in java/dataproc-wordcount/src/main/java/com/example/bigtable/sample/CellCounter.java [175:185]
public void reduce(Key key, Iterable<IntWritable> values,
Context context)
throws IOException, InterruptedException {
LOG.warn("Reducing, FTW! ");
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
result.set(sum);
context.write(key, result);
}