Java 判断是否能外网

方案一：ping

        boolean connect = false;
        Runtime runtime = Runtime.getRuntime();
        Process process;
        try {
            process = runtime.exec("ping " + ipPath);
            InputStream is = process.getInputStream();
            InputStreamReader isr = new InputStreamReader(is,"GBK");
            BufferedReader br = new BufferedReader(isr);
            String line = null;
            StringBuffer sb = new StringBuffer();
            while ((line = br.readLine()) != null) {
                sb.append(line);
            }
            System.out.println("返回值为:"+sb);
            is.close();
            isr.close();
            br.close();
 
            if (null != sb && !sb.toString().equals("")) {
                String logString = "";
                if (sb.toString().indexOf("TTL") > 0) {
                    // OK
                    connect = true;
                } else {
                    // NO OK
                    connect = false;
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println(connect);

方案二:

boolean reachable = InetAddress.getByName("202.108.22.6")
.isReachable(3000);//3s连不上
 System.out.println(reachable);//true:能连/反之不能