@Override
  /*
   * return true if no elements exist in the array that are non null or REMOVED tokens
   */
  public boolean isEmpty() {
    return 0 == hashIndexSetProperties.size;
  }
Removes any values in the set which are not contained in <tt>collection</tt>.

@param collection a <code>Collection</code> value
@return true if the set was modified by the retain all operation
geode-core/src/main/java/org/apache/geode/cache/query/internal/index/HashIndexSet.java