IP-Converters

/**
 * Utils which  helps work with ip
 * generate own ip
 * convert ip to tiny url
 * convert tiny url to ip
 * change ip form
 */
public class Utils {
    // Key for encrypt && decrypt decimal ip to tiny url
    static String key = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

    /**
     * @return device's ip in short link form
     */
    public static String getOwnShortLink() {
        return ipToTinyUrl(getIp());
    }

    /**
     * @param ip - generated in {@link #getIp()}
     * @return decimal ip
     */
    public static long convertIpToLong(String ip) {
        return Integer.parseInt(ip.split("\\.")[0]) * 16777216L
                + Integer.parseInt(ip.split("\\.")[1]) * 65536L
                + Integer.parseInt(ip.split("\\.")[2]) * 256L
                + Integer.parseInt(ip.split("\\.")[3]);
    }

    /**
     * @param shortLink - generated in {@link #ipToTinyUrl(String)}
     * @return ip from short link
     */
    public static String getIpFromShortLink(String shortLink) {
        return convertLongToIp(tinyUrlToIp(shortLink));
    }

    /**
     * @param decimalIp - ip in decimal form
     * @return ip in string form
     */
    public static String convertLongToIp(long decimalIp) {
        return decimalIp / 16777216L // 256^3
                + "."
                + decimalIp % 16777216L / 65536L // 256^2
                + "."
                + decimalIp % 16777216L % 65536L / 256L // 256^1
                + "."
                + decimalIp % 16777216L % 65536L % 256L; // 256^0
    }

    /**
     * @return computer's ip
     */
    public static String getIp() {
        String ipAddress = null;
        Enumeration<NetworkInterface> net = null;
        try {
            net = NetworkInterface.getNetworkInterfaces();
        } catch (SocketException e) {
            e.printStackTrace();
        }
        assert net != null;
        while (net.hasMoreElements()) {
            NetworkInterface element = net.nextElement();
            Enumeration<InetAddress> addresses = element.getInetAddresses();
            while (addresses.hasMoreElements()) {
                InetAddress ip = addresses.nextElement();
                if (ip instanceof Inet4Address && ip.isSiteLocalAddress()) {
                    ipAddress = ip.getHostAddress();
                }
            }
        }
        return ipAddress;
    }

    /**
     * @param ip - generated in {@link #getIp()}
     * @return tiny url
     */
    public static String ipToTinyUrl(String ip) {
        long decimalIp = convertIpToLong(ip);
        StringBuilder tinyUrl = new StringBuilder();
        while (decimalIp > 0) {
            tinyUrl.append(key.charAt((int) (decimalIp % 62)));
            decimalIp /= 62;
        }
        return tinyUrl.reverse().toString();
    }


    /**
     * @param tinyUrl - get tiny Url created in {@link #ipToTinyUrl(String)}
     * @return decimal ip
     */
    public static long tinyUrlToIp(String tinyUrl) {
        long ip = 0;
        for (int i = 0; i < tinyUrl.length(); i++) {
            ip = (ip * 62) + key.indexOf(tinyUrl.charAt(i));
        }
        return ip;
    }
}