public static String intern(String str) {
    if (str == null) {
      return null;
    }
    return str.intern();
  }
Return the internalized string, or null if the given string is null.
@param str The string to intern
@return The identical string cached in the string pool.
standalone-metastore/metastore-common/src/main/java/org/apache/hadoop/hive/metastore/utils/StringUtils.java