创建一个内存
PrintWriter使用
StringWriter。您可以从获取底层缓冲区，
StringWriter并在需要时清除它。
StringWriter sr = new StringWriter();PrintWriter w = new PrintWriter(sr);w.print("Some stuff");// Flush writer to ensure that it's not buffering anythingw.flush();// clear stringwritersr.getBuffer().setLength(0);w.print("New stuff");// write to Servlet outw.flush();response.getWriter().print(sr.toString());
