@Override
      public int compare(Entry<K, V> o1, Entry<K, V> o2) {
        return keyComparator.compare(o1.getKey(), o2.getKey());
      }
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