return g;
        }

        List<MetadataGraphVertex> visited = new ArrayList<>(g.getVertices().size());
        visit(g.getEntry(), visited, g);

        List<MetadataGraphVertex> dropList = new ArrayList<>(g.getVertices().size());

        // collect drop list
        for (MetadataGraphVertex v : g.getVertices()) {
            if (!visited.contains(v)) {
                dropList.add(v);
            }
        }

abstract class TypeVisitor {

  private final Set<Type> visited = Sets.newHashSet();

  /**
   * Visits the given types. Null types are ignored. This allows subclasses to call {@code
   * visit(parameterizedType.getOwnerType())} safely without having to check nulls.
   */
  public final void visit(@Nullable Type... types) {
    for (Type type : types) {
      if (type == null || !visited.add(type)) {
        // null owner type, or already visited;

   *
   * Visited Nodes = {}
   * EndpointPair [N1, N2] - return
   * EndpointPair [N1, N3] - return
   * Visited Nodes = {N1}
   * EndpointPair [N2, N1] - skip
   * EndpointPair [N2, N3] - return
   * Visited Nodes = {N1, N2}
   * EndpointPair [N3, N1] - skip
   * EndpointPair [N3, N2] - skip
   * Visited Nodes = {N1, N2, N3}
   * EndpointPair [N4, N4] - return
   * Visited Nodes = {N1, N2, N3, N4}

    fun visitTree(
        classDetails: ClassDetails,
        classesDir: File,
        jarOutputStream: JarOutputStream,
        visited: MutableSet<ClassDetails>
    ) {

        if (!visited.add(classDetails)) {
            return
        }
        if (classDetails.visited) {
            val fileName = classDetails.outputClassFilename
            val classFile = classesDir.resolve(fileName)

        visit(t.getActualTypeArguments());
      }

      @Override
      void visitTypeVariable(TypeVariable<?> t) {
        visit(t.getBounds());
      }
    }.visit(type);
  }

  private static void assertVisited(Type type) {
    TypeVisitor visitor = new BaseTypeVisitor();
    try {
      visitor.visit(type);
      fail("Type not visited");

import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

class Graph {
    private enum DfsState {
        VISITING,
        VISITED
    }

    final Map<String, Vertex> vertices = new LinkedHashMap<>();

    public Vertex getVertex(String id) {
        return vertices.get(id);
    }

    public Collection<Vertex> getVertices() {

        ClasspathContainer cpc;

        List<MetadataGraphVertex> visited;

        // -----------------------------------------------------------------------
        protected ClasspathGraphVisitor(MetadataGraph cleanGraph, ClasspathContainer cpc) {
            this.cpc = cpc;
            this.graph = cleanGraph;

            visited = new ArrayList<>(cleanGraph.getVertices().size());
        }

        final CrawlerContext crawlerContext = CrawlingParameterUtil.getCrawlerContext();
        final UrlQueueService<UrlQueue<?>> urlQueueService = CrawlingParameterUtil.getUrlQueueService();
        if (!urlQueueService.visited(urlQueue)) {
            if (checkAccessCount(crawlerContext)) {
                final AccessResult<?> accessResult = createAccessResult(responseData, resultData);
                if (logger.isDebugEnabled()) {

                        "Edge between '" + from + "' and '" + to + "' introduces to cycle in the graph", cycle);
            }
        }
    }

    private enum DfsState {
        VISITING,
        VISITED
    }

    private static List<String> visitCycle(
            Map<String, Set<String>> graph,
            Collection<String> children,
            Map<String, DfsState> stateMap,

    public void saveSession(final String sessionId) {
        // NOP
    }

    /*
     * (non-Javadoc)
     *
     * @see org.codelibs.fess.crawler.service.UrlQueueService#visited(UrlQueue)
     */
    @Override
    public boolean visited(final UrlQueueImpl<Long> urlQueue) {
        final Queue<UrlQueueImpl<Long>> urlQueueList = dataHelper.getUrlQueueList(urlQueue.getSessionId());
        synchronized (urlQueueList) {