context.write(outKey, new LongWritable(outputValue));
}
});
driver.withKeyGroupingComparator(new FirstCharComparator());
driver.withKeyOrderComparator(new SecondCharComparator());
driver.addInput(new Text("a1"), new LongWritable(1));
driver.addInput(new Text("b1"), new LongWritable(1));
driver.addInput(new Text("a3"), new LongWritable(3));
driver.addInput(new Text("a2"), new LongWritable(2));