Java Coding Problems

Running an asynchronous task and returning a result

User problem: Fetch the order summary of a certain customer.

This time, the asynchronous task must return a result, and so runAsync() is not useful. This is a job for supplyAsync(). It takes Supplier<T> and returns CompletableFuture<T>. T is the type of the result obtained from this supplier via the get() method. In code lines, we can solve this problem as follows:

public static void fetchOrderSummary() {  CompletableFuture<String> cfOrderSummary       = CompletableFuture.supplyAsync(() -> {    logger.info(() -> "Fetch order summary by: "      + Thread.currentThread().getName());    Thread.sleep(500);    return "Order Summary #93443";  });  // wait for summary to be available, this is blocking String summary ...