Java Reference
In-Depth Information
List<Integer> requestedIds = ->
.collect(Collectors.toList()); // [4];
} catch (InterruptedException e) {
logger.log(Level.SEVERE, e.getMessage(), e);
private List<Integer> get(Future<List<Integer>> future)
try {
return future.get();
} catch (InterruptedException | ExecutionException
e) {
logger.log(Level.SEVERE, e.getMessage(), e);
return new ArrayList<>();
We start by obtaining an instance of ManagedExecutorService using the @Re-
source annotation [1] . Next, the previously created tasks are injected using the CDI's
Instance<T> class pattern [2] . Thanks to this, the are managed beans and have their
dependencies injected. With the dependencies in place, we use the invokeAll method
[3] of executorService in order to start all our tasks at once (we could also use
multiple calls of the submit method). The return values represent a set of future results,
which can be used to retrieve the collected data when it is ready.
At this point, our tasks are already running so we can simply make a blocking get call on
the future results and wait for the data [4] . When it is ready, we remove any duplicates,
and collect the results in a single list using the flatMap operation. As you remember,
our previous two tasks were waiting 5 seconds each. Thanks to the fact that they are ex-
ecuted simultaneously, we expect that they will both finish after 5 seconds.
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