java获取本机的外网ip

public static String getWebIp() {
		  try {

		   URL url = new URL("http://iframe.ip138.com/ic.asp");

		   BufferedReader br = new BufferedReader(new InputStreamReader(url.openStream()));

		   String s = "";

		   StringBuffer sb = new StringBuffer("");
		   
		   String webContent = "";

		   while ((s = br.readLine()) != null) {
		    sb.append(s + "\r\n");

		   }

		   br.close();
		   webContent = sb.toString();
		   int start = webContent.indexOf("[")+1;
		   int end = webContent.indexOf("]");
		   webContent = webContent.substring(start,end);
		   
		   return webContent;

		  } catch (Exception e) {
		   e.printStackTrace();
		   return "error";

		  }
	}