Hadoop MapReduce

Hi,

I'm new to Hadoop and I'm trying to figure out how it works. As for an exercise I should implement something similar to the WordCount-Example. The task is to read in several files, do the WordCount and write and output file for each input file.
Hadoop uses a combiner and shuffles the output of the map-part as an input for the reducer. Then writes one output file (I guess for each instance that is running). I was wondering if it is possible to write one output file for each input file (so keep the words of inputfile1 and write result to outputfile1 and so on). Is it possible to overwrite the Combiner-Class or is there another solution for this (I'm not sure if this should even be solved in a Hadoop-Task but this is the exercise).

Thanks...