How can I prevent the ‘null’ value from being assigned to a non-nullable variable in Dart?

How can I prevent the ‘null’ value from being assigned to a non-nullable variable in Dart? My code is void main() { int? number = null; // Nullable variable

// Using a null check to handle the potential null value int nonNullableNumber = number ?? 0; // Default value is 0 if 'number' is null

print(nonNullableNumber); }