Pre Marshmallow my app would obtain it\'s device MAC address via BluetoothAdapter.getDefaultAdapter().getAddress().
Now with Marshmallow Android is retu
Worked great
 private String getBluetoothMacAddress() {
        BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        String bluetoothMacAddress = "";
        try {
            Field mServiceField = bluetoothAdapter.getClass().getDeclaredField("mService");
            mServiceField.setAccessible(true);
            Object btManagerService = mServiceField.get(bluetoothAdapter);
            if (btManagerService != null) {
                bluetoothMacAddress = (String) btManagerService.getClass().getMethod("getAddress").invoke(btManagerService);
            }
        } catch (NoSuchFieldException | NoSuchMethodException | IllegalAccessException | InvocationTargetException ignore) {
        }
        return bluetoothMacAddress;
    }