一種可行的獲取方法，是通過http請求從網站中取出ip欄位。例如：http://ip.chinaz.com/

通過這個網址，加上簡單的正則表示式，即可得到。

public static String getV4IP(){
	String ip = "";
	String chinaz = "http://ip.chinaz.com";
	
	StringBuilder inputLine = new StringBuilder();
	String read = "";
	URL url = null;
	HttpURLConnection urlConnection = null;
	BufferedReader in
 
 = null;
	try {
		url = new URL(chinaz);
		urlConnection = (HttpURLConnection) url.openConnection();
	    in = new BufferedReader( new InputStreamReader(urlConnection.getInputStream(),"UTF-8"));
		while((read=in.readLine())!=null){
			inputLine.append(read+"\r\n");
		}
		//System.out.println(inputLine.toString());
 

	} catch (MalformedURLException e) {
		e.printStackTrace();
	} catch (IOException e) {
		e.printStackTrace();
	}finally{
		if(in!=null){
			try {
				in.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
	
	
	Pattern p = Pattern.compile("\\<dd class\\=\"fz24\">(.*?)\\<\\/dd>"
 
);
	Matcher m = p.matcher(inputLine.toString());
	if(m.find()){
		String ipstr = m.group(1);
		ip = ipstr;
		//System.out.println(ipstr);
	}
	return ip;

}