Review

setMergeScheduler(MergeScheduler) is synchronized but not getMergeScheduler()

• missing/condition/synchronization

org/apache/lucene/index/IndexWriter.java

getMergeScheduler()

class IndexWriter {
  /**
   * Expert: returns the current MergePolicy in use by this
   * writer.
   * @see #setMergePolicy
   */
  public MergeScheduler getMergeScheduler() {
    ensureOpen();
    return mergeScheduler;
  }

}