code: public TransformTask setNumWriters(int numWriters) {
      Preconditions.checkArgument(numWriters >= 0,
          "Invalid number of reducers: " + numWriters);
      if (numWriters == 0) {
        noCompaction();
      } else {
        this.numWriters = numWriters;
      }
      return this;
    }
docs: Set the number of concurrent writer processes.
  <p>
  If set to 0, this disables compaction.
  
  @param numWriters the number of concurrent writer processes
  @return this for method chaining