MoreExecutors (Guava: Google Core Libraries for Java 20.0 API)

java.lang.Object
- com.google.common.util.concurrent.MoreExecutors

```
@GwtCompatible(emulated=true)
public final class MoreExecutors
extends Object
```
Factory and utility methods for Executor, ExecutorService, and ThreadFactory.

Since:

3.0

Author:

Eric Fellheimer, Kyle Littlefield, Justin Mahoney

Method Summary

All Methods Static Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`static void`	`addDelayedShutdownHook(ExecutorService service, long terminationTimeout, TimeUnit timeUnit)` Add a shutdown hook to wait for thread completion in the given `service`.
`static Executor`	`directExecutor()` Returns an `Executor` that runs each task in the thread that invokes `execute`, as in `ThreadPoolExecutor.CallerRunsPolicy`.
`static ExecutorService`	`getExitingExecutorService(ThreadPoolExecutor executor)` Converts the given ThreadPoolExecutor into an ExecutorService that exits when the application is complete.
`static ExecutorService`	`getExitingExecutorService(ThreadPoolExecutor executor, long terminationTimeout, TimeUnit timeUnit)` Converts the given ThreadPoolExecutor into an ExecutorService that exits when the application is complete.
`static ScheduledExecutorService`	`getExitingScheduledExecutorService(ScheduledThreadPoolExecutor executor)` Converts the given ScheduledThreadPoolExecutor into a ScheduledExecutorService that exits when the application is complete.
`static ScheduledExecutorService`	`getExitingScheduledExecutorService(ScheduledThreadPoolExecutor executor, long terminationTimeout, TimeUnit timeUnit)` Converts the given ScheduledThreadPoolExecutor into a ScheduledExecutorService that exits when the application is complete.
`static ListeningExecutorService`	`listeningDecorator(ExecutorService delegate)` Creates an `ExecutorService` whose `submit` and `invokeAll` methods submit `ListenableFutureTask` instances to the given delegate executor.
`static ListeningScheduledExecutorService`	`listeningDecorator(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 ThreadFactory`	`platformThreadFactory()` Returns a default thread factory used to create new threads.
`static ListeningExecutorService`	`sameThreadExecutor()` Deprecated. Use `directExecutor()` if you only require an `Executor` and `newDirectExecutorService()` if you need a `ListeningExecutorService`. This method will be removed in Guava 21.0.
`static boolean`	`shutdownAndAwaitTermination(ExecutorService service, long timeout, TimeUnit unit)` Shuts down the given executor service gradually, first disabling new submissions and later, if necessary, cancelling remaining tasks.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Method Detail
  - getExitingExecutorService
```
@Beta
 @GwtIncompatible
public static ExecutorService getExitingExecutorService(ThreadPoolExecutor executor,
                                                                                long terminationTimeout,
                                                                                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
  - getExitingScheduledExecutorService
```
@Beta
 @GwtIncompatible
public static ScheduledExecutorService getExitingScheduledExecutorService(ScheduledThreadPoolExecutor executor,
                                                                                                  long terminationTimeout,
                                                                                                  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
  - addDelayedShutdownHook
```
@Beta
 @GwtIncompatible
public static void addDelayedShutdownHook(ExecutorService service,
                                                                  long terminationTimeout,
                                                                  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
  - getExitingExecutorService
```
@Beta
 @GwtIncompatible
public static ExecutorService getExitingExecutorService(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 ScheduledExecutorService getExitingScheduledExecutorService(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
  - sameThreadExecutor
```
@Deprecated
 @GwtIncompatible
public static ListeningExecutorService sameThreadExecutor()
```
    Deprecated. Use directExecutor() if you only require an Executor and newDirectExecutorService() if you need a ListeningExecutorService. This method will be removed in Guava 21.0.
    
    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:
    
    10.0 (mostly source-compatible since 3.0)
  - 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 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
  - listeningDecorator
```
@GwtIncompatible
public static ListeningExecutorService listeningDecorator(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(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
  - platformThreadFactory
```
@Beta
 @GwtIncompatible
public static ThreadFactory platformThreadFactory()
```
    Returns a default thread factory used to create new threads.
    On AppEngine, returns ThreadManager.currentRequestThreadFactory(). Otherwise, returns Executors.defaultThreadFactory().
    
    Since:
    
    14.0
  - shutdownAndAwaitTermination
```
@Beta
 @GwtIncompatible
public static boolean shutdownAndAwaitTermination(ExecutorService service,
                                                                          long timeout,
                                                                          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

Class MoreExecutors

Method Summary

Methods inherited from class java.lang.Object

Method Detail

getExitingExecutorService

getExitingScheduledExecutorService

addDelayedShutdownHook

getExitingExecutorService

getExitingScheduledExecutorService

sameThreadExecutor

newDirectExecutorService

directExecutor

listeningDecorator

listeningDecorator

platformThreadFactory

shutdownAndAwaitTermination