@Override
  public Entry<K, V> higherEntry(K key) {
    ArrayHolder<K, V> current = this.holder;
    if (current.getLength() == 0) {
      return null;
    }
    int index = current.find(key);

    // There's a key exactly equal.
    if (index >= 0) {
      index += 1;
    } else {
      index = -(index + 1);
    }

    if (index < current.startIndex || index >= current.endIndex) {
      return null;
    }
    return current.entries[index];
  }
A Map that keeps a sorted array in order to provide the concurrent map interface. Keeping a
sorted array means that it's much more cache line friendly, making reads faster than the tree
version. In order to make concurrent reads and writes safe this does a copy on write. There can
only be one concurrent write at a time.
hbase-common/src/main/java/org/apache/hadoop/hbase/types/CopyOnWriteArrayMap.java