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The initialize() method is invoked at runtime, before the MapReduce is executed. Through the getContext() method you can obtain an instance of the MapReduceContext. It allows you to specify datasets to be used as input or output; it . It also provides you access to the actual Hadoop job configuration, as though you were running the MapReduce directly on Hadoop. For example, you can specify the input and output datasets, the mapper and reducer classes as well as the intermediate data format:
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