Java中通过代理连接至指定的URL

import java.io.BufferedReader;   
import java.io.IOException;   
import java.io.InputStreamReader;   
import java.net.Authenticator;   
import java.net.InetSocketAddress;   
import java.net.PasswordAuthentication;   
import java.net.Proxy;   
import java.net.URL;   
import java.net.URLConnection;   
import java.util.regex.Matcher;   
import java.util.regex.Pattern;   
  
public class ProxyConnectionTest {   
    public static void main(String[] args) throws IOException {   
        // 设置代理 地址和密码   
        Proxy proxy = new Proxy(Proxy.Type.HTTP,    
                new InetSocketAddress(host, port));   
  
        // 设置代理的密码验证   
        Authenticator auth = new Authenticator() {   
            private PasswordAuthentication pa =    
                new PasswordAuthentication(username, password.toCharArray());   
            @Override  
            protected PasswordAuthentication getPasswordAuthentication() {   
                return pa;   
            }   
        };   
        Authenticator.setDefault(auth);   
           
        // 打开连接   
        System.out.println("connecting...");   
        URL url = new URL("http://www.iteye.com/");   
        URLConnection conn = url.openConnection(proxy);   
  
        // 读取内容   
        InputStreamReader isr = new InputStreamReader(conn.getInputStream());   
        BufferedReader br = new BufferedReader(isr);   
        String line = null;    
        while ((line = br.readLine()) != null) {   
            System.out.println(line);   
        }   
           
        System.out.println("done.");   
    }   
}

然而，这里指定一些URL时总是出现这样那样的错误。比如就无法正常读取http://news.google.com，很多网站的域名后面必须加"/"，如果"http://www.iteye.com/"才能取到内容