java.net.UnknownHostException:www.google.com

我正在开发一个健全性检查网络应用程序。我尝试使用 HttpUrlConnection 方法获取 url 响应，但收到 UnknownHostException。

 System.setProperty("java.net.preferIPv4Stack" , "true");
    String[] uat_targetUrls={"https://www.google.com"};
    String[] uat_targetResponse=new String[uat_targetUrls.length];

            HttpURLConnection httpUrlConn;
            httpUrlConn = (HttpURLConnection) new URL(uat_targetUrls[i])
            .openConnection();

            httpUrlConn.setRequestMethod("GET");


            httpUrlConn.setConnectTimeout(30000);
            httpUrlConn.setReadTimeout(30000);



           if(httpUrlConn.getResponseCode()==200)
               uat_targetResponse[i]="UP";
           else 
               uat_targetResponse[i]="DOWN";

执行此操作时，我收到各种 url 的 UnknownHostException。谁可以帮我这个事。我正在使用 Eclipse IDE。这是我收到的错误：

java.net.UnknownHostException: www.google.com
    at java.net.PlainSocketImpl.connect(Unknown Source)
    at java.net.SocksSocketImpl.connect(Unknown Source)

Thanks.

问题一定是您机器上的网络问题。

您的代码对我有用（通过一些小修复来修复丢失的循环变量i):

public static void main(String[] args) throws Exception {
    System.setProperty("java.net.preferIPv4Stack", "true");
    String[] uat_targetUrls = { "https://www.google.com" };
    String[] uat_targetResponse = new String[uat_targetUrls.length];

    HttpURLConnection httpUrlConn;
    httpUrlConn = (HttpURLConnection) new URL(uat_targetUrls[0])
            .openConnection();

    httpUrlConn.setRequestMethod("GET");

    httpUrlConn.setConnectTimeout(30000);
    httpUrlConn.setReadTimeout(30000);

    if (httpUrlConn.getResponseCode() == 200)
        uat_targetResponse[0] = "UP";
    else
        uat_targetResponse[0] = "DOWN";


    System.out.println(uat_targetResponse[0]);
}

Output: UP