public Deque<String> getCopyOfDequeByKey(String key) {
        if (key == null)
            return null;

        Map<String, Deque<String>> map = tlMapOfStacks.get();
        if (map == null)
            return null;
        Deque<String> deque = map.get(key);
        if (deque == null)
            return null;

        return new ArrayDeque<String>(deque);
    }
A simple implementation of ThreadLocal backed Map containing values of type 
Deque<String>.

@author Ceki Guuml;c&uuml;
@since 2.0.0
slf4j-api/src/main/java/org/slf4j/helpers/ThreadLocalMapOfStacks.java