a-foundation/src/main/java/com/ajjpj/afoundation/collection/immutable/ABTreeMap.java
@SuppressWarnings ("unchecked")
    public static <K, V> ABTreeMap<K, V> empty (ABTreeSpec spec) {
        return new LeafNode (spec, new Object[0], new Object[0]);
    }
@SuppressWarnings ("unchecked")
    public static <K, V> ABTreeMap<K, V> empty (ABTreeSpec spec) {
        return new LeafNode (spec, new Object[0], new Object[0]);
    }
@ SuppressWarnings ( "unchecked" ) public static < K , V > ABTreeMap < K , V > empty ( ABTreeSpec spec ) { return new LeafNode ( spec , new Object [ 0 ] , new Object [ 0 ] ) ; }
intentionally not volatile: This class is immutable, so recalculating per thread works
intentionally not volatile : This class is immutable so recalculating per thread works