Scan using BLE on a device with an API level of less than 21

Question

I see in the Android API what can be used startLeScan()to scan BLE devices at API levels up to 18. Unfortunately, this method is now outdated, and the recommended alternative startScan(), which is only available at API levels 21+ .

Since API level 21 is only available on Lollipop or higher (about 30% of all devices), I would prefer to use startLeScan()it since it hits most of the devices, but I'm not sure how to go about it. Should I create different implementations for each API level, or is it just impossible to create an application using BLE scanning in versions below Lollipop?