System.setProperty("http.maxRedirects", "50"); 
          System.getProperties().setProperty("proxySet", "true"); 
          // 如果不设置，只要代理IP和代理端口正确,此项不设置也可以      
         System.getProperties().setProperty("http.proxyHost",“代理ip地址”); 
          System.getProperties().setProperty("http.proxyPort", "代理ip端口号"); 
           
          //确定代理是否设置成功 
          System.out.println(getHtml(" http://iframe.ip138.com/ic.asp"));

          writefile("D:/daili.txt", getHtml("http://iframe.ip138.com/ic.asp")+"\r\n", true);

  public static String getHtml(String address){ 
        StringBuffer html = new StringBuffer(); 
        String result = null; 
        try{ 
            URL url = new URL(address); 
            URLConnection conn = url.openConnection(); 
            conn.setRequestProperty("User-Agent","Mozilla/4.0 (compatible; MSIE 7.0; NT 5.1; GTB5; .NET CLR 2.0.50727; CIBA)"); 
            BufferedInputStream in = new BufferedInputStream(conn.getInputStream()); 
             
            try{ 
                String inputLine; 
                byte[] buf = new byte[4096]; 
                int bytesRead = 0; 
                while (bytesRead >= 0) { 
                    inputLine = new String(buf, 0, bytesRead, "ISO-8859-1"); 
                    html.append(inputLine); 
                    bytesRead = in.read(buf); 
                    inputLine = null; 
                } 
                buf = null; 
            }finally{ 
                in.close(); 
                conn = null; 
                url = null; 
            } 
            result = new String(html.toString().trim().getBytes("ISO-8859-1"), "gb2312").toLowerCase(); 
             
        }catch (Exception e) { 
            e.printStackTrace(); 
            return null; 
        }finally{ 
            html = null;             
        } 
        return result; 
    }