java教程 - 未知主机异常

Question

I'm trying to read a URL using the tutorial : http://docs.oracle.com/javase/tutorial/networking/urls/readingURL.html

import java.net.*;
import java.io.*;

public class URLReader {
    public static void main(String[] args) throws Exception {

        URL oracle = new URL("http://www.google.com/");
        BufferedReader in = new BufferedReader(new InputStreamReader(oracle.openStream()));
        String inputLine;

        while ((inputLine = in.readLine()) != null)
            System.out.println(inputLine);

        in.close();
    }

}

But I'm getting below exception. www.google.com is a known host ?

Exception in thread "main" java.net.UnknownHostException: www.google.com
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:195)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
    at java.net.Socket.connect(Socket.java:529)
    at java.net.Socket.connect(Socket.java:478)
    at sun.net.NetworkClient.doConnect(NetworkClient.java:163)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:395)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:530)
    at sun.net.www.http.HttpClient.<init>(HttpClient.java:234)
    at sun.net.www.http.HttpClient.New(HttpClient.java:307)
    at sun.net.www.http.HttpClient.New(HttpClient.java:324)
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:970)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:911)
    at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:836)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1172)
    at java.net.URL.openStream(URL.java:1010)
    at URLReader.main(URLReader.java:8)

Answer 1

Are you behind a proxy? Try to set the proxy in eclipse or try

 java -DproxySet=true -DproxyHost=10.0.0.14 -DproxyPort=6588 JavApp

Answer 2

Are you running behind a proxy ? The article seems to suggest there is a configuration needed in that case.

Alternatively, the program might hang or you might see an exception stack trace. If either of the latter two events occurs, you may have to set the proxy host so that the program can find the Oracle server.

Answer 3

我认为它的网络错误检查你的互联网连接....