@Override
  public CacheListener getCacheListener() {
    if (cacheListeners.isEmpty()) {
      return null;
    } else if (cacheListeners.size() == 1) {
      return (CacheListener) cacheListeners.get(0);
    } else {
      throw new IllegalStateException(
          "more than one cache listener exists");
    }
  }
Returns whether or not this <code>RegionAttributesCreation</code> is equivalent to another
<code>RegionAttributes</code>.
geode-core/src/main/java/org/apache/geode/internal/cache/xmlcache/RegionAttributesCreation.java