Difference between close() and disconnect()?

Question

Android Bluetooth Low Energy API implements 1 method to connect to the device connectGatt() but 2 methods to close the connection disconnect() and

Answer 1

With disconnect() you can later call connect() and continue with that cycle.

Once you call close() you are done. If you want to connect again you will have to call connectGatt() on the BluetoothDevice again; close() will release any resources held by BluetoothGatt.