*       RuntimeException} ({@code get} implementations are discouraged from throwing such
   *       exceptions).
   * </ul>
   *
   * <p>The overall principle is to eliminate all checked exceptions: to loop to avoid {@code
   * InterruptedException}, to pass through {@code CancellationException}, and to wrap any exception
   * from the underlying computation in an {@code UncheckedExecutionException} or {@code
   * ExecutionError}.