model/src/main/java/org/apache/commons/graph/model/DirectedMutableGraph.java

package org.apache.commons.graph.model;

/*
 * 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.
 */

import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;

import org.apache.commons.graph.DirectedGraph;
import org.apache.commons.graph.VertexPair;

/**
 * A memory-based implementation of a mutable directed Graph.
 *
 * This class is NOT thread safe!
 *
 * @param <V> the Graph vertices type
 * @param <E> the Graph edges type
 */
public class DirectedMutableGraph<V, E>
    extends BaseMutableGraph<V, E>
    implements DirectedGraph<V, E>
{

    private static final long serialVersionUID = 630111985439492792L;

    private final Map<V, Set<V>> inbound = new HashMap<V, Set<V>>();

    private final Map<V, Set<V>> outbound = new HashMap<V, Set<V>>();

    /**
     * {@inheritDoc}
     */
    public final int getDegree( V v )
    {
        return getInDegree( v ) + getOutDegree( v );
    }

    /**
     * {@inheritDoc}
     */
    public final int getInDegree( V v )
    {
        return inbound.get( v ).size();
    }

    /**
     * {@inheritDoc}
     */
    public final Iterable<V> getInbound( V v )
    {
        return inbound.get( v );
    }

    /**
     * {@inheritDoc}
     */
    public final int getOutDegree( V v )
    {
        return outbound.get( v ).size();
    }

    /**
     * {@inheritDoc}
     */
    public final Iterable<V> getOutbound( V v )
    {
        return outbound.get( v );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void decorateAddVertex( V v )
    {
        inbound.put( v, new LinkedHashSet<V>() );
        outbound.put( v, new LinkedHashSet<V>() );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void decorateRemoveVertex( V v )
    {
        inbound.remove( v );
        outbound.remove( v );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void decorateAddEdge( V head, E e, V tail )
    {
        inbound.get( tail ).add( head );
        outbound.get( head ).add( tail );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void decorateRemoveEdge( E e )
    {
        final VertexPair<V> vertices = getVertices( e );
        inbound.get( vertices.getTail() ).remove( vertices.getHead() );
        outbound.get( vertices.getHead() ).remove( vertices.getTail() );
    }

}