java xml transform_using javax.xml.transform.Transformer

I'm not understanding what happens to the StreamResult instance. I see that the Transformer object receives source and streamResult:

transformer.transform(source, streamResult);

this transforms source into streamResult? It seems odd that there's nothing returned from this operation yet streamResult now has, for lack of a better word, data. Is it xml data?

package helloWorldSaxon;

import java.io.IOException;

import java.io.StringWriter;

import java.util.Properties;

import java.util.logging.Logger;

import javax.xml.transform.Source;

import javax.xml.transform.Transformer;

import javax.xml.transform.TransformerConfigurationException;

import javax.xml.transform.TransformerException;

import javax.xml.transform.TransformerFactory;

import javax.xml.transform.sax.SAXSource;

import javax.xml.transform.stream.StreamResult;

import org.xml.sax.InputSource;

import org.xml.sax.SAXException;

import org.xml.sax.XMLReader;

import org.xml.sax.helpers.XMLReaderFactory;

public class App {

private static final Logger LOG = Logger.getLogger(App.class.getName());

private final Properties properties = new Properties();

public static void main(String[] args) throws TransformerException, TransformerConfigurationException, IOException, SAXException {

LOG.fine("starting..");

new App().identyTransformOnURL();

}

private void identyTransformOnURL() throws TransformerConfigurationException, TransformerException, IOException, SAXException {

properties.loadFromXML(App.class.getResourceAsStream("/saxon.xml"));

String url = properties.getProperty("url");

StringWriter writer = new StringWriter();

StreamResult streamResult = new StreamResult(writer);

TransformerFactory factory = TransformerFactory.newInstance();

XMLReader xmlReader = XMLReaderFactory.createXMLReader("org.ccil.cowan.tagsoup.Parser");

Source source = new SAXSource(xmlReader, new InputSource(url));

Transformer transformer = factory.newTransformer();

transformer.transform(source, streamResult);

String stringResult = writer.toString();

LOG.info(stringResult);

}

}

I don't understand the JavaDoc on this method:

Transform the XML Source to a Result.

Wouldn't it be more intuitive to return a result?