queryIntentActivities(): why 0 used instead of constant?

In code listing 24.3, I’m curious as to why the call to queryIntentActivities

List activities = pm.queryIntentActivities(startupIntent, 0);

uses the value 0 as the argument to the flags parameter instead of one of the constants that are defined in the PackageManager class. None of the constants mentioned in the documentation for that function

(https://developer.android.com/reference/android/content/pm/PackageManager.html#queryIntentActivities(android.content.Intent, int))

has a value of 0. Since queryIntentActivities has been around since API level 1, is it a legacy argument value?

The docs say to use either 0 or some combination of the other flags. I guess they just decided not to create a flag for none. It could be confusing to have a flag for the 0 case since you are intended to combine multiple flags in other cases.

For example, if a none flag existed, something like this wouldn’t make sense:

List activities = pm.queryIntentActivities(startupIntent, NONE|MATCH_UNINSTALLED_PACKAGES);

Just a guess though. I don’t know the answer.