code: @RequiresPermission(Manifest.permission.BLUETOOTH)
  	static void checkAdapterStateOn(@Nullable final BluetoothAdapter adapter) {
  		if (adapter == null || adapter.getState() != BluetoothAdapter.STATE_ON) {
  			throw new IllegalStateException("BT Adapter is not turned ON");
  		}
  	}
docs: Ensure Bluetooth is turned on.
  
  @throws IllegalStateException If {@code adapter} is null or Bluetooth state is not
  {@link BluetoothAdapter#STATE_ON}.