How to start programming

Category: Concurrency

  • How to Cancel a Task in Java ExecutorService

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    Learn to cancel a task submitted to an executor service if the task still has to be executed and/or has not been completed yet. We can use the cancel() method of Future object that allows making the cancellation requests. 1. Future cancel() API The Future.cancel() method takes one argument of type boolean. boolean cancel(boolean mayInterruptIfRunning); Depending on the value of mayInterruptIfRunning and the status of the task submitted…

  • Java – Waiting for Running Threads to Finish

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    Java concurrency allows running multiple sub-tasks of a task in separate threads. Sometimes, it is necessary to wait until all the threads have finished their execution. In this tutorial, we will learn a few ways to make the current thread wait for the other threads to finish. 1. Using ExecutorService and Future.get() Java ExecutorService (or ThreadPoolExecutor) helps execute Runnable or Callable tasks asynchronously. Its submit() method returns a Future object…

  • ExecutorService invokeAny()

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    Learn to use ExecutorService.invokeAny(tasks) method where we execute multiple tasks at the same time, but we make a decision when any one of those tasks is completed and return its result. 1. invokeAny() method This method executes the given list of tasks, returning the result of one that has completed successfully (i.e., without throwing an exception),…

  • Java ExecutorService invokeAll()

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    Learn to run multiple Callable tasks with ExecutorService.invokeAll() API and processing all the results returned from tasks in form of Future class instances in this ExecutorService Callable example. 1. ExecutorService invokeAll() API The invokeAll() method executes the given list of Callable tasks, returning a list of Future objects holding their status and results when all are complete. It is an overloaded method and is in two forms. The second method takes extra…

  • How to Shutdown a Java ExecutorService

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    ExecutorService interface provides 3 methods shutdown(), shutdownNow() and awaitTermination​() for controlling the termination of tasks submitted to executors. Learn how to use these methods under different requirements. 1. Difference between shutdown(), shutdownNow() and awaitTermination​() Let us start with checking out the syntax of these methods. void shutdown(); List<Runnable> shutdownNow(); boolean awaitTermination(long timeout, TimeUnit unit); he shutdown() initiates an orderly shutdown in which previously…