWeightedGraph.
*
* @param g the backing graph over which a weighted view is to be created.
* @param weightMap A mapping of edges to weights. If an edge is not present
* in the weight map, the edge weight for the underlying graph is returned.
* Note that a live reference to this map is retained, so if the caller
* changes the map after construction, the changes will affect the
* AsWeightedGraph instance as well.
*/
public AsWeightedGraph(Graph g, Map weightMap)
{
super(g);
assert (weightMap != null);
this.weightMap = weightMap;
// Remember whether the backing graph implements the WeightedGraph
// interface
this.isWeightedGraph = (g instanceof WeightedGraph);
}
//~ Methods ----------------------------------------------------------------
/**
* @see WeightedGraph#setEdgeWeight
*/
public void setEdgeWeight(E e, double weight)
{
if (isWeightedGraph) {
super.setEdgeWeight(e, weight);
}
// Always modify the weight map. It would be a terrible violation
// of the use contract to silently ignore changes to the weights.
weightMap.put(e, weight);
}
/**
* @see Graph#getEdgeWeight
*/
public double getEdgeWeight(E e)
{
double weight;
// Always return the value from the weight map first and
// only pass the call through as a backup
if (weightMap.containsKey(e)) {
weight = weightMap.get(e);
} else {
weight = super.getEdgeWeight(e);
}
return weight;
}
}
// End AsWeightedGraph.java