Review

class IndexWriter {
  /** Determines how often segment indices are merged by addDocument().  With
   * smaller values, less RAM is used while indexing, and searches on
   * unoptimized indices are faster, but indexing speed is slower.  With larger
   * values, more RAM is used during indexing, and while searches on unoptimized
   * indices are slower, indexing is faster.  Thus larger values (> 10) are best
   * for batch index creation, and smaller values (< 10) for indices that are
   * interactively maintained.
   *
   * <p>Note that this method is a convenience method: it
   * just calls mergePolicy.setMergeFactor as long as
   * mergePolicy is an instance of {@link LogMergePolicy}.
   * Otherwise an IllegalArgumentException is thrown.</p>
   *
   * <p>This must never be less than 2.  The default value is 10.
   */
  public void setMergeFactor(int mergeFactor) {
    getLogMergePolicy().setMergeFactor(mergeFactor);
  }

}