Interface ConcurrentNavigableMap2

src/main/java/org/mapdb/BTreeMapJava.java:1086–1089

    }

    public interface ConcurrentNavigableMap2<K,V> extends ConcurrentNavigableMap<K,V>{
        K firstKey2();
        K lastKey2();
    }

    static protected  class DescendingMap<K,V> extends AbstractMap<K,V> implements  ConcurrentNavigableMap2<K,V> {