What can be submitted to ExecutorService?

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 is Future multithreading?

Think of a Future as an object that holds the result – it may not hold it right now, but it will do so in the future (once the Callable returns). Thus, a Future is basically one way the main thread can keep track of the progress and result from other threads.

What is FutureTask?

FutureTask is base concrete implementation of Future interface and provides asynchronous processing. It contains the methods to start and cancel a task and also methods that can return the state of the FutureTask as whether it’s completed or cancelled.

How do you use Future tasks?

An example of using Future is working with Thread pools. When one submit a task to ExecutorService which is take a long running time, then it returns a Future object immediately. This Future object can be used for task completion and getting result of computation.

What does ExecutorService shutdown do?

Two different methods are provided for shutting down an ExecutorService. The shutdown() method will allow previously submitted tasks to execute before terminating, while the shutdownNow() method prevents waiting tasks from starting and attempts to stop currently executing tasks.

Why do we use ExecutorService?

The ExecutorService helps in maintaining a pool of threads and assigns them tasks. It also provides the facility to queue up tasks until there is a free thread available if the number of tasks is more than the threads available.

What is a future How is it used in ExecutorService?

Future interface has methods to obtain the result generated by a Callable object and manage its state. It represents the result of an asynchronous computation. The result can only be retrieved using method get() when the computation has completed, blocking if necessary until it is ready.

What is ExecutorService Java?

The Java ExecutorService is the interface which allows us to execute tasks on threads asynchronously. The Java ExecutorService interface is present in the java. util. concurrent package. The ExecutorService helps in maintaining a pool of threads and assigns them tasks.

What is the use of FutureTask in Java?

A FutureTask can be used to wrap a Callable or Runnable object. Because FutureTask implements Runnable , a FutureTask can be submitted to an Executor for execution. In addition to serving as a standalone class, this class provides protected functionality that may be useful when creating customized task classes.

What is a Future How is it used in ExecutorService?

What happens if ExecutorService is not shutdown?

Using ExecutorService shutdown() and awaitTermination​() together. In general, the ExecutorService will not be automatically destroyed when there is not task to process. It will stay alive and wait for new tasks to do. It simply means that JVM will not terminate if we are expecting it to be.

Should we shut down ExecutorService?

Upon termination, an executor has no tasks actively executing, no tasks awaiting execution, and no new tasks can be submitted. An unused ExecutorService should be shut down to allow reclamation of its resources.

What is the use of future object in ExecutorService?

When one submit a task to ExecutorService which is take a long running time, then it returns a Future object immediately. This Future object can be used for task completion and getting result of computation. Examples: Create two task. After one is completely executed, then after waiting 2000 millisecond, second task is being executed

What is FutureTask in Java?

In this tutorial, we will see about Java FutureTask example. FutureTask class has been introduced in JDK 5 with Executor Framework. FutureTask class is the concrete implementation of the Future object and provides methods for start and cancel the task.It also provides method to see if the computation is done or not.

How do I delegate a task to ExecutorService?

There are several ways to delegate a task to ExecutorService: – execute (Runnable) – returns void and cannot access the result. – submit (Runnable or Callable ) – returns a Future object. The main difference is that when submitting Callable , the result can be accessed via the returned Future object.

How to check if an ExecutorService has finished its work?

The second way is by using the isDone () method, which takes a quick look at the Future and checks if it has finished its work or not. ExecutorService represents an abstraction of thread pools and can be created by the utility methods of the Executors class.