如何知道一个连接的资源是否存在和连接会否超时！

java.net.URL l_url = new java.net.URL(sURL);
                    java.net.HttpURLConnection l_connection = (java.net.HttpURLConnection) l_url.openConnection();
                    l_connection.connect();
                    l_urlStream = l_connection.getInputStream();
                    java.io.BufferedReader l_reader = new java.io.BufferedReader(new java.io.InputStreamReader(l_urlStream));
                    String sCurrentLine = "";
                    String sTotalString = "";
                    while ((sCurrentLine = l_reader.readLine()) != null)                    {
                        sTotalString+=sCurrentLine;
                    }