@Override
    public boolean containsKey(Object key) {
        return backingMap.containsKey(key); 
//        if (key == null)
//            throw new IllegalArgumentException();
//
//        for (int i = 0; i < entries.size(); i++){
//            ListMapEntry<K,V> entry = entries.get(i);
//            if (keyEq(entry.key, key))
//                return true;
//        }
//        return false;
    }
Implementation of a Map that favors iteration speed rather than
get/put speed.

@author Kirill Vainer
jme3-core/src/main/java/com/jme3/util/ListMap.java