Package com.google.common.util.concurrent

Class MoreExecutors

  • @GwtCompatible(emulated=true)
public final class MoreExecutors
extends java.lang.Object
    Factory and utility methods for Executor, ExecutorService, and ThreadFactory.
    Since:
    3.0

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      private MoreExecutors()  

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static void addDelayedShutdownHook​(java.util.concurrent.ExecutorService service, long terminationTimeout, java.util.concurrent.TimeUnit timeUnit)
      Add a shutdown hook to wait for thread completion in the given service.
      static void addDelayedShutdownHook​(java.util.concurrent.ExecutorService service, java.time.Duration terminationTimeout)
      Add a shutdown hook to wait for thread completion in the given service.
      static java.util.concurrent.Executor directExecutor()
      Returns an Executor that runs each task in the thread that invokes execute, as in ThreadPoolExecutor.CallerRunsPolicy.
      static java.util.concurrent.ExecutorService getExitingExecutorService​(java.util.concurrent.ThreadPoolExecutor executor)
      Converts the given ThreadPoolExecutor into an ExecutorService that exits when the application is complete.
      static java.util.concurrent.ExecutorService getExitingExecutorService​(java.util.concurrent.ThreadPoolExecutor executor, long terminationTimeout, java.util.concurrent.TimeUnit timeUnit)
      Converts the given ThreadPoolExecutor into an ExecutorService that exits when the application is complete.
      static java.util.concurrent.ExecutorService getExitingExecutorService​(java.util.concurrent.ThreadPoolExecutor executor, java.time.Duration terminationTimeout)
      Converts the given ThreadPoolExecutor into an ExecutorService that exits when the application is complete.
      static java.util.concurrent.ScheduledExecutorService getExitingScheduledExecutorService​(java.util.concurrent.ScheduledThreadPoolExecutor executor)
      Converts the given ScheduledThreadPoolExecutor into a ScheduledExecutorService that exits when the application is complete.
      static java.util.concurrent.ScheduledExecutorService getExitingScheduledExecutorService​(java.util.concurrent.ScheduledThreadPoolExecutor executor, long terminationTimeout, java.util.concurrent.TimeUnit timeUnit)
      Converts the given ScheduledThreadPoolExecutor into a ScheduledExecutorService that exits when the application is complete.
      static java.util.concurrent.ScheduledExecutorService getExitingScheduledExecutorService​(java.util.concurrent.ScheduledThreadPoolExecutor executor, java.time.Duration terminationTimeout)
      Converts the given ScheduledThreadPoolExecutor into a ScheduledExecutorService that exits when the application is complete.
      (package private) static <T> T invokeAnyImpl​(ListeningExecutorService executorService, java.util.Collection<? extends java.util.concurrent.Callable<T>> tasks, boolean timed, long timeout, java.util.concurrent.TimeUnit unit)
      An implementation of ExecutorService.invokeAny(java.util.Collection<? extends java.util.concurrent.Callable<T>>) for ListeningExecutorService implementations.
      (package private) static <T> T invokeAnyImpl​(ListeningExecutorService executorService, java.util.Collection<? extends java.util.concurrent.Callable<T>> tasks, boolean timed, java.time.Duration timeout)
      An implementation of ExecutorService.invokeAny(java.util.Collection<? extends java.util.concurrent.Callable<T>>) for ListeningExecutorService implementations.
      private static boolean isAppEngine()  
      static ListeningExecutorService listeningDecorator​(java.util.concurrent.ExecutorService delegate)
      Creates an ExecutorService whose submit and invokeAll methods submit ListenableFutureTask instances to the given delegate executor.
      static ListeningScheduledExecutorService listeningDecorator​(java.util.concurrent.ScheduledExecutorService delegate)
      Creates a ScheduledExecutorService whose submit and invokeAll methods submit ListenableFutureTask instances to the given delegate executor.
      static ListeningExecutorService newDirectExecutorService()
      Creates an executor service that runs each task in the thread that invokes execute/submit, as in ThreadPoolExecutor.CallerRunsPolicy This applies both to individually submitted tasks and to collections of tasks submitted via invokeAll or invokeAny.
      static java.util.concurrent.Executor newSequentialExecutor​(java.util.concurrent.Executor delegate)
      Returns an Executor that runs each task executed sequentially, such that no two tasks are running concurrently.
      (package private) static java.lang.Thread newThread​(java.lang.String name, java.lang.Runnable runnable)
      Creates a thread using platformThreadFactory(), and sets its name to name unless changing the name is forbidden by the security manager.
      static java.util.concurrent.ThreadFactory platformThreadFactory()
      Returns a default thread factory used to create new threads.
      (package private) static java.util.concurrent.Executor rejectionPropagatingExecutor​(java.util.concurrent.Executor delegate, AbstractFuture<?> future)
      Returns an Executor that will propagate RejectedExecutionException from the delegate executor to the given future.
      (package private) static java.util.concurrent.Executor renamingDecorator​(java.util.concurrent.Executor executor, Supplier<java.lang.String> nameSupplier)
      Creates an Executor that renames the threads that its tasks run in.
      (package private) static java.util.concurrent.ExecutorService renamingDecorator​(java.util.concurrent.ExecutorService service, Supplier<java.lang.String> nameSupplier)
      Creates an ExecutorService that renames the threads that its tasks run in.
      (package private) static java.util.concurrent.ScheduledExecutorService renamingDecorator​(java.util.concurrent.ScheduledExecutorService service, Supplier<java.lang.String> nameSupplier)
      Creates a ScheduledExecutorService that renames the threads that its tasks run in.
      static boolean shutdownAndAwaitTermination​(java.util.concurrent.ExecutorService service, long timeout, java.util.concurrent.TimeUnit unit)
      Shuts down the given executor service gradually, first disabling new submissions and later, if necessary, cancelling remaining tasks.
      static boolean shutdownAndAwaitTermination​(java.util.concurrent.ExecutorService service, java.time.Duration timeout)
      Shuts down the given executor service gradually, first disabling new submissions and later, if necessary, cancelling remaining tasks.
      private static <T> ListenableFuture<T> submitAndAddQueueListener​(ListeningExecutorService executorService, java.util.concurrent.Callable<T> task, java.util.concurrent.BlockingQueue<java.util.concurrent.Future<T>> queue)
      Submits the task and adds a listener that adds the future to queue when it completes.
      private static void useDaemonThreadFactory​(java.util.concurrent.ThreadPoolExecutor executor)  

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • MoreExecutors

        private MoreExecutors()

    • Method Detail

      • getExitingExecutorService

        @Beta
@GwtIncompatible
public static java.util.concurrent.ExecutorService getExitingExecutorService​(java.util.concurrent.ThreadPoolExecutor executor,
                                                                             java.time.Duration terminationTimeout)
        Converts the given ThreadPoolExecutor into an ExecutorService that exits when the application is complete. It does so by using daemon threads and adding a shutdown hook to wait for their completion.

        This is mainly for fixed thread pools. See Executors.newFixedThreadPool(int).

        Parameters:
        executor - the executor to modify to make sure it exits when the application is finished
        terminationTimeout - how long to wait for the executor to finish before terminating the JVM
        Returns:
        an unmodifiable version of the input which will not hang the JVM
        Since:
        28.0

      • getExitingExecutorService

        @Beta
@GwtIncompatible
public static java.util.concurrent.ExecutorService getExitingExecutorService​(java.util.concurrent.ThreadPoolExecutor executor,
                                                                             long terminationTimeout,
                                                                             java.util.concurrent.TimeUnit timeUnit)
        Converts the given ThreadPoolExecutor into an ExecutorService that exits when the application is complete. It does so by using daemon threads and adding a shutdown hook to wait for their completion.

        This is mainly for fixed thread pools. See Executors.newFixedThreadPool(int).

        Parameters:
        executor - the executor to modify to make sure it exits when the application is finished
        terminationTimeout - how long to wait for the executor to finish before terminating the JVM
        timeUnit - unit of time for the time parameter
        Returns:
        an unmodifiable version of the input which will not hang the JVM

      • getExitingExecutorService

        @Beta
@GwtIncompatible
public static java.util.concurrent.ExecutorService getExitingExecutorService​(java.util.concurrent.ThreadPoolExecutor executor)
        Converts the given ThreadPoolExecutor into an ExecutorService that exits when the application is complete. It does so by using daemon threads and adding a shutdown hook to wait for their completion.

        This method waits 120 seconds before continuing with JVM termination, even if the executor has not finished its work.

        This is mainly for fixed thread pools. See Executors.newFixedThreadPool(int).

        Parameters:
        executor - the executor to modify to make sure it exits when the application is finished
        Returns:
        an unmodifiable version of the input which will not hang the JVM

      • getExitingScheduledExecutorService

        @Beta
@GwtIncompatible
public static java.util.concurrent.ScheduledExecutorService getExitingScheduledExecutorService​(java.util.concurrent.ScheduledThreadPoolExecutor executor,
                                                                                               java.time.Duration terminationTimeout)
        Converts the given ScheduledThreadPoolExecutor into a ScheduledExecutorService that exits when the application is complete. It does so by using daemon threads and adding a shutdown hook to wait for their completion.

        This is mainly for fixed thread pools. See Executors.newScheduledThreadPool(int).

        Parameters:
        executor - the executor to modify to make sure it exits when the application is finished
        terminationTimeout - how long to wait for the executor to finish before terminating the JVM
        Returns:
        an unmodifiable version of the input which will not hang the JVM
        Since:
        28.0

      • getExitingScheduledExecutorService

        @Beta
@GwtIncompatible
public static java.util.concurrent.ScheduledExecutorService getExitingScheduledExecutorService​(java.util.concurrent.ScheduledThreadPoolExecutor executor,
                                                                                               long terminationTimeout,
                                                                                               java.util.concurrent.TimeUnit timeUnit)
        Converts the given ScheduledThreadPoolExecutor into a ScheduledExecutorService that exits when the application is complete. It does so by using daemon threads and adding a shutdown hook to wait for their completion.

        This is mainly for fixed thread pools. See Executors.newScheduledThreadPool(int).

        Parameters:
        executor - the executor to modify to make sure it exits when the application is finished
        terminationTimeout - how long to wait for the executor to finish before terminating the JVM
        timeUnit - unit of time for the time parameter
        Returns:
        an unmodifiable version of the input which will not hang the JVM

      • getExitingScheduledExecutorService

        @Beta
@GwtIncompatible
public static java.util.concurrent.ScheduledExecutorService getExitingScheduledExecutorService​(java.util.concurrent.ScheduledThreadPoolExecutor executor)
        Converts the given ScheduledThreadPoolExecutor into a ScheduledExecutorService that exits when the application is complete. It does so by using daemon threads and adding a shutdown hook to wait for their completion.

        This method waits 120 seconds before continuing with JVM termination, even if the executor has not finished its work.

        This is mainly for fixed thread pools. See Executors.newScheduledThreadPool(int).

        Parameters:
        executor - the executor to modify to make sure it exits when the application is finished
        Returns:
        an unmodifiable version of the input which will not hang the JVM

      • addDelayedShutdownHook

        @Beta
@GwtIncompatible
public static void addDelayedShutdownHook​(java.util.concurrent.ExecutorService service,
                                          java.time.Duration terminationTimeout)
        Add a shutdown hook to wait for thread completion in the given service. This is useful if the given service uses daemon threads, and we want to keep the JVM from exiting immediately on shutdown, instead giving these daemon threads a chance to terminate normally.
        Parameters:
        service - ExecutorService which uses daemon threads
        terminationTimeout - how long to wait for the executor to finish before terminating the JVM
        Since:
        28.0

      • addDelayedShutdownHook

        @Beta
@GwtIncompatible
public static void addDelayedShutdownHook​(java.util.concurrent.ExecutorService service,
                                          long terminationTimeout,
                                          java.util.concurrent.TimeUnit timeUnit)
        Add a shutdown hook to wait for thread completion in the given service. This is useful if the given service uses daemon threads, and we want to keep the JVM from exiting immediately on shutdown, instead giving these daemon threads a chance to terminate normally.
        Parameters:
        service - ExecutorService which uses daemon threads
        terminationTimeout - how long to wait for the executor to finish before terminating the JVM
        timeUnit - unit of time for the time parameter

      • useDaemonThreadFactory

        @GwtIncompatible
private static void useDaemonThreadFactory​(java.util.concurrent.ThreadPoolExecutor executor)

      • newDirectExecutorService

        @GwtIncompatible
public static ListeningExecutorService newDirectExecutorService()
        Creates an executor service that runs each task in the thread that invokes execute/submit, as in ThreadPoolExecutor.CallerRunsPolicy This applies both to individually submitted tasks and to collections of tasks submitted via invokeAll or invokeAny. In the latter case, tasks will run serially on the calling thread. Tasks are run to completion before a Future is returned to the caller (unless the executor has been shutdown).

        Although all tasks are immediately executed in the thread that submitted the task, this ExecutorService imposes a small locking overhead on each task submission in order to implement shutdown and termination behavior.

        The implementation deviates from the ExecutorService specification with regards to the shutdownNow method. First, "best-effort" with regards to canceling running tasks is implemented as "no-effort". No interrupts or other attempts are made to stop threads executing tasks. Second, the returned list will always be empty, as any submitted task is considered to have started execution. This applies also to tasks given to invokeAll or invokeAny which are pending serial execution, even the subset of the tasks that have not yet started execution. It is unclear from the ExecutorService specification if these should be included, and it's much easier to implement the interpretation that they not be. Finally, a call to shutdown or shutdownNow may result in concurrent calls to invokeAll/invokeAny throwing RejectedExecutionException, although a subset of the tasks may already have been executed.

        Since:
        18.0 (present as MoreExecutors.sameThreadExecutor() since 10.0)

      • directExecutor

        public static java.util.concurrent.Executor directExecutor()
        Returns an Executor that runs each task in the thread that invokes execute, as in ThreadPoolExecutor.CallerRunsPolicy.

        This instance is equivalent to: 

        
 final class DirectExecutor implements Executor {
   public void execute(Runnable r) {
     r.run();
   }
 }

        This should be preferred to newDirectExecutorService() because implementing the ExecutorService subinterface necessitates significant performance overhead.

        Since:
        18.0

      • newSequentialExecutor

        @Beta
@GwtIncompatible
public static java.util.concurrent.Executor newSequentialExecutor​(java.util.concurrent.Executor delegate)
        Returns an Executor that runs each task executed sequentially, such that no two tasks are running concurrently. Submitted tasks have a happens-before order as defined in the Java Language Specification.

        The executor uses delegate in order to execute each task in turn, and does not create any threads of its own.

        After execution begins on a thread from the delegate Executor, tasks are polled and executed from a task queue until there are no more tasks. The thread will not be released until there are no more tasks to run.

        If a task is submitted while a thread is executing tasks from the task queue, the thread will not be released until that submitted task is also complete.

        If a task is interrupted while a task is running:

        1. execution will not stop until the task queue is empty.
        2. tasks will begin execution with the thread marked as not interrupted - any interruption applies only to the task that was running at the point of interruption.
        3. if the thread was interrupted before the SequentialExecutor's worker begins execution, the interrupt will be restored to the thread after it completes so that its delegate Executor may process the interrupt.
        4. subtasks are run with the thread uninterrupted and interrupts received during execution of a task are ignored.

        RuntimeExceptions thrown by tasks are simply logged and the executor keeps trucking. If an Error is thrown, the error will propagate and execution will stop until the next time a task is submitted.

        When an Error is thrown by an executed task, previously submitted tasks may never run. An attempt will be made to restart execution on the next call to execute. If the delegate has begun to reject execution, the previously submitted tasks may never run, despite not throwing a RejectedExecutionException synchronously with the call to execute. If this behaviour is problematic, use an Executor with a single thread (e.g. Executors.newSingleThreadExecutor()).

        Since:
        23.3 (since 23.1 as sequentialExecutor)

      • listeningDecorator

        @GwtIncompatible
public static ListeningExecutorService listeningDecorator​(java.util.concurrent.ExecutorService delegate)
        Creates an ExecutorService whose submit and invokeAll methods submit ListenableFutureTask instances to the given delegate executor. Those methods, as well as execute and invokeAny, are implemented in terms of calls to delegate.execute. All other methods are forwarded unchanged to the delegate. This implies that the returned ListeningExecutorService never calls the delegate's submit, invokeAll, and invokeAny methods, so any special handling of tasks must be implemented in the delegate's execute method or by wrapping the returned ListeningExecutorService.

        If the delegate executor was already an instance of ListeningExecutorService, it is returned untouched, and the rest of this documentation does not apply.

        Since:
        10.0

      • listeningDecorator

        @GwtIncompatible
public static ListeningScheduledExecutorService listeningDecorator​(java.util.concurrent.ScheduledExecutorService delegate)
        Creates a ScheduledExecutorService whose submit and invokeAll methods submit ListenableFutureTask instances to the given delegate executor. Those methods, as well as execute and invokeAny, are implemented in terms of calls to delegate.execute. All other methods are forwarded unchanged to the delegate. This implies that the returned ListeningScheduledExecutorService never calls the delegate's submit, invokeAll, and invokeAny methods, so any special handling of tasks must be implemented in the delegate's execute method or by wrapping the returned ListeningScheduledExecutorService.

        If the delegate executor was already an instance of ListeningScheduledExecutorService, it is returned untouched, and the rest of this documentation does not apply.

        Since:
        10.0

      • invokeAnyImpl

        @GwtIncompatible
static <T> T invokeAnyImpl​(ListeningExecutorService executorService,
                           java.util.Collection<? extends java.util.concurrent.Callable<T>> tasks,
                           boolean timed,
                           java.time.Duration timeout)
                    throws java.lang.InterruptedException,
                           java.util.concurrent.ExecutionException,
                           java.util.concurrent.TimeoutException
        An implementation of ExecutorService.invokeAny(java.util.Collection<? extends java.util.concurrent.Callable<T>>) for ListeningExecutorService implementations.
        Throws:
        java.lang.InterruptedException
        java.util.concurrent.ExecutionException
        java.util.concurrent.TimeoutException

      • invokeAnyImpl

        @GwtIncompatible
static <T> T invokeAnyImpl​(ListeningExecutorService executorService,
                           java.util.Collection<? extends java.util.concurrent.Callable<T>> tasks,
                           boolean timed,
                           long timeout,
                           java.util.concurrent.TimeUnit unit)
                    throws java.lang.InterruptedException,
                           java.util.concurrent.ExecutionException,
                           java.util.concurrent.TimeoutException
        An implementation of ExecutorService.invokeAny(java.util.Collection<? extends java.util.concurrent.Callable<T>>) for ListeningExecutorService implementations.
        Throws:
        java.lang.InterruptedException
        java.util.concurrent.ExecutionException
        java.util.concurrent.TimeoutException

      • submitAndAddQueueListener

        @GwtIncompatible
private static <T> ListenableFuture<T> submitAndAddQueueListener​(ListeningExecutorService executorService,
                                                                 java.util.concurrent.Callable<T> task,
                                                                 java.util.concurrent.BlockingQueue<java.util.concurrent.Future<T>> queue)
        Submits the task and adds a listener that adds the future to queue when it completes.

      • platformThreadFactory

        @Beta
@GwtIncompatible
public static java.util.concurrent.ThreadFactory platformThreadFactory()
        Returns a default thread factory used to create new threads.

        On AppEngine, returns ThreadManager.currentRequestThreadFactory(). Otherwise, returns Executors.defaultThreadFactory().

        Since:
        14.0

      • newThread

        @GwtIncompatible
static java.lang.Thread newThread​(java.lang.String name,
                                  java.lang.Runnable runnable)
        Creates a thread using platformThreadFactory(), and sets its name to name unless changing the name is forbidden by the security manager.

      • renamingDecorator

        @GwtIncompatible
static java.util.concurrent.Executor renamingDecorator​(java.util.concurrent.Executor executor,
                                                       Supplier<java.lang.String> nameSupplier)
        Creates an Executor that renames the threads that its tasks run in.

        The names are retrieved from the nameSupplier on the thread that is being renamed right before each task is run. The renaming is best effort, if a SecurityManager prevents the renaming then it will be skipped but the tasks will still execute.

        Parameters:
        executor - The executor to decorate
        nameSupplier - The source of names for each task

      • renamingDecorator

        @GwtIncompatible
static java.util.concurrent.ExecutorService renamingDecorator​(java.util.concurrent.ExecutorService service,
                                                              Supplier<java.lang.String> nameSupplier)
        Creates an ExecutorService that renames the threads that its tasks run in.

        The names are retrieved from the nameSupplier on the thread that is being renamed right before each task is run. The renaming is best effort, if a SecurityManager prevents the renaming then it will be skipped but the tasks will still execute.

        Parameters:
        service - The executor to decorate
        nameSupplier - The source of names for each task

      • renamingDecorator

        @GwtIncompatible
static java.util.concurrent.ScheduledExecutorService renamingDecorator​(java.util.concurrent.ScheduledExecutorService service,
                                                                       Supplier<java.lang.String> nameSupplier)
        Creates a ScheduledExecutorService that renames the threads that its tasks run in.

        The names are retrieved from the nameSupplier on the thread that is being renamed right before each task is run. The renaming is best effort, if a SecurityManager prevents the renaming then it will be skipped but the tasks will still execute.

        Parameters:
        service - The executor to decorate
        nameSupplier - The source of names for each task

      • shutdownAndAwaitTermination

        @Beta
@GwtIncompatible
public static boolean shutdownAndAwaitTermination​(java.util.concurrent.ExecutorService service,
                                                  java.time.Duration timeout)
        Shuts down the given executor service gradually, first disabling new submissions and later, if necessary, cancelling remaining tasks.

        The method takes the following steps:

        1. calls ExecutorService.shutdown(), disabling acceptance of new submitted tasks.
        2. awaits executor service termination for half of the specified timeout.
        3. if the timeout expires, it calls ExecutorService.shutdownNow(), cancelling pending tasks and interrupting running tasks.
        4. awaits executor service termination for the other half of the specified timeout.

        If, at any step of the process, the calling thread is interrupted, the method calls ExecutorService.shutdownNow() and returns.

        Parameters:
        service - the ExecutorService to shut down
        timeout - the maximum time to wait for the ExecutorService to terminate
        Returns:
        true if the ExecutorService was terminated successfully, false if the call timed out or was interrupted
        Since:
        28.0

      • shutdownAndAwaitTermination

        @Beta
@GwtIncompatible
public static boolean shutdownAndAwaitTermination​(java.util.concurrent.ExecutorService service,
                                                  long timeout,
                                                  java.util.concurrent.TimeUnit unit)
        Shuts down the given executor service gradually, first disabling new submissions and later, if necessary, cancelling remaining tasks.

        The method takes the following steps:

        1. calls ExecutorService.shutdown(), disabling acceptance of new submitted tasks.
        2. awaits executor service termination for half of the specified timeout.
        3. if the timeout expires, it calls ExecutorService.shutdownNow(), cancelling pending tasks and interrupting running tasks.
        4. awaits executor service termination for the other half of the specified timeout.

        If, at any step of the process, the calling thread is interrupted, the method calls ExecutorService.shutdownNow() and returns.

        Parameters:
        service - the ExecutorService to shut down
        timeout - the maximum time to wait for the ExecutorService to terminate
        unit - the time unit of the timeout argument
        Returns:
        true if the ExecutorService was terminated successfully, false if the call timed out or was interrupted
        Since:
        17.0

      • rejectionPropagatingExecutor

        static java.util.concurrent.Executor rejectionPropagatingExecutor​(java.util.concurrent.Executor delegate,
                                                                  AbstractFuture<?> future)
        Returns an Executor that will propagate RejectedExecutionException from the delegate executor to the given future.

        Note, the returned executor can only be used once.