why am I getting Error Attempt to invoke virtual method 'double android.location.Location.getLongitude()' on a null object reference - nullpointerexception

Question

the weather forecasting add in this fumction there they are showing error in logcat is longitude and latitude that "
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLongitude()' on a null object reference
at com.example.weatherforecasting.MainActivity.onCreate(MainActivity.java:62)
in that
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
if (ActivityCompat.checkSelfPermission(this , Manifest.permission.ACCESS_FINE_LOCATION)!= PackageManager.PERMISSION_GRANTED &&
ActivityCompat.checkSelfPermission(this,Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(MainActivity.this,new String[]{
Manifest.permission.ACCESS_FINE_LOCATION,Manifest.permission.ACCESS_COARSE_LOCATION},PERMISSION_CODE);
}else {
Location location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
**cityName = getCityName(location.getLongitude(), location.getLatitude());
getWeatherInfo(cityName);**
}
private String getCityName(double longitude , double latitude){
String cityName = "Not found";
Geocoder gcd = new Geocoder(getBaseContext() , Locale.getDefault());
try {
**List<Address> addresses = gcd.getFromLocation(latitude , longitude, 10);**
for (Address adr : addresses){
if (adr!=null){
String city = adr.getLocality();
if (city != null && !city.equals("")){
cityName = city;
}else {
Log.d("TAG", "CITY NOT FOUND");
Toast.makeText(this, "City Not Found", Toast.LENGTH_SHORT).show();
}
}
}
} catch (IOException e) {
e.printStackTrace();
}
return cityName;
}
I tried to adjust but still facing error