@Mapper public class MyMapper extends Mapper<LongWritable, Text, Text, IntWritable> { // ... } @Reducer public class MyReducer extends Reducer<Text, IntWritable, Text, IntWritable> { // ... } @InputFormat(TextInputFormat.class) @OutputFormat(TextOutputFormat.class) public class MyMapReduceJob { // ... } @Partitioner(MyPartitioner.class) public class MyMapReduceJob { // ... }