public static String getDomain(String host) { // See LEP-4602 and LEP-4645. if (host == null) { return null; } // See LEP-5595. if (Validator.isIPAddress(host)) { return host; } int x = host.lastIndexOf(CharPool.PERIOD); if (x <= 0) { return null; } int y = host.lastIndexOf(CharPool.PERIOD, x - 1); if (y <= 0) { return StringPool.PERIOD + host; } int z = host.lastIndexOf(CharPool.PERIOD, y - 1); String domain = null; if (z <= 0) { domain = host.substring(y); } else { domain = host.substring(z); } return domain; }