how to using count() method in xpath with dom4j?

[Kerry]

I want to get the count of node of book:\[code\]<books><book>1</book><book>2</book><book>3</book></books>Document document = null;try{ InputStream in = new FileInputStream(new File("./src/main/java/live.xml")); document = reader.read(in);}catch (Exception e){ e.printStackTrace();}Node node = document.selectSingleNode("count(/books/book)");\[/code\]the exception:\[code\]org.dom4j.XPathException\[/code\]: Exception occurred evaluting XPath: The result of the XPath expression is not a Node. It was: 3.0 of type: java.lang.Double.My question is if I want to use count method in xpath, how to convert Node type to Double type?Thanks.