@Override
  public int hashCode() {
    int hash = 0;
    Object[] set = hashIndexSetProperties.set;
    for (int i = set.length; i-- > 0;) {
      if (set[i] != null && set[i] != REMOVED) {
        hash += set[i].hashCode();
      }
    }
    return hash;
  }
Locates the next available insertion index for the provided indexKey and set

@return the index of an open or resused position
geode-core/src/main/java/org/apache/geode/cache/query/internal/index/HashIndexSet.java