使用java NIO及高速缓冲区写入文件过程解析

byte[] bytes = Files.readAllBytes(Paths.get("E:\\pdf\\aaa\\html\\text.txt").normalize());
    String text = IOUtils.toString(bytes);
    String xml = text.substring(text.indexOf("<tbody>"));
    InputSource inputXML = new InputSource( new StringReader( xml ) );
    XPath xPath = XPathFactory.newInstance().newXPath();
    NodeList nodes = (NodeList) xPath.evaluate("/tbody/tr", inputXML, XPathConstants.NODESET);
    int length = nodes.getLength();
    Path file = Paths.get("E:\\pdf\\aaa\\html\\out.txt");
    try (BufferedWriter writer = Files.newBufferedWriter(file, Charset.defaultCharset(), StandardOpenOption.CREATE)) {
      for (int i = 0; i < length; i++) {
        Node node = nodes.item(i);
        NodeList childList = (NodeList) xPath.evaluate("td", node, XPathConstants.NODESET);
        for (int j = 0; j < childList.getLength(); j++) {
          Node child = childList.item(j);
          String content = child.getTextContent();
          //System.out.print(content);
          writer.write(content);
          if (j <childList.getLength() - 1) {
            writer.write("\t");
          }
        }
        writer.newLine();
      }
    }