public static void setNumberOfThreads(Job job, int threads) {
    job.getConfiguration().setInt(NUMBER_OF_THREADS, threads);
  }
Set the number of threads in the pool for running maps.
@param job     the job to modify
@param threads the new number of threads
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/MultithreadedTableMapper.java