String dirname = "C:/eclipse/workspace/Sample/";
	File outputFilepath= new File(dirname);
	transformer.transform(new StreamSource("books.xml"),
new StreamResult(outputFilepath));

You can't write to a directory. I mean: the code above
wont create a new file in the directory, it is interpreted
as an attepmt to change the data which makes up the directory
description itself. Try
 	String dirname = "C:/eclipse/workspace/Sample/";
 	File outputFilepath= new File(dirname+"somefile.xml");
 	transformer.transform(new StreamSource("books.xml"),
 new StreamResult(outputFilepath));
instead.