public static <K, V> boolean removeAllHelper(Map<K, V> map, Collection<?> collection) {
        int oldSize = map.size();
        Iterator<?> it = collection.iterator();
        while (it.hasNext()) {
            map.remove(it.next());
        }
        return oldSize != map.size();
    }
Helper for writing standard Java collection interfaces to a data
structure like {@link ArrayMap}.
android/android_framework/base/src/main/java/github/tornaco/android/thanos/core/util/collection/MapCollections.java