Dúvida em Streams

import javax.xml.transform.*;
import javax.xml.transform.stream.*;

public class XMLTransformer {

	public static void transform(File xmlFile, File xsltFile) {
		if(!xmlFile.isFile()){
			throw new IllegalAccessError("O arquivo " + xmlFile.getName() + " não existente no local especificado. " + 
					xmlFile.getAbsolutePath());
		}else if(!xsltFile.isFile()){
			throw new IllegalAccessError("O arquivo " + xsltFile.getName() + " não existente no local especificado. " + 
					xsltFile.getAbsolutePath());
		}
		Source xmlSource = new StreamSource(xmlFile);
		Source xsltSource = new StreamSource(xsltFile);
		TransformerFactory transFact = TransformerFactory.newInstance();
		
		try {
			Templates cachedXSLT = transFact.newTemplates(xsltSource);
			Transformer trans = cachedXSLT.newTransformer();
			trans = transFact.newTransformer(xsltSource);
			trans.setOutputProperty(OutputKeys.ENCODING,"UTF-8");
			trans.setOutputProperty(OutputKeys.INDENT, "yes");
			trans.setOutputProperty(OutputKeys.METHOD, "html");
			trans.transform(xmlSource, new StreamResult());
		} catch (TransformerConfigurationException e) {
			e.printStackTrace();
		} catch (TransformerException e) {
			e.printStackTrace();
		}
	}
}