The XMLInputFactory is a factory class in Java's StAX (Streaming API for XML) API that creates instances of XMLStreamReader, which is used to read XML documents in a streaming fashion. The XMLInputFactory allows you to create XMLStreamReader objects from various input sources such as InputStreams, Readers, and URLs.

Here's an example of using the XMLInputFactory to create an XMLStreamReader from an InputStream:

import javax.xml.stream.*;
import java.io.*;

public class StAXExample {

    public static void main(String[] args) throws Exception {
        InputStream inputStream = new FileInputStream("example.xml");
        XMLInputFactory factory = XMLInputFactory.newInstance();
        XMLStreamReader reader = factory.createXMLStreamReader(inputStream);
        while (reader.hasNext()) {
            int event = reader.next();
            if (event == XMLStreamConstants.START_ELEMENT) {
                System.out.println("Start Element: " + reader.getLocalName());
            } else if (event == XMLStreamConstants.CHARACTERS) {
                System.out.println("Text: " + reader.getText());
            } else if (event == XMLStreamConstants.END_ELEMENT) {
                System.out.println("End Element: " + reader.getLocalName());
            }
        }
        reader.close();
    }
}

In this example, we create an InputStream object from an input XML file using a FileInputStream. We then create an XMLInputFactory object using the newInstance() method, which we use to create an XMLStreamReader object by passing in the InputStream object to the createXMLStreamReader() method.

We then read the XML document using a while loop that iterates through each event in the document using the next() method of the XMLStreamReader. We print out the type of each event (e.g. START_ELEMENT, CHARACTERS, END_ELEMENT) and the corresponding element or text using the getLocalName() and getText() methods.

Finally, we close the reader using the close() method.

Note that the XMLStreamReader interface provides a low-level, event-based API for reading XML documents, which may be more difficult to use than the higher-level, object-oriented DOM (Document Object Model) API or the SAX (Simple API for XML) API. However, StAX is generally more memory-efficient than the DOM API and faster than the SAX API for large documents, making it a good choice for certain types of applications.