@Override
    public String getShortName() {
      if (shortName != null) return shortName;
      try {
        shortName = ugi.getShortUserName();
        return shortName;
      } catch (Exception e) {
        throw new RuntimeException("Unexpected error getting user short name", e);
      }
    }
Cache value of this instance's {@link #toString()} value. Computing this value is expensive.
Assumes the UGI is never updated. See HBASE-27708.
hbase-common/src/main/java/org/apache/hadoop/hbase/security/User.java