JDOM2和XPath

Question

当我运行以下

XPathFactory xpathFactory = XPathFactory.instance();
XPathExpression<Double> query =
xpathFactory.compile("count(1)", Filters.fdouble());
List<Double> result = query.evaluate(new Element("test"));

但是评估失败：

无法评估表达式。 查看原因原因：功能：count

那是个胡说八道的例子，但是我想要一些自我包含的东西。 这有什么问题？

Answer 1

如果要计算test元素的数量，请尝试此操作；

Element root = new Element("test");
Document doc = new Document(root);

XPathFactory xpathFactory = XPathFactory.instance();
XPathExpression<Double> query = xpathFactory.compile("count(//test)", Filters.fdouble());
List<Double> result = query.evaluate(doc);