commons-graph/src/java/org/apache/commons/graph/TraversalOrder.java

package org.apache.commons.graph;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Commons" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Commons", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import org.apache.commons.graph.visitor.Visitor;

/**
 * Class takes a visitor "piggy-backed" and applies it to all nodes
 * and edges.  The traversal order implemented by children of this
 * class may be Depth-first or Breadth-first search, e.g..
 *
 * This relates to the "Strategy" design pattern.
 *
 * @version $Id: TraversalOrder.java,v 1.4 2002/01/16 20:38:28 jvanzyl Exp $
 * @author  <A HREF="http://www.inf.fu-berlin.de/~dahm">M. Dahm</A>
 * @see DFS
 * @see BFS
 * @see Sequential 
*/
public abstract class TraversalOrder 
{
  protected Visitor visitor;
  protected Graph   graph;
  protected boolean stopped;
  protected boolean traverse_complete_graph;

  /**
   * Depth first search algorithm.
   *
   * @param v visitor object to apply when discovering and finishing a vertex or edge
   * @param traverse_all traverse the complete graph or stop after finishing all nodes reachable
   * from the start
   */
  public TraversalOrder(Visitor v, boolean traverse_all) {
    visitor = v;
    traverse_complete_graph = traverse_all;
  }

  public TraversalOrder(Visitor v) {
    this(v, true);
  }

  /**
   * Start traversal.
   *
   * @param g graph to traverse
   * @param start vertex to start at (or null, starts at some vertex then)
   * @param all_vertices visit all vertices or just those reache from start
   */
  public abstract void start(Graph g, Vertex start);

  /** May be called to stop traversal, e.g. if a searched node has been found.
   */
  public void stop() {
    stopped = true;
  }

  /**
   * Depth first search algorithm starting at some vertex.
   *
   * @param g graph to traverse
   */
  public void start(Graph g) {
    start(g, null);
  }
}