question: public CacheSpan touch ( ) { long now = System . currentTimeMillis ( ) ; File newCacheFile = getCacheFileName ( file . getParentFile ( ) , key , position , now ) ; file . renameTo ( newCacheFile ) ; return CacheSpan . createCacheEntry ( key , position , now , newCacheFile ) ; }
target:  Renames the file underlying this cache span to update its last access time.