Bloksmap.map

[springring]

Hi,
I've been puzzling .

hadoop-0.17.1\src\java\org\apache\hadoop\dfs\Blocksmap.java line 291

  private Map<Block, BlockInfo> map = new HashMap<Block, BlockInfo>();

why is not 
--  private Map<BlockInfo, Block> map = new HashMap<BlockInfo, Block>();

i think if Map<BlockInfo, Block>, the key will be BlockInfo, mean 
{INodeFile,Datanode},
and it can be reduced by INodeFile or/and Datanode.

Springring.Xu