code: public String getWifiMacAddress() {
  		WifiManager wifiMan = (WifiManager) context
  				.getSystemService(Context.WIFI_SERVICE);
  		if (wifiMan != null) {
  			WifiInfo wifiInf = wifiMan.getConnectionInfo();
  			return wifiInf.getMacAddress();
  		}
  		return "";
  	}
docs: Returns MAC Address of WiFi Adapter<br>
  Requires READ_PHONE_STATE, ACCESS_NETWORK_STATE and ACCESS_WIFI_STATE
  permissions<br>
  
  @return String representing MAC Address of WiFi Adapter; Empty String in
  some cases such as No WiFi Adapter is installed or WiFi is turned
  off.