获取外网IP

package com.apply.controller;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Created by Administrator on 2017/10/18.
 */
public class Demo {
private static final String S = "\\
(.*?)\\<\\/dd>";
    public static void main(String[] args) throws IOException {
        String ip = "";
        String chinaz = "http://ip.chinaz.com";
        StringBuilder builder = new StringBuilder();
        String temp = "";
        HttpURLConnection urlConnection = (HttpURLConnection)new URL(chinaz).openConnection();
        BufferedReader reader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream(), "UTF-8"));
        while ((temp = reader.readLine())!=null){
            builder.append(temp+"\n");
        }
        if (reader != null){
            reader.close();
        }

        Pattern p = Pattern.compile(S);
        Matcher m = p.matcher(builder.toString());
        if(m.find()){
            String ipstr = m.group(1);
            ip = ipstr;
        }
        System.out.println(ip);

    }
}

还有个巨简单的方法

http://ip.chinaz.com/getip.aspx