Java tutorial
/* * Created on Oct 17, 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>DirectedGraph</code>, suitable for sparse graphs, * that permits parallel edges. */ @SuppressWarnings("serial") public class DirectedSparseMultigraph<V, E> extends AbstractTypedGraph<V, E> implements DirectedGraph<V, E>, 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<DirectedGraph<V, E>> getFactory() { return new Factory<DirectedGraph<V, E>>() { public DirectedGraph<V, E> create() { return new DirectedSparseMultigraph<V, E>(); } }; } 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 /** * Creates a new instance. */ public DirectedSparseMultigraph() { super(EdgeType.DIRECTED); vertices = new HashMap<V, Pair<Set<E>>>(); edges = new HashMap<E, Pair<V>>(); } 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 (!containsVertex(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; } public boolean removeEdge(E edge) { if (!containsEdge(edge)) return false; Pair<V> endpoints = this.getEndpoints(edge); V source = endpoints.getFirst(); V dest = endpoints.getSecond(); // remove edge from incident vertices' adjacency sets getOutgoing_internal(source).remove(edge); getIncoming_internal(dest).remove(edge); edges.remove(edge); return true; } public Collection<E> getInEdges(V vertex) { if (!containsVertex(vertex)) return null; return Collections.unmodifiableCollection(getIncoming_internal(vertex)); } public Collection<E> getOutEdges(V vertex) { if (!containsVertex(vertex)) return null; return Collections.unmodifiableCollection(getOutgoing_internal(vertex)); } public Collection<V> getPredecessors(V vertex) { if (!containsVertex(vertex)) return null; Set<V> preds = new HashSet<V>(); for (E edge : getIncoming_internal(vertex)) preds.add(this.getSource(edge)); return Collections.unmodifiableCollection(preds); } public Collection<V> getSuccessors(V vertex) { if (!containsVertex(vertex)) return null; Set<V> succs = new HashSet<V>(); for (E edge : getOutgoing_internal(vertex)) succs.add(this.getDest(edge)); return Collections.unmodifiableCollection(succs); } public Collection<V> getNeighbors(V vertex) { if (!containsVertex(vertex)) return null; Collection<V> neighbors = new HashSet<V>(); for (E edge : getIncoming_internal(vertex)) neighbors.add(this.getSource(edge)); for (E edge : getOutgoing_internal(vertex)) neighbors.add(this.getDest(edge)); return Collections.unmodifiableCollection(neighbors); } public Collection<E> getIncidentEdges(V vertex) { if (!containsVertex(vertex)) return null; Collection<E> incident = new HashSet<E>(); incident.addAll(getIncoming_internal(vertex)); incident.addAll(getOutgoing_internal(vertex)); return incident; } @Override public E findEdge(V v1, V v2) { if (!containsVertex(v1) || !containsVertex(v2)) return null; for (E edge : getOutgoing_internal(v1)) if (this.getDest(edge).equals(v2)) return edge; return null; } @Override public boolean addEdge(E edge, Pair<? extends V> endpoints, EdgeType edgeType) { this.validateEdgeType(edgeType); Pair<V> new_endpoints = getValidatedEndpoints(edge, endpoints); if (new_endpoints == null) return false; edges.put(edge, new_endpoints); V source = new_endpoints.getFirst(); V dest = new_endpoints.getSecond(); if (!containsVertex(source)) this.addVertex(source); if (!containsVertex(dest)) this.addVertex(dest); getIncoming_internal(dest).add(edge); getOutgoing_internal(source).add(edge); return true; } public V getSource(E edge) { if (!containsEdge(edge)) return null; return this.getEndpoints(edge).getFirst(); } public V getDest(E edge) { if (!containsEdge(edge)) return null; return this.getEndpoints(edge).getSecond(); } public boolean isSource(V vertex, E edge) { if (!containsEdge(edge) || !containsVertex(vertex)) return false; return vertex.equals(this.getEndpoints(edge).getFirst()); } public boolean isDest(V vertex, E edge) { if (!containsEdge(edge) || !containsVertex(vertex)) return false; return vertex.equals(this.getEndpoints(edge).getSecond()); } public Pair<V> getEndpoints(E edge) { return edges.get(edge); } public int getEdgeCount() { return edges.size(); } public int getVertexCount() { return vertices.size(); } }