Planned lessonMID-003-L03

Executors and futures

Lesson 3 of 7
Mid-level

On This Lesson 4 topics

In this lesson
Planned topics
Draft outline details
Practice

This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.

In this lesson

submit tasks and collect results.

Planned topics

ExecutorService separates submitting a task from how it runs.
Runnable returns nothing; Callable<V> returns a value and may throw.
submit returns a Future<V>; get() blocks, optionally with a timeout.
ExecutionException wraps the task's exception; the cause is inside.
invokeAll runs a batch and returns when all finish.

Draft outline details

Demonstration

java

ExecutorService pool = Executors.newFixedThreadPool(4);
Future<BigDecimal> f = pool.submit(() -> supplier.fetchPrice(sku));
BigDecimal price = f.get(2, TimeUnit.SECONDS);

Check your understanding

Where does a task's exception surface?

Show answer

In Future.get(), wrapped in ExecutionException.

Practice

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