code: public static <T extends Serializable> ValueStatistic<T> memoize(long delay, TimeUnit unit, ValueStatistic<T> valueStatistic) {
      return new MemoizingValueStatistic<>(delay, unit, valueStatistic);
    }
docs: Returns a {@link ValueStatistic} that caches the value of a statistic for at least a specific amount of time.
  <p>
  This method does not block.
  <p>
  When the delay expires, if several threads are coming at the same time to read the expired value, then only one will
  do the update and set a new expiring delay and read the new value.
  The other threads can continue to read the current expired value for their next call until it gets updated.
  <p>
  If the caching delay is smaller than the time it takes for a statistic value to be computed, then it is possible that
  a new thread starts asking for a new value before the previous update is completed. In this case, there is no guarantee
  that the cached value will be updated in order because it depends on the time took to get the new value.
  
  @param delay          The delay
  @param unit           The unit of time
  @param valueStatistic The delegate statistic that will provide the value
  @param <T>            The statistic type
  @return the memoizing statistic