Eu quero saber o que foi feito quando URL.openconnection ().
Eu fiz um teste como este:

public static void main(String[] args) {
    //    testConnection("http://www.google.com");
    testConnection("http://219.09.34.23.1");
}

private static void testConnection(final String _url) {
    new Thread(new Runnable() {
        String strurl = _url;
        long starttime = 0;
        long endtime = 0;

        public void run() {
            try {
                System.out.println("open:" + strurl);

                starttime = System.currentTimeMillis();
                System.out.println("starttime:" + starttime);

                URL url = new URL(strurl);
                HttpURLConnection conn = (HttpURLConnection) url
                        .openConnection();

                endtime = System.currentTimeMillis();
                System.out.println("openConnection endtime:" + endtime);
                System.out
                        .println("spend:" + (endtime - starttime) + " ms");

                conn.connect();
                endtime = System.currentTimeMillis();
                System.out.println("connect endtime2:" + endtime);
                System.out
                        .println("spend:" + (endtime - starttime) + " ms");

                conn.getResponseCode();
                endtime = System.currentTimeMillis();
                System.out.println("endtime3:" + endtime);
                System.out
                        .println("spend:" + (endtime - starttime) + " ms");
            } catch (MalformedURLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();

                endtime = System.currentTimeMillis();
                System.out.println("MalformedURLException endtime:"
                        + endtime);
                System.out
                        .println("spend:" + (endtime - starttime) + " ms");
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();

                endtime = System.currentTimeMillis();
                System.out.println(" IOException endtime:" + endtime);
                System.out
                        .println("spend:" + (endtime - starttime) + " ms");
            }

        }
    }).start();
}

Quando eu executo o testConnection ("http://www.google.com"), tudo fica bem.
quando eu corro testConnection ("http: //219.09.34.23.1"), "219.09.34.23.1" é um ip aleatório talvez não existe eu escrevi, ele imprime isto:

open:http://219.09.34.23.1
starttime:1338978920350
openconnection endtime:1338978920355
spend:5 ms

    java.net.UnknownHostException: 219.09.34.23.1  
    at java.net.PlainSocketImpl.connect(Unknown Source)  
    at java.net.SocksSocketImpl.connect(Unknown Source)  
    at java.net.Socket.connect(Unknown Source)  
    at java.net.Socket.connect(Unknown Source)  
    at sun.net.NetworkClient.doConnect(Unknown Source)  
    at sun.net.www.http.HttpClient.openServer(Unknown Source)  
    at sun.net.www.http.HttpClient.openServer(Unknown Source)  
    at sun.net.www.http.HttpClient.<init>(Unknown Source)  
    at sun.net.www.http.HttpClient.New(Unknown Source)  
    at sun.net.www.http.HttpClient.New(Unknown Source)  
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)  
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)  
    at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)  
    at Main$1.run(Main.java:37)  
    at java.lang.Thread.run(Unknown Source)

IOException endtime:1338978920393
spend:43 ms

isso significa que gastou 5ms para executar openconnection, e gastou 43ms para descobrir que é um unknownhost, meu problema é, o que foi feito quando o URL.openconnection () como "219.09.34.23.1" é unknownhost? Obrigado por qualquer ajuda!