Returns the best-matching language tag using the lookup mechanism defined in RFC 4647.

Parameters:

priorityList		user's Language Priority List in which each language tag is sorted in descending order based on priority or weight
tags		language tangs used for matching

Returns:  the best matching language tag chosen based on priority or weight, or null if nothing matches.

Exceptions:

NullPointerException

if priorityList or tags is null

Since:  1.8