About google map in android

Question

public static final int MY_PERMISSIONS_REQUEST_LOCATION = 90;
 public boolean checkLocationPermission(){
 if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED) {


 if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                    Manifest.permission.ACCESS_FINE_LOCATION)) {


                ActivityCompat.requestPermissions(this,
 new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
 MY_PERMISSIONS_REQUEST_LOCATION);


            } else {

                ActivityCompat.requestPermissions(this,
 new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
 MY_PERMISSIONS_REQUEST_LOCATION);
            }
 return false;
        } else {
 return true;
        }
    }

 @Override
 public void onRequestPermissionsResult(int requestCode,
                                           String permissions[], int[] grantResults) {
 switch (requestCode) {
 case MY_PERMISSIONS_REQUEST_LOCATION: {

 if (grantResults.length > 0
 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {


 if (ContextCompat.checkSelfPermission(this,
                            Manifest.permission.ACCESS_FINE_LOCATION)
                            == PackageManager.PERMISSION_GRANTED) {

 if (mGoogleApiClient == null) {
                            buildGoogleApiClient();
                        }
 mMap.setMyLocationEnabled(true);
                    }

                } else {


                    Toast.makeText(this, "permission denied", Toast.LENGTH_LONG).show();
                }
 return;
            }


        }
    }
}

I am new to android in first line why we assignmy_permissions_request_location =90.

 

MY_PERMISSIONS_REQUEST_LOCATION = 90;