api/src/main/java/org/apache/commons/graph/Graphs.java

package org.apache.commons.graph;

/*
 * 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 static org.apache.commons.graph.utils.Assertions.checkNotNull;

import org.apache.commons.graph.builder.DefaultLinkedConnectionBuilder;
import org.apache.commons.graph.builder.LinkedConnectionBuilder;

/**
 * The Apache Commons Graph package is a toolkit for managing graphs and graph based data structures.
 */
public final class Graphs
{

    /**
     * Allows populate the given {@link MutableGraph}.
     *
     * @param <V> the Graph vertices type
     * @param <E> the Graph edges type
     * @param <G> the Graph type
     * @param graph the graph has to be populated
     * @return the builder to configure vertices connection
     */
    public static <V, E, G extends MutableGraph<V, E>> LinkedConnectionBuilder<V, E, G> populate( final G graph )
    {
        G checkedGraph = checkNotNull( graph, "Impossible to configure null Graph." );
        return new DefaultLinkedConnectionBuilder<V, E, G>( checkedGraph );
    }

    /**
     * Returns a synchronized (thread-safe) {@link Graph} backed by the specified Graph.
     *
     * It is imperative that the user manually synchronize on the returned graph when iterating over iterable collections:
     * <pre>
     *     Graph syncGraph = synchronize( graph );
     *         ...
     *     synchronized(syncGraph) {
     *         for ( Vertex v : g.getVertices() ) // Must be in synchronized block
     *         {
     *            foo( v )
     *         }
     *   }
     * </pre>
     *
     * Failure to follow this advice may result in non-deterministic behavior.
     *
     * The returned {@link Graph} will be serializable if the specified {@link Graph} is serializable.
     *
     * @param <V> the Graph vertices type
     * @param <E> the Graph edges type
     * @param graph the input {@link Graph}
     * @return the syncronyzed graph
     */
    public static <V, E> Graph<V, E> synchronize( final Graph<V, E> graph )
    {
        Graph<V, E> checkedGraph = checkNotNull( graph, "Impossible to synchronize null Graph." );
        return new SynchronizedGraph<V, E>( checkedGraph );
    }

    /**
     * Returns a synchronized (thread-safe) {@link DirectedGraph} backed by the specified Graph.
     *
     * It is imperative that the user manually synchronize on the returned graph when iterating over iterable collections:
     * <pre>
     *     Graph syncGraph = synchronize( graph );
     *         ...
     *     synchronized(syncGraph) {
     *         for ( Vertex v : g.getVertices() ) // Must be in synchronized block
     *         {
     *            foo( v )
     *         }
     *   }
     * </pre>
     *
     * Failure to follow this advice may result in non-deterministic behavior.
     *
     * The returned {@link Graph} will be serializable if the specified {@link Graph} is serializable.
     *
     * @param <V> the Graph vertices type
     * @param <E> the Graph edges type
     * @param graph the input {@link Graph}
     * @return the syncronyzed graph
     */
    public static <V, E> DirectedGraph<V, E> synchronize( final DirectedGraph<V, E> graph )
    {
        return new SynchronizedDirectedGraph<V, E>( graph );
    }

    /**
     * Returns a synchronized (thread-safe) {@link UndirectedGraph} backed by the specified Graph.
     *
     * It is imperative that the user manually synchronize on the returned graph when iterating over iterable collections:
     * <pre>
     *     Graph syncGraph = synchronize( graph );
     *         ...
     *     synchronized(syncGraph) {
     *         for ( Vertex v : g.getVertices() ) // Must be in synchronized block
     *         {
     *            foo( v )
     *         }
     *   }
     * </pre>
     *
     * Failure to follow this advice may result in non-deterministic behavior.
     *
     * The returned {@link Graph} will be serializable if the specified {@link Graph} is serializable.
     *
     * @param <V> the Graph vertices type
     * @param <E> the Graph edges type
     * @param graph the input {@link Graph}
     * @return the syncronyzed graph
     */
    public static <V, E> Graph<V, E> synchronize( final UndirectedGraph<V, E> graph )
    {
        UndirectedGraph<V, E> checkedGraph = checkNotNull( graph, "Impossible to synchronize null Graph." );
        return new SynchronizedUndirectedGraph<V, E>( checkedGraph );
    }

    /**
     * Returns a synchronized (thread-safe) {@link MutableGraph} backed by the specified Graph.
     *
     * It is imperative that the user manually synchronize on the returned graph when iterating over iterable collections:
     * <pre>
     *     Graph syncGraph = synchronize( graph );
     *         ...
     *     synchronized(syncGraph) {
     *         for ( Vertex v : g.getVertices() ) // Must be in synchronized block
     *         {
     *            foo( v )
     *         }
     *   }
     * </pre>
     *
     * Failure to follow this advice may result in non-deterministic behavior.
     *
     * The returned {@link Graph} will be serializable if the specified {@link Graph} is serializable.
     *
     * @param <V> the Graph vertices type
     * @param <E> the Graph edges type
     * @param graph the input {@link Graph}
     * @return the synchronized graph
     */
    public static <V, E> Graph<V, E> synchronize( final MutableGraph<V, E> graph )
    {
        MutableGraph<V, E> checkedGraph = checkNotNull( graph, "Impossible to synchronize null Graph." );
        return new SynchronizedMutableGraph<V, E>( checkedGraph );
    }

    /**
     * Hidden constructor, this class cannot be instantiated.
     */
    private Graphs()
    {
        // do nothing
    }

}