| java.util.concurrent.ExecutorService
All known Subclasses: java.util.concurrent.AbstractExecutorService,
| ExecutorService | | public interface ExecutorService extends Executor(Code) | | An
Executor that provides methods to manage termination and
methods that can produce a
Future for tracking progress of
one or more asynchronous tasks.
An ExecutorService can be shut down, which will cause it
to stop accepting new tasks. After being shut down, the executor
will eventually terminate, at which point no tasks are actively
executing, no tasks are awaiting execution, and no new tasks can be
submitted.
Method submit extends base method
Executor.execute by creating and returning a
Future that
can be used to cancel execution and/or wait for completion.
Methods invokeAny and invokeAll perform the most
commonly useful forms of bulk execution, executing a collection of
tasks and then waiting for at least one, or all, to
complete. (Class
ExecutorCompletionService can be used to
write customized variants of these methods.)
The
Executors class provides factory methods for the
executor services provided in this package.
Usage Example
Here is a sketch of a network service in which threads in a thread
pool service incoming requests. It uses the preconfigured
Executors.newFixedThreadPool factory method:
class NetworkService {
private final ServerSocket serverSocket;
private final ExecutorService pool;
public NetworkService(int port, int poolSize) throws IOException {
serverSocket = new ServerSocket(port);
pool = Executors.newFixedThreadPool(poolSize);
}
public void serve() {
try {
for (;;) {
pool.execute(new Handler(serverSocket.accept()));
}
} catch (IOException ex) {
pool.shutdown();
}
}
}
class Handler implements Runnable {
private final Socket socket;
Handler(Socket socket) { this.socket = socket; }
public void run() {
// read and service request
}
}
since:
1.5
author:
Doug Lea |
| Method Summary | |
| boolean | awaitTermination(long timeout, TimeUnit unit)
Blocks until all tasks have completed execution after a shutdown
request, or the timeout occurs, or the current thread is
interrupted, whichever happens first. | | List<Future<T>> | invokeAll(Collection<Callable<T>> tasks)
Executes the given tasks, returning their results
when all complete. | | List<Future<T>> | invokeAll(Collection<Callable<T>> tasks, long timeout, TimeUnit unit)
Executes the given tasks, returning their results
when all complete or the timeout expires, whichever happens first.
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.
Parameters:
tasks - the collection of tasks
Parameters:
timeout - the maximum time to wait
Parameters:
unit - the time unit of the timeout argument A list of Futures representing the tasks, in the samesequential order as produced by the iterator for the giventask list. | | T | invokeAny(Collection<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 | invokeAny(Collection<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. | | boolean | isShutdown()
Returns true if this executor has been shut down. | | boolean | isTerminated()
Returns true if all tasks have completed following shut down. | | void | shutdown()
Initiates an orderly shutdown in which previously submitted
tasks are executed, but no new tasks will be
accepted. | | List<Runnable> | shutdownNow()
Attempts to stop all actively executing tasks, halts the
processing of waiting tasks, and returns a list of the tasks that were
awaiting execution. | | Future<T> | submit(Callable<T> task)
Submits a value-returning task for execution and returns a Future
representing the pending results of the task. | | Future<T> | submit(Runnable task, T result)
| | Future | submit(Runnable task)
Submits a Runnable task for execution and returns a Future
representing that task. |
| awaitTermination | | boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException(Code) | | Blocks until all tasks have completed execution after a shutdown
request, or the timeout occurs, or the current thread is
interrupted, whichever happens first.
Parameters:
timeout - the maximum time to wait
Parameters:
unit - the time unit of the timeout argument true if this executor terminated and falseif the timeout elapsed before termination
throws:
InterruptedException - if interrupted while waiting |
| invokeAll | | List<Future<T>> invokeAll(Collection<Callable<T>> tasks) throws InterruptedException(Code) | | Executes the given tasks, returning their results
when all complete.
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.
Parameters:
tasks - the collection of tasks A list of Futures representing the tasks, in the samesequential order as produced by the iterator for the given tasklist, each of which has completed.
throws:
InterruptedException - if interrupted while waiting, inwhich case unfinished tasks are cancelled.
throws:
NullPointerException - if tasks or any of its elements are null
throws:
RejectedExecutionException - if any task cannot be scheduledfor execution |
| invokeAll | | List<Future<T>> invokeAll(Collection<Callable<T>> tasks, long timeout, TimeUnit unit) throws InterruptedException(Code) | | Executes the given tasks, returning their results
when all complete or the timeout expires, whichever happens first.
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.
Parameters:
tasks - the collection of tasks
Parameters:
timeout - the maximum time to wait
Parameters:
unit - the time unit of the timeout argument A list of Futures representing the tasks, in the samesequential order as produced by the iterator for the giventask list. If the operation did not time out, each task willhave completed. If it did time out, some of thiese tasks willnot have completed.
throws:
InterruptedException - if interrupted while waiting, inwhich case unfinished tasks are cancelled.
throws:
NullPointerException - if tasks, any of its elements, orunit are null
throws:
RejectedExecutionException - if any task cannot be scheduledfor execution |
| invokeAny | | T invokeAny(Collection<Callable<T>> tasks, long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException(Code) | | 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.
Parameters:
tasks - the collection of tasks
Parameters:
timeout - the maximum time to wait
Parameters:
unit - the time unit of the timeout argument The result returned by one of the tasks.
throws:
InterruptedException - if interrupted while waiting
throws:
NullPointerException - if tasks, any of its elements, orunit are null
throws:
TimeoutException - if the given timeout elapses beforeany task successfully completes
throws:
ExecutionException - if no task successfully completes
throws:
RejectedExecutionException - if tasks cannot be scheduledfor execution |
| isShutdown | | boolean isShutdown()(Code) | | Returns true if this executor has been shut down.
true if this executor has been shut down |
| isTerminated | | boolean isTerminated()(Code) | | Returns true if all tasks have completed following shut down.
Note that isTerminated is never true unless
either shutdown or shutdownNow was called first.
true if all tasks have completed following shut down |
| shutdown | | void shutdown()(Code) | | Initiates an orderly shutdown in which previously submitted
tasks are executed, but no new tasks will be
accepted. Invocation has no additional effect if already shut
down.
throws:
SecurityException - if a security manager exists andshutting down this ExecutorService may manipulate threads thatthe caller is not permitted to modify because it does not holdjava.lang.RuntimePermission("modifyThread"),or the security manager's checkAccess method denies access. |
| shutdownNow | | List<Runnable> shutdownNow()(Code) | | Attempts to stop all actively executing tasks, halts the
processing of waiting tasks, and returns a list of the tasks that were
awaiting execution.
There are no guarantees beyond best-effort attempts to stop
processing actively executing tasks. For example, typical
implementations will cancel via
Thread.interrupt , so if any
tasks mask or fail to respond to interrupts, they may never terminate.
list of tasks that never commenced execution
throws:
SecurityException - if a security manager exists andshutting down this ExecutorService may manipulate threads thatthe caller is not permitted to modify because it does not holdjava.lang.RuntimePermission("modifyThread"),or the security manager's checkAccess method denies access. |
| submit | | Future<T> submit(Callable<T> task)(Code) | | Submits a value-returning task for execution and returns a Future
representing the pending results of the task.
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,
java.security.PrivilegedAction to
Callable form so they can be submitted.
Parameters:
task - the task to submit a Future representing pending completion of the task
throws:
RejectedExecutionException - if task cannot be scheduledfor execution
throws:
NullPointerException - if task null |
| submit | | Future<T> submit(Runnable task, T result)(Code) | | Submits a Runnable task for execution and returns a Future
representing that task that will upon completion return
the given result
Parameters:
task - the task to submit
Parameters:
result - the result to return a Future representing pending completion of the task,and whose get() method will return the given resultupon completion.
throws:
RejectedExecutionException - if task cannot be scheduledfor execution
throws:
NullPointerException - if task null |
| submit | | Future submit(Runnable task)(Code) | | Submits a Runnable task for execution and returns a Future
representing that task.
Parameters:
task - the task to submit a Future representing pending completion of the task,and whose get() method will return nullupon completion.
throws:
RejectedExecutionException - if task cannot be scheduledfor execution
throws:
NullPointerException - if task null |
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