network.addNode(gen.nextInt(NODE_POOL_SIZE));
      }
      ArrayList<Integer> nodeList = new ArrayList<>(network.nodes());
      for (int i = 0; i < NUM_EDGES; ++i) {
        // Parallel edges are allowed, so this should always succeed.
        assertThat(
                network.addEdge(
                    getRandomElement(nodeList, gen), getRandomElement(nodeList, gen), new Object()))
            .isTrue();
      }

                    final Document doc = builder.parse(is);
                    final NodeList nodeList = doc.getElementsByTagName("component");
                    for (int i = 0; i < nodeList.getLength(); i++) {
                        final Node node = nodeList.item(i);
                        final NamedNodeMap attributes = node.getAttributes();
                        if (attributes != null) {

    }

    protected void parseTextContent(final Node node, final StringBuilder buf) {
        if (node.hasChildNodes()) {
            final NodeList nodeList = node.getChildNodes();
            for (int i = 0; i < nodeList.getLength(); i++) {
                final Node childNode = nodeList.item(i);
                parseTextContent(childNode, buf);
            }
        } else if (node.getNodeType() == Node.TEXT_NODE) {

        network.addNode(gen.nextInt(NODE_POOL_SIZE));
      }
      ArrayList<Integer> nodeList = new ArrayList<>(network.nodes());
      for (int i = 0; i < NUM_EDGES; ++i) {
        // Parallel edges are allowed, so this should always succeed.
        assertThat(
                network.addEdge(
                    getRandomElement(nodeList, gen), getRandomElement(nodeList, gen), new Object()))
            .isTrue();
      }

        } catch (final Exception e) {
            throw new CrawlerSystemException("Failed to create XPath instance.", e);
        }
    }

    /**
     *  Use an XPath string to select a nodelist.
     *  XPath namespace prefixes are resolved from the contextNode.
     *
     *  @param contextNode The node to start searching from.
     *  @param expression A valid XPath string.

            final Document doc = builder.parse(is);
            final NodeList snapshotNodeList = doc.getElementsByTagName("snapshot");
            if (snapshotNodeList.getLength() > 0) {
                final NodeList nodeList = snapshotNodeList.item(0).getChildNodes();
                for (int i = 0; i < nodeList.getLength(); i++) {
                    final Node node = nodeList.item(i);

                return new String[] { str.trim() };
            case NODESET:
                final XPathNodes nodeList = (XPathNodes) xObj.value();
                final List<String> strList = new ArrayList<>();
                for (int i = 0; i < nodeList.size(); i++) {
                    final Node node = nodeList.get(i);
                    strList.add(node.getTextContent());
                }

            final StringBuilder buf = new StringBuilder(255);
            final XPathNodes nodeList = getXPathAPI().selectNodeList(document, targetNodePath);
            for (int i = 0; i < nodeList.size(); i++) {
                final Node node = nodeList.get(i);
                buf.append(node.getTextContent()).append(' ');
            }

        buf.append(tag);
        buf.append('>');
    }

    /**
     * {@link NodeList}の文字列表現を追加します。
     *
     * @param children
     *            子要素。{@literal null}であってはいけません
     * @param buf
     *            文字列バッファ。{@literal null}であってはいけません
     */
    public static void appendChildren(final NodeList children, final StringBuilder buf) {
        assertArgumentNotNull("children", children);

                    break;
                case NODESET:
                    final XPathNodes nodeList = (XPathNodes) xObj.value();
                    final List<String> strList = new ArrayList<>();
                    for (int i = 0; i < nodeList.size(); i++) {
                        final Node node = nodeList.get(i);
                        strList.add(node.getTextContent());
                    }