How to force locale for String format for the whole app in Android?

I know that String has a format method which takes Locale as a parameter. I would like to ask if there is a way to force or apply a certain locale to all String formats in the whole app?

I tried resConfigs in Gradle but it seems to only work for language, not region. For example, I tried en_AU locale on a device with Germany English but it does not display the strings in Australian English.