code: @SuppressWarnings("unchecked")
      @Override
      public V get(Object key) {
          LinkedHashMapSegment<K, V> seg = segmentFor(key.hashCode());
          try {
              seg.lock.lock();
              return mapEventListener.onGetEntry((K) key, seg.get(key));
          } finally {
              seg.lock.unlock();
          }
  
      }
docs: Returns a value which the specified key is mapped.
  At the same time, this method will call the callback interface, the getting entry event will be triggered.
  
  @param key the key whose associated value is to be returned
  @return the value which the specified key is mapped, or
  {@code null} if this map contains no mapping for the key