After reading: Getting the 'external' IP address in Java
code:
public static void main(String[] args) throws IOException
{
URL whatismyip
Before you run the following code take a look at this: http://www.whatismyip.com/faq/automation.asp
public static void main(String[] args) throws Exception {
URL whatismyip = new URL("http://automation.whatismyip.com/n09230945.asp");
URLConnection connection = whatismyip.openConnection();
connection.addRequestProperty("Protocol", "Http/1.1");
connection.addRequestProperty("Connection", "keep-alive");
connection.addRequestProperty("Keep-Alive", "1000");
connection.addRequestProperty("User-Agent", "Web-Agent");
BufferedReader in =
new BufferedReader(new InputStreamReader(connection.getInputStream()));
String ip = in.readLine(); //you get the IP as a String
System.out.println(ip);
}