code: @Override
      final public boolean containsKey(Object key) {
          ValidateUtility.objectNotNull(key, "key");
          //return get(key) != null;
          return cache.containsCacheId(key);
      }
docs: Returns <tt>true</tt> if this map contains a mapping for the specified
  key.
  
  @param key key whose presence in this map is to be tested.
  @param includeDiskCache true to check the specified key contained in the memory or disk
  maps; false to check the specified key contained in the memory map.
  @return <tt>true</tt> if this map contains a mapping for the specified
  key.
  
  @throws ClassCastException if the key is of an inappropriate type for
  this map.
  @throws NullPointerException if the key is <tt>null</tt> and this map
  does not not permit <tt>null</tt> keys.