Method of

base/src/main/java/net/time4j/UnitPatterns.java:232–250

Factory method as constructor replacement. @param lang language setting @return chached instance

(Locale lang)

     * @return  chached instance
     */
    static UnitPatterns of(Locale lang) {

        if (lang == null) {
            throw new NullPointerException("Missing language.");
        }

        UnitPatterns p = CACHE.get(lang);

        if (p == null) {
            p = new UnitPatterns(lang);
            UnitPatterns old = CACHE.putIfAbsent(lang, p);
            if (old != null) {
                p = old;
            }
        }

        return p;

    }

    /**
     * <p>Yields a unit pattern which optionally contains a placeholder