JDOM2 is a Java library for reading, manipulating, and writing XML documents. Here are some examples of how to use JDOM2 to read and parse XML:

1. Parsing an XML document from a file:

File inputFile = new File("input.xml");
SAXBuilder saxBuilder = new SAXBuilder();
Document document = saxBuilder.build(inputFile);

2. Parsing an XML document from a string:

String xmlString = "<root><element>value</element></root>";
SAXBuilder saxBuilder = new SAXBuilder();
Document document = saxBuilder.build(new StringReader(xmlString));

3. Getting the root element of an XML document:

Element rootElement = document.getRootElement();

4. Getting the value of an element:

String elementValue = rootElement.getChildText("element");

5. Getting the value of an attribute:

String attributeValue = rootElement.getAttributeValue("attribute");

6. Navigating the XML tree using XPath:

XPathFactory xpfac = XPathFactory.instance();
XPathExpression<Element> xp = xpfac.compile("//element", Filters.element());
List<Element> elementList = xp.evaluate(document);

These examples should give you a good idea of how to use JDOM2 to read and parse XML documents in Java.