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 Summary

Constructors
Constructor
Description
`AbstractExecutorService()`
Constructor for subclasses to call.

## Method Summary

Modifier and Type
Method
Description
`<T> List<Future<T>>`
`invokeAll(Collection<? extends Callable<T>> tasks)`
Executes the given tasks, returning a list of Futures holding their status and results when all complete.
`<T> List<Future<T>>`
`invokeAll(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)`
Executes the given tasks, returning a list of Futures holding their status and results when all complete or the timeout expires, whichever happens first.
`<T> T`
`invokeAny(Collection<? extends Callable<T>> tasks)`
Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do.
`<T> T`
`invokeAny(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)`
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.
`protected <T> RunnableFuture<T>`
`newTaskFor(Runnable runnable, T value)`
Returns a `RunnableFuture` for the given runnable and default value.
`protected <T> RunnableFuture<T>`
`newTaskFor(Callable<T> callable)`
Returns a `RunnableFuture` for the given callable task.
`Future<?>`
`submit(Runnable task)`
Submits a Runnable task for execution and returns a Future representing that task.
`<T> Future<T>`
`submit(Runnable task, T result)`
Submits a Runnable task for execution and returns a Future representing that task.
`<T> Future<T>`
`submit(Callable<T> task)`
Submits a value-returning task for execution and returns a Future representing the pending results of the task.

### Methods declared in class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

### Methods declared in interface java.util.concurrent.Executor

`execute`

### Methods declared in interface java.util.concurrent.ExecutorService

`awaitTermination, isShutdown, isTerminated, shutdown, shutdownNow`

## 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