This keeps the IDs standard throughout the code: either urlString when it
should be a String, or urlString.hashCode() when it should be an int. It
also follows the naming convention in DownloaderService helper methods,
e.g. getIntentFilter(). "create" to me doesn't necessarily mean also "get"
Using @NonNull or @Nullable is fine when it is actually useful, like the
compiler can catch errors, but it also adds a lot of noise when reading the
code. For example, @NonNull here will just make people avoid thinking.
Context can never be null anywhere in Android, that's a given throughout
the Android API. And in this code, urlString is the unique ID used
throughout the process, so if its ever null, nothing works.
dded004321