hidden classes in package mapred and dfs

[Marko Bauhardt]

Hi all,
i noticed that some classes like

+ DataNodeInfo
+ DFSClient
+ DistributedFileSystem (incl. method getClient())
+ JobInProgress
+ JobProfile
+ JobStatus
+ JobTrackerInfoServer
+ TaskTrackerStatus
are hidden for classes outside the package mapred and dfs. Exists a  
specified reason why this classes are hidden?

Marko