public synchronized int hashCode() {
    mergeBitSet();
    final int prime = 31;
    int result = 1;
    result = prime * result + (int) version;
    result = prime * result + (int) (version >> 32);
    result = prime * result + canonicalExceptions(exceptions).hashCode();
    return result;
  }
returns true if this holder has seen versions that the other holder hasn't
geode-core/src/main/java/org/apache/geode/internal/cache/versions/RegionVersionHolder.java