Java tutorial
/* * Created on Oct 18, 2005 * * Copyright (c) 2005, the JUNG Project and the Regents of the University * of California * All rights reserved. * * This software is open-source under the BSD license; see either * "license.txt" or * http://jung.sourceforge.net/license.txt for a description. */ package edu.uci.ics.jung.graph; import java.util.Collection; import java.util.Collections; import java.util.HashMap; import java.util.HashSet; import java.util.Map; import java.util.Set; import org.apache.commons.collections15.Factory; import edu.uci.ics.jung.graph.util.EdgeType; import edu.uci.ics.jung.graph.util.Pair; /** * An implementation of <code>Graph</code> that is suitable for sparse graphs * and permits directed, undirected, and parallel edges. */ @SuppressWarnings("serial") public class SparseMultigraph<V, E> extends AbstractGraph<V, E> implements MultiGraph<V, E> { /** * Returns a {@code Factory} that creates an instance of this graph type. * @param <V> the vertex type for the graph factory * @param <E> the edge type for the graph factory */ public static <V, E> Factory<Graph<V, E>> getFactory() { return new Factory<Graph<V, E>>() { public Graph<V, E> create() { return new SparseMultigraph<V, E>(); } }; } // TODO: refactor internal representation: right now directed edges each have two references (in vertices and directedEdges) // and undirected also have two (incoming and outgoing). protected Map<V, Pair<Set<E>>> vertices; // Map of vertices to Pair of adjacency sets {incoming, outgoing} protected Map<E, Pair<V>> edges; // Map of edges to incident vertex pairs protected Set<E> directedEdges; /** * Creates a new instance. */ public SparseMultigraph() { vertices = new HashMap<V, Pair<Set<E>>>(); edges = new HashMap<E, Pair<V>>(); directedEdges = new HashSet<E>(); } public Collection<E> getEdges() { return Collections.unmodifiableCollection(edges.keySet()); } public Collection<V> getVertices() { return Collections.unmodifiableCollection(vertices.keySet()); } public boolean containsVertex(V vertex) { return vertices.keySet().contains(vertex); } public boolean containsEdge(E edge) { return edges.keySet().contains(edge); } protected Collection<E> getIncoming_internal(V vertex) { return vertices.get(vertex).getFirst(); } protected Collection<E> getOutgoing_internal(V vertex) { return vertices.get(vertex).getSecond(); } public boolean addVertex(V vertex) { if (vertex == null) { throw new IllegalArgumentException("vertex may not be null"); } if (!vertices.containsKey(vertex)) { vertices.put(vertex, new Pair<Set<E>>(new HashSet<E>(), new HashSet<E>())); return true; } else { return false; } } public boolean removeVertex(V vertex) { if (!containsVertex(vertex)) return false; // copy to avoid concurrent modification in removeEdge Set<E> incident = new HashSet<E>(getIncoming_internal(vertex)); incident.addAll(getOutgoing_internal(vertex)); for (E edge : incident) removeEdge(edge); vertices.remove(vertex); return true; } @Override public boolean addEdge(E edge, Pair<? extends V> endpoints, EdgeType edgeType) { Pair<V> new_endpoints = getValidatedEndpoints(edge, endpoints); if (new_endpoints == null) return false; V v1 = new_endpoints.getFirst(); V v2 = new_endpoints.getSecond(); if (!vertices.containsKey(v1)) this.addVertex(v1); if (!vertices.containsKey(v2)) this.addVertex(v2); vertices.get(v1).getSecond().add(edge); vertices.get(v2).getFirst().add(edge); edges.put(edge, new_endpoints); if (edgeType == EdgeType.DIRECTED) { directedEdges.add(edge); } else { vertices.get(v1).getFirst().add(edge); vertices.get(v2).getSecond().add(edge); } return true; } public boolean removeEdge(E edge) { if (!containsEdge(edge)) { return false; } Pair<V> endpoints = getEndpoints(edge); V v1 = endpoints.getFirst(); V v2 = endpoints.getSecond(); // remove edge from incident vertices' adjacency sets vertices.get(v1).getSecond().remove(edge); vertices.get(v2).getFirst().remove(edge); if (directedEdges.remove(edge) == false) { // its an undirected edge, remove the other ends vertices.get(v2).getSecond().remove(edge); vertices.get(v1).getFirst().remove(edge); } edges.remove(edge); return true; } public Collection<E> getInEdges(V vertex) { if (!containsVertex(vertex)) return null; return Collections.unmodifiableCollection(vertices.get(vertex).getFirst()); } public Collection<E> getOutEdges(V vertex) { if (!containsVertex(vertex)) return null; return Collections.unmodifiableCollection(vertices.get(vertex).getSecond()); } // TODO: this will need to get changed if we modify the internal representation public Collection<V> getPredecessors(V vertex) { if (!containsVertex(vertex)) return null; Set<V> preds = new HashSet<V>(); for (E edge : getIncoming_internal(vertex)) { if (getEdgeType(edge) == EdgeType.DIRECTED) { preds.add(this.getSource(edge)); } else { preds.add(getOpposite(vertex, edge)); } } return Collections.unmodifiableCollection(preds); } // TODO: this will need to get changed if we modify the internal representation public Collection<V> getSuccessors(V vertex) { if (!containsVertex(vertex)) return null; Set<V> succs = new HashSet<V>(); for (E edge : getOutgoing_internal(vertex)) { if (getEdgeType(edge) == EdgeType.DIRECTED) { succs.add(this.getDest(edge)); } else { succs.add(getOpposite(vertex, edge)); } } return Collections.unmodifiableCollection(succs); } public Collection<V> getNeighbors(V vertex) { if (!containsVertex(vertex)) return null; Collection<V> out = new HashSet<V>(); out.addAll(this.getPredecessors(vertex)); out.addAll(this.getSuccessors(vertex)); return out; } public Collection<E> getIncidentEdges(V vertex) { if (!containsVertex(vertex)) return null; Collection<E> out = new HashSet<E>(); out.addAll(this.getInEdges(vertex)); out.addAll(this.getOutEdges(vertex)); return out; } @Override public E findEdge(V v1, V v2) { if (!containsVertex(v1) || !containsVertex(v2)) return null; for (E edge : getOutgoing_internal(v1)) if (this.getOpposite(v1, edge).equals(v2)) return edge; return null; } public Pair<V> getEndpoints(E edge) { return edges.get(edge); } public V getSource(E edge) { if (directedEdges.contains(edge)) { return this.getEndpoints(edge).getFirst(); } return null; } public V getDest(E edge) { if (directedEdges.contains(edge)) { return this.getEndpoints(edge).getSecond(); } return null; } public boolean isSource(V vertex, E edge) { if (!containsEdge(edge) || !containsVertex(vertex)) return false; return getSource(edge).equals(vertex); } public boolean isDest(V vertex, E edge) { if (!containsEdge(edge) || !containsVertex(vertex)) return false; return getDest(edge).equals(vertex); } public EdgeType getEdgeType(E edge) { return directedEdges.contains(edge) ? EdgeType.DIRECTED : EdgeType.UNDIRECTED; } @SuppressWarnings("unchecked") public Collection<E> getEdges(EdgeType edgeType) { if (edgeType == EdgeType.DIRECTED) { return Collections.unmodifiableSet(this.directedEdges); } else if (edgeType == EdgeType.UNDIRECTED) { Collection<E> edges = new HashSet<E>(getEdges()); edges.removeAll(directedEdges); return edges; } else { return Collections.EMPTY_SET; } } public int getEdgeCount() { return edges.keySet().size(); } public int getVertexCount() { return vertices.keySet().size(); } public int getEdgeCount(EdgeType edge_type) { return getEdges(edge_type).size(); } public EdgeType getDefaultEdgeType() { return EdgeType.UNDIRECTED; } }