SPI method to get the available zone IDs.
!(p)
This obtains the IDs that this {@code ZoneRulesProvider} provides.
A provider should provide data for at least one zone ID.
!(p)
The returned zone IDs remain available and valid for the lifetime of the application.
A dynamic provider may increase the set of IDs as more data becomes available.
@return the set of zone IDs being provided, not null
@throws ZoneRulesException if a problem occurs while providing the IDs
SPI method to get the available zone IDs. !(p) This obtains the IDs that this {@code ZoneRulesProvider} provides. A provider should provide data for at least one zone ID. !(p) The returned zone IDs remain available and valid for the lifetime of the application. A dynamic provider may increase the set of IDs as more data becomes available.
@return the set of zone IDs being provided, not null @throws ZoneRulesException if a problem occurs while providing the IDs