false negative writing to response.outputStream

[albfernandez]

	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String badParam = request.getParameter("param");
		Writer out = new PrintWriter(new OutputStreamWriter(response.getOutputStream(), StandardCharsets.UTF_8));
               // Should fire rule violation in next line
		out.write(" <input type='hidden' name='test' value='" + badParam + "' />\n");
		out.close();
	}

It works using PrintWriter but fails using Writer