question about SlidingPreReducer.java

[MaGuoWei]

hi guysThere is a function updateCurrent() in this class(SlidingPreReducer).I 
think there is no chance to run the following code in this 
function:currentReduced = reducer.reduce(serializer.copy(currentReduced), 
element);Can any one give me a example that can run this code.  (I have already 
see all the test case)thanks a lot