Module java.base
Package java.util.concurrent

Class AbstractExecutorService

java.lang.Object
java.util.concurrent.AbstractExecutorService
All Implemented Interfaces:
Executor, ExecutorService
Direct Known Subclasses:
ForkJoinPool, ThreadPoolExecutor
public abstract class AbstractExecutorService extends Object implements ExecutorService
Provides default implementations of ExecutorService execution methods. This class implements the submit, invokeAny and invokeAll methods using a RunnableFuture returned by newTaskFor, which defaults to the FutureTask class provided in this package. For example, the implementation of submit(Runnable) creates an associated RunnableFuture that is executed and returned. Subclasses may override the newTaskFor methods to return RunnableFuture implementations other than FutureTask.

Extension example. Here is a sketch of a class that customizes ThreadPoolExecutor to use a CustomTask class instead of the default FutureTask: 

 
 public class CustomThreadPoolExecutor extends ThreadPoolExecutor {

   static class CustomTask<V> implements RunnableFuture<V> {...}

   protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
       return new CustomTask<V>(c);
   }
   protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
       return new CustomTask<V>(r, v);
   }
   // ... add constructors, etc.
 }
Since:
1.5

  • Constructor Details

    • AbstractExecutorService

      public AbstractExecutorService()
      Constructor for subclasses to call.

  • Method Details

    • newTaskFor

      protected <T> RunnableFuture<T> newTaskFor​(Runnable runnable, T value)
      Returns a RunnableFuture for the given runnable and default value.
      Type Parameters:
      T - the type of the given value
      Parameters:
      runnable - the runnable task being wrapped
      value - the default value for the returned future
      Returns:
      a RunnableFuture which, when run, will run the underlying runnable and which, as a Future, will yield the given value as its result and provide for cancellation of the underlying task
      Since:
      1.6

    • newTaskFor

      protected <T> RunnableFuture<T> newTaskFor​(Callable<T> callable)
      Returns a RunnableFuture for the given callable task.
      Type Parameters:
      T - the type of the callable's result
      Parameters:
      callable - the callable task being wrapped
      Returns:
      a RunnableFuture which, when run, will call the underlying callable and which, as a Future, will yield the callable's result as its result and provide for cancellation of the underlying task
      Since:
      1.6

    • submit

      public Future<?> submit​(Runnable task)
      Description copied from interface: ExecutorService
      Submits a Runnable task for execution and returns a Future representing that task. The Future's get method will return null upon successful completion.
      Specified by:
      submit in interface ExecutorService
      Parameters:
      task - the task to submit
      Returns:
      a Future representing pending completion of the task
      Throws:
      RejectedExecutionException - if the task cannot be scheduled for execution
      NullPointerException - if the task is null

    • submit

      public <T> Future<T> submit​(Runnable task, T result)
      Description copied from interface: ExecutorService
      Submits a Runnable task for execution and returns a Future representing that task. The Future's get method will return the given result upon successful completion.
      Specified by:
      submit in interface ExecutorService
      Type Parameters:
      T - the type of the result
      Parameters:
      task - the task to submit
      result - the result to return
      Returns:
      a Future representing pending completion of the task
      Throws:
      RejectedExecutionException - if the task cannot be scheduled for execution
      NullPointerException - if the task is null

    • submit

      public <T> Future<T> submit​(Callable<T> task)
      Description copied from interface: ExecutorService
      Submits a value-returning task for execution and returns a Future representing the pending results of the task. The Future's get method will return the task's result upon successful completion.

      If you would like to immediately block waiting for a task, you can use constructions of the form result = exec.submit(aCallable).get();

      Note: The Executors class includes a set of methods that can convert some other common closure-like objects, for example, PrivilegedAction to Callable form so they can be submitted.

      Specified by:
      submit in interface ExecutorService
      Type Parameters:
      T - the type of the task's result
      Parameters:
      task - the task to submit
      Returns:
      a Future representing pending completion of the task
      Throws:
      RejectedExecutionException - if the task cannot be scheduled for execution
      NullPointerException - if the task is null

    • invokeAny

      public <T> T invokeAny​(Collection<? extends Callable<T>> tasks) throws InterruptedException, ExecutionException
      Description copied from interface: ExecutorService
      Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do. Upon normal or exceptional return, tasks that have not completed are cancelled. The results of this method are undefined if the given collection is modified while this operation is in progress.
      Specified by:
      invokeAny in interface ExecutorService
      Type Parameters:
      T - the type of the values returned from the tasks
      Parameters:
      tasks - the collection of tasks
      Returns:
      the result returned by one of the tasks
      Throws:
      InterruptedException - if interrupted while waiting
      ExecutionException - if no task successfully completes

    • invokeAny

      public <T> T invokeAny​(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException
      Description copied from interface: ExecutorService
      Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do before the given timeout elapses. Upon normal or exceptional return, tasks that have not completed are cancelled. The results of this method are undefined if the given collection is modified while this operation is in progress.
      Specified by:
      invokeAny in interface ExecutorService
      Type Parameters:
      T - the type of the values returned from the tasks
      Parameters:
      tasks - the collection of tasks
      timeout - the maximum time to wait
      unit - the time unit of the timeout argument
      Returns:
      the result returned by one of the tasks
      Throws:
      InterruptedException - if interrupted while waiting
      ExecutionException - if no task successfully completes
      TimeoutException - if the given timeout elapses before any task successfully completes

    • invokeAll

      public <T> List<Future<T>> invokeAll​(Collection<? extends Callable<T>> tasks) throws InterruptedException
      Description copied from interface: ExecutorService
      Executes the given tasks, returning a list of Futures holding their status and results when all complete. Future.isDone() is true for each element of the returned list. Note that a completed task could have terminated either normally or by throwing an exception. The results of this method are undefined if the given collection is modified while this operation is in progress.
      Specified by:
      invokeAll in interface ExecutorService
      Type Parameters:
      T - the type of the values returned from the tasks
      Parameters:
      tasks - the collection of tasks
      Returns:
      a list of Futures representing the tasks, in the same sequential order as produced by the iterator for the given task list, each of which has completed
      Throws:
      InterruptedException - if interrupted while waiting, in which case unfinished tasks are cancelled

    • invokeAll

      public <T> List<Future<T>> invokeAll​(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit) throws InterruptedException
      Description copied from interface: ExecutorService
      Executes the given tasks, returning a list of Futures holding their status and results when all complete or the timeout expires, whichever happens first. Future.isDone() is true for each element of the returned list. Upon return, tasks that have not completed are cancelled. Note that a completed task could have terminated either normally or by throwing an exception. The results of this method are undefined if the given collection is modified while this operation is in progress.
      Specified by:
      invokeAll in interface ExecutorService
      Type Parameters:
      T - the type of the values returned from the tasks
      Parameters:
      tasks - the collection of tasks
      timeout - the maximum time to wait
      unit - the time unit of the timeout argument
      Returns:
      a list of Futures representing the tasks, in the same sequential order as produced by the iterator for the given task list. If the operation did not time out, each task will have completed. If it did time out, some of these tasks will not have completed.
      Throws:
      InterruptedException - if interrupted while waiting, in which case unfinished tasks are cancelled