anchor.diff:  
   === Defining a Loader
   
  -A loader is defined by implementing the abstract class `CacheLoader`.
  +A loader is defined by implementing the interface `CacheLoader`.
   See the <<getting-started,Getting Started>> example about read through.
   
   [source,java]
  
positive.code: 
  The JavaDoc about the link:{cache2k_docs}/apidocs/cache2k-api/index.html?org/cache2k/io/AdvancedCacheLoader.html[`AdvancedCacheLoader`]
  contains additional details.
  
  === Invalidating
  
  
negative.code: `Cache.containsKey` will not return true when the value exists in the system of authority,
  but only reflects the cache state.
  
  To prevent pitfalls a reduced interface is available: {api_link}/KeyValueSource.html[`KeyValueSource`].
  