Question: How do I stop a task in Java?

How do I stop being an ExecutorService?

To properly shut down an ExecutorService, we have the shutdown() and shutdownNow() APIs. The shutdown() method doesn’t cause immediate destruction of the ExecutorService. It will make the ExecutorService stop accepting new tasks and shut down after all running threads finish their current work: executorService.

How do you stop an executor thread in Java?


  1. If using Thread directly in your code, you may call interrupt() on the instance of thread.
  2. If using Executor framework, you may cancel each task by calling cancel() on Future.
  3. If using Executor framework, you may shutdown the ExecutorService by calling the shutdownNow() method.

How do you kill an executor’s thread?

When using an Executor, we can shut it down by calling the shutdown() or shutdownNow() methods. Although, it won’t wait until all threads stop executing. Waiting for existing threads to complete their execution can be achieved by using the awaitTermination() method.

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Can a callable task be Cancelled?

When we submit a task (Callable or its cousin Runnable) for execution to an Executor or ExecutorService (e.g. ThreadPoolExecutor), we get a Future back which wraps the tasks. It has a method called Future. cancel(…) which can be used to cancel the task the future wraps. … The task has finished executing.

What happens if we directly call the run () method instead of start () in Java?

The run method is just another method. If you call it directly, then it will execute not in another thread, but in the current thread. If start isn’t called, then the Thread created will never run. The main thread will finish and the Thread will be garbage collected.

What can be submitted to ExecutorService?

3. Submitting tasks to ExecutorService

  • void execute(Runnable task) – executes the given command at some time in the future.
  • Future submit(Runnable task) – submits a runnable task for execution and returns a Future representing that task.

What does thread currentThread () interrupt () do?

currentThread(). interrupt(); allows you to exit out of thread faster, hence when InterruptedException e is caught, the thread is stopped then and there.

What does thread currentThread () return?

currentThread() method returns a reference to the currently executing thread object.

What is thread-safe in Java?

thread-safety or thread-safe code in Java refers to code that can safely be utilized or shared in concurrent or multi-threading environment and they will behave as expected.

Is invokeAll blocking?

Java’s ExecutorService interface defines a method called invokeAll which takes in a Collection of Callable objects to be processed concurrently. However, the invokeAll method itself waits for all of the tasks to finish running before returning, making it a blocking method.

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What is difference between shutdown and shutdownNow?

shutdown() will just tell the executor service that it can’t accept new tasks, but the already submitted tasks continue to run. shutdownNow() will do the same AND will try to cancel the already submitted tasks by interrupting the relevant threads.

What is await termination?

Blocks until all tasks have completed execution after a shutdown request, or the timeout occurs, or the current thread is interrupted, whichever happens first.

How do I get an ExecutorService result?

This can be done by submitting a Callable task to an ExecutorService and getting the result via a Future object. The purpose of the Callable interface is similar to Runnable, but its method returns a value of type T. Integer value = result. get();

What is the difference between future and CompletableFuture?

CompletableFuture is used for asynchronous programming in Java. … A Future is used as a reference to the result of an asynchronous computation. It provides an isDone() method to check whether the computation is done or not, and a get() method to retrieve the result of the computation when it is done.

Is Future cancel blocking?

Method cancel() does not throw exceptions like InterruptedException or ExecutionException. Moreover it has no the variant with timeout. So it looks like, it should NOT be blocking.

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