GPSLocation.java

    double mLatitude = 0.0;
    double mLongitude = 0.0;

    private FusedLocationProviderClient mFusedLocationClient;
    //        mFusedLocationClient = LocationServices.getFusedLocationProviderClient(this);
    //        ^ to be instatiated inside onCreate method

    public void fetchGPS() {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            return;
        }
        mFusedLocationClient.getLastLocation()
                .addOnSuccessListener(this, new OnSuccessListener<Location>() {
                    @Override
                    public void onSuccess(Location location) {
                        // Got last known location. In some rare situations this can be null.
                        if (location != null) {
                            // Logic to handle location object
                            double lat = location.getLatitude();
                            double lon = location.getLongitude();

                            mLatitude = lat;
                            mLongitude = lon;

                        
                    }
                });
    }


    static final int PERMISSIONS_REQUEST_ACCESS_FINE_LOCATION = 2000;
    boolean mLocationPermissionGranted = false;

    private void getLocationPermission() {
        if (ContextCompat.checkSelfPermission(this,
                android.Manifest.permission.ACCESS_FINE_LOCATION)
                == PackageManager.PERMISSION_GRANTED) {
            mLocationPermissionGranted = true;
        } else {
            ActivityCompat.requestPermissions(this,
                    new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION},
                    PERMISSIONS_REQUEST_ACCESS_FINE_LOCATION);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String permissions[], @NonNull int[] grantResults) {
        mLocationPermissionGranted = false;
        switch (requestCode) {
            case PERMISSIONS_REQUEST_ACCESS_FINE_LOCATION: {
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    mLocationPermissionGranted = true;
                    //getDeviceLocation();
                    fetchGPS();
                }
            }
        }
        //  updateLocationUI();
    }

Get and update current location on google maps in android