java判断网络连接是否正常

 /**
      * 判断本机当前的网络状态是否联通
      * 在这里主要用到中国天气信息，所以访问百度地址是否能够访问成功来判断当前的网络状态
      */
     public static boolean isConnect() {
         Runtime runtime = Runtime.getRuntime();
         try {
             Process process = runtime.exec("ping " + "www.baidu.com");
             InputStream is = process.getInputStream();
             InputStreamReader isr = new InputStreamReader(is);
             BufferedReader br = new BufferedReader(isr);
             String line = null;
             StringBuffer sb = new StringBuffer();
             while ((line = br.readLine()) != null) {
                 sb.append(line);
             }
             is.close();
             isr.close();
             br.close();

             if (null != sb && !sb.toString().equals("")) {
                 if (sb.toString().indexOf("TTL") > 0) {
                     //网络畅通
                     return true;
                 }
             }
         } catch (Exception e) {
             e.printStackTrace();
         }

         return false;
     }

原文：http://blog.csdn.net/huhui_cs/article/details/8813113