User problem: Print a certain customer order.

Since printing is a process that doesn't need to return a result, this is a job for runAsync(). This method can run a task asynchronously and doesn't return a result. In other words, it takes a Runnable object and returns CompletableFuture<Void>; this is shown in the following code:

public static void printOrder() {

  CompletableFuture<Void> cfPrintOrder 
      = CompletableFuture.runAsync(new Runnable() {

    @Override
    public void run() {
      logger.info(() -> "Order is printed by: "
        + Thread.currentThread().getName());
      Thread.sleep(500);
    }
  });

  cfPrintOrder.get(); // block until the order is printed
  logger.info("Customer order was printed ...
");
}

Or, we can write it using a lambda:

public static void printOrder() {

  CompletableFuture<Void> cfPrintOrder 
      = CompletableFuture.runAsync(() -> {

    logger.info(() -> "Order is printed by: "
      + Thread.currentThread().getName());
    Thread.sleep(500);
  });

  cfPrintOrder.get(); // block until the order is printed
  logger.info("Customer order was printed ...
");
}