How do I set up an ExecutorService?

How do I set up an ExecutorService?

The easiest way to create ExecutorService is to use one of the factory methods of the Executors class. For example, the following line of code will create a thread pool with 10 threads: ExecutorService executor = Executors. newFixedThreadPool(10);

How do I wait for ExecutorService to finish?

ExecutorService – Waiting for Threads to Finish

1. Waiting for existing threads to complete their execution can be achieved by using the awaitTermination() method.
2. A CountDownLatch is useful when we need a mechanism to notify one or more threads that a set of operations performed by other threads has finished.

What is the difference between executor and ExecutorService?

Executor just executes stuff you give it. ExecutorService adds startup, shutdown, and the ability to wait for and look at the status of jobs you’ve submitted for execution on top of Executor (which it extends).

What can be submitted to ExecutorService?

Submit Runnable The Java ExecutorService submit(Runnable) method also takes a Runnable implementation, but returns a Future object. This Future object can be used to check if the Runnable has finished executing.

Why do we need ExecutorService?

ExecutorService abstracts away many of the complexities associated with the lower-level abstractions like raw Thread . It provides mechanisms for safely starting, closing down, submitting, executing, and blocking on the successful or abrupt termination of tasks (expressed as Runnable or Callable ).

How do I submit mock to ExecutorService?

We can mock executor service call using the following code snippet. when(executorService. submit(any(Callable. class))) .

Do we need to close ExecutorService?

When finished using an ExecutorService , you need to shut it down explicitly. From its javadoc: “An unused ExecutorService should be shut down to allow reclamation of its resources.” Calling shutdown initiates a gradual and orderly shutdown.

What does ExecutorService shutdown do?

Shutting down the ExecutorService shutdown() – when shutdown() method is called on an executor service, it stops accepting new tasks, waits for previously submitted tasks to execute, and then terminates the executor. shutdownNow() – this method interrupts the running task and shuts down the executor immediately.

What is the use of 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 ExecutorService and thread pool?

To use thread pools, we first create a object of ExecutorService and pass a set of tasks to it. ThreadPoolExecutor class allows to set the core and maximum pool size. The runnables that are run by a particular thread are executed sequentially. Thread Pool Initialization with size = 3 threads.

How do you measure a thread pool?

Just give me the formula!

1. Number of threads = Number of Available Cores * (1 + Wait time / Service time)
2. Number of threads = Number of Available Cores * Target CPU utilization * (1 + Wait time / Service time)
3. 22 / 0.055 = 400 // the number of requests per second our service can handle with a stable response time.

Is the uncaughtexceptionhandler called with an ExecutorService?

When I create the thread manually (i.e. by instantiating java.lang.Thread) the UncaughtExceptionHandler is called appropriately. However, when I use an ExecutorService with a ThreadFactory the handler is ommited.

Why is the uncaughtexceptionhandler not working?

The reason the UncaughtExceptionHandler doesn’t work as expected is not because the internal worker swallows exceptions. The reason it doesn’t work is because submit is being used which means that a future is being created and the task is run in the future.

What is excecutionexception in ExecutorService?

Exceptions which are thrown by tasks submitted to ExecutorService#submit get wrapped into an ExcecutionException and are rethrown by the Future.get () method. This is, because the executor considers the exception as part of the result of the task.

Does uncaughtexceptionhandler apply to all threads and tasks in a pool?

The previous UncaughtExceptionHandler approach applies to all threads and tasks in a thread pool. However, if we’re running different tasks in the same thread pool and they require different exception handling logic, this may not be optimal. Or we aren’t even allowed to set a handler because the task submission code is using a preconfigured pool.