api/src/main/java/io/sweers/barber/WeakHashSet.java
private void processQueue() {
        WeakElement wv = null;

        while ((wv = (WeakElement) this.queue.poll()) != null) {
            super.remove(wv);
        }
    }
private void processQueue() {
        WeakElement wv = null;

        while ((wv = (WeakElement) this.queue.poll()) != null) {
            super.remove(wv);
        }
    }
Removes all garbage collected values with their keys from the map.
Since we don't know how much the ReferenceQueue.poll() operation
costs, we should call it only in the add() method.