@Override
  public synchronized Object merge(Object key, Object value, BiFunction remappingFunction) {
    if (interned != null) copyFromInternedToThis();
    return super.merge(key, value, remappingFunction);
  }
**********   Public API of java.util.Hashtable   ***********
common/src/java/org/apache/hadoop/hive/common/CopyOnFirstWriteProperties.java