Futures (Guava: Google Core Libraries for Java 23.6.1-jre API)

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

```
@Beta
 @GwtCompatible(emulated=true)
public final class Futures
extends Object
```
Static utility methods pertaining to the Future interface.
Many of these methods use the ListenableFuture API; consult the Guava User Guide article on ListenableFuture.
The main purpose of ListenableFuture is to help you chain together a graph of asynchronous operations. You can chain them together manually with calls to methods like Futures.transform, but you will often find it easier to use a framework. Frameworks automate the process, often adding features like monitoring, debugging, and cancellation. Examples of frameworks include:
- Dagger Producers
If you do chain your operations manually, you may want to use FluentFuture.
Since:

1.0

Author:

Kevin Bourrillion, Nishant Thakkar, Sven Mawson

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static class`	`Futures.FutureCombiner<V>` A helper to create a new `ListenableFuture` whose result is generated from a combination of input futures.

Method Summary

All Methods Static Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`static <V> void`	`addCallback(ListenableFuture<V> future, FutureCallback<? super V> callback)` Deprecated. Use the overload that requires an executor. For identical behavior, pass `MoreExecutors.directExecutor()`, but consider whether another executor would be safer, as discussed in the `ListenableFuture.addListener` documentation. This method is scheduled to be removed in April 2018.
`static <V> void`	`addCallback(ListenableFuture<V> future, FutureCallback<? super V> callback, Executor executor)` Registers separate success and failure callbacks to be run when the `Future`'s computation is complete or, if the computation is already complete, immediately.
`static <V> ListenableFuture<List<V>>`	`allAsList(Iterable<? extends ListenableFuture<? extends V>> futures)` Creates a new `ListenableFuture` whose value is a list containing the values of all its input futures, if all succeed.
`static <V> ListenableFuture<List<V>>`	`allAsList(ListenableFuture<? extends V>... futures)` Creates a new `ListenableFuture` whose value is a list containing the values of all its input futures, if all succeed.
`static <V,X extends Throwable> ListenableFuture<V>`	`catching(ListenableFuture<? extends V> input, Class<X> exceptionType, Function<? super X,? extends V> fallback)` Deprecated. Use the overload that requires an executor. For identical behavior, pass `MoreExecutors.directExecutor()`, but consider whether another executor would be safer, as discussed in the `ListenableFuture.addListener` documentation. This method is scheduled to be removed in April 2018.
`static <V,X extends Throwable> ListenableFuture<V>`	`catching(ListenableFuture<? extends V> input, Class<X> exceptionType, Function<? super X,? extends V> fallback, Executor executor)` Returns a `Future` whose result is taken from the given primary `input` or, if the primary input fails with the given `exceptionType`, from the result provided by the `fallback`.
`static <V,X extends Throwable> ListenableFuture<V>`	`catchingAsync(ListenableFuture<? extends V> input, Class<X> exceptionType, AsyncFunction<? super X,? extends V> fallback)` Deprecated. Use the overload that requires an executor. For identical behavior, pass `MoreExecutors.directExecutor()`, but consider whether another executor would be safer, as discussed in the `ListenableFuture.addListener` documentation. This method is scheduled to be removed in April 2018.
`static <V,X extends Throwable> ListenableFuture<V>`	`catchingAsync(ListenableFuture<? extends V> input, Class<X> exceptionType, AsyncFunction<? super X,? extends V> fallback, Executor executor)` Returns a `Future` whose result is taken from the given primary `input` or, if the primary input fails with the given `exceptionType`, from the result provided by the `fallback`.
`static <V> ListenableFuture<V>`	`dereference(ListenableFuture<? extends ListenableFuture<? extends V>> nested)` Deprecated. Use `submitAsync(AsyncCallable, Executor)` or `SettableFuture.setFuture(com.google.common.util.concurrent.ListenableFuture<? extends V>)` instead. Or, if you're dereferencing the output of `transform(com.google.common.util.concurrent.ListenableFuture<I>, com.google.common.base.Function<? super I, ? extends O>)` or `catching(com.google.common.util.concurrent.ListenableFuture<? extends V>, java.lang.Class<X>, com.google.common.base.Function<? super X, ? extends V>)`, switch to `transformAsync(com.google.common.util.concurrent.ListenableFuture<I>, com.google.common.util.concurrent.AsyncFunction<? super I, ? extends O>)` or `catchingAsync(com.google.common.util.concurrent.ListenableFuture<? extends V>, java.lang.Class<X>, com.google.common.util.concurrent.AsyncFunction<? super X, ? extends V>)` (and likewise for similar APIs). If the cancellation of this method's output future races with completion of the outer input future, cancellation may not be propagated to the inner input future. This method is scheduled to be removed in January 2018.
`static <V,X extends Exception> V`	`getChecked(Future<V> future, Class<X> exceptionClass)` Returns the result of `Future.get()`, converting most exceptions to a new instance of the given checked exception type.
`static <V,X extends Exception> V`	`getChecked(Future<V> future, Class<X> exceptionClass, long timeout, TimeUnit unit)` Returns the result of `Future.get(long, TimeUnit)`, converting most exceptions to a new instance of the given checked exception type.
`static <V> V`	`getDone(Future<V> future)` Returns the result of the input `Future`, which must have already completed.
`static <V> V`	`getUnchecked(Future<V> future)` Returns the result of calling `Future.get()` uninterruptibly on a task known not to throw a checked exception.
`static <V> ListenableFuture<V>`	`immediateCancelledFuture()` Creates a `ListenableFuture` which is cancelled immediately upon construction, so that `isCancelled()` always returns `true`.
`static <V,X extends Exception> CheckedFuture<V,X>`	`immediateCheckedFuture(V value)` Deprecated. `CheckedFuture` cannot properly support the chained operations that are the primary goal of `ListenableFuture`. `CheckedFuture` also encourages users to rethrow exceptions from one thread in another thread, producing misleading stack traces. Additionally, it has a surprising policy about which exceptions to map and which to leave untouched. Guava users who want a `CheckedFuture` can fork the classes for their own use, possibly specializing them to the particular exception type they use. We recommend that most people use `ListenableFuture` and perform any exception wrapping themselves. This method is scheduled for removal from Guava in February 2018.
`static <V,X extends Exception> CheckedFuture<V,X>`	`immediateFailedCheckedFuture(X exception)` Deprecated. `CheckedFuture` cannot properly support the chained operations that are the primary goal of `ListenableFuture`. `CheckedFuture` also encourages users to rethrow exceptions from one thread in another thread, producing misleading stack traces. Additionally, it has a surprising policy about which exceptions to map and which to leave untouched. Guava users who want a `CheckedFuture` can fork the classes for their own use, possibly specializing them to the particular exception type they use. We recommend that most people use `ListenableFuture` and perform any exception wrapping themselves. This method is scheduled for removal from Guava in February 2018.
`static <V> ListenableFuture<V>`	`immediateFailedFuture(Throwable throwable)` Returns a `ListenableFuture` which has an exception set immediately upon construction.
`static <V> ListenableFuture<V>`	`immediateFuture(V value)` Creates a `ListenableFuture` which has its value set immediately upon construction.
`static <T> ImmutableList<ListenableFuture<T>>`	`inCompletionOrder(Iterable<? extends ListenableFuture<? extends T>> futures)` Returns a list of delegate futures that correspond to the futures received in the order that they complete.
`static <I,O> Future<O>`	`lazyTransform(Future<I> input, Function<? super I,? extends O> function)` Like `transform(ListenableFuture, Function, Executor)` except that the transformation `function` is invoked on each call to `get()` on the returned future.
`static <V,X extends Exception> CheckedFuture<V,X>`	`makeChecked(ListenableFuture<V> future, Function<? super Exception,X> mapper)` Deprecated. `CheckedFuture` cannot properly support the chained operations that are the primary goal of `ListenableFuture`. `CheckedFuture` also encourages users to rethrow exceptions from one thread in another thread, producing misleading stack traces. Additionally, it has a surprising policy about which exceptions to map and which to leave untouched. Guava users who want a `CheckedFuture` can fork the classes for their own use, possibly specializing them to the particular exception type they use. We recommend that most people use `ListenableFuture` and perform any exception wrapping themselves. This method is scheduled for removal from Guava in February 2018.
`static <V> ListenableFuture<V>`	`nonCancellationPropagating(ListenableFuture<V> future)` Returns a `ListenableFuture` whose result is set from the supplied future when it completes.
`static <O> ListenableFuture<O>`	`scheduleAsync(AsyncCallable<O> callable, long delay, TimeUnit timeUnit, ScheduledExecutorService executorService)` Schedules `callable` on the specified `executor`, returning a `Future`.
`static <O> ListenableFuture<O>`	`submitAsync(AsyncCallable<O> callable, Executor executor)` Executes `callable` on the specified `executor`, returning a `Future`.
`static <V> ListenableFuture<List<V>>`	`successfulAsList(Iterable<? extends ListenableFuture<? extends V>> futures)` Creates a new `ListenableFuture` whose value is a list containing the values of all its successful input futures.
`static <V> ListenableFuture<List<V>>`	`successfulAsList(ListenableFuture<? extends V>... futures)` Creates a new `ListenableFuture` whose value is a list containing the values of all its successful input futures.
`static <I,O> ListenableFuture<O>`	`transform(ListenableFuture<I> input, Function<? super I,? extends O> function)` Deprecated. Use the overload that requires an executor. For identical behavior, pass `MoreExecutors.directExecutor()`, but consider whether another executor would be safer, as discussed in the `ListenableFuture.addListener` documentation. This method is scheduled to be removed in April 2018.
`static <I,O> ListenableFuture<O>`	`transform(ListenableFuture<I> input, Function<? super I,? extends O> function, Executor executor)` Returns a new `Future` whose result is derived from the result of the given `Future`.
`static <I,O> ListenableFuture<O>`	`transformAsync(ListenableFuture<I> input, AsyncFunction<? super I,? extends O> function)` Deprecated. Use the overload that requires an executor. For identical behavior, pass `MoreExecutors.directExecutor()`, but consider whether another executor would be safer, as discussed in the `ListenableFuture.addListener` documentation. This method is scheduled to be removed in April 2018.
`static <I,O> ListenableFuture<O>`	`transformAsync(ListenableFuture<I> input, AsyncFunction<? super I,? extends O> function, Executor executor)` Returns a new `Future` whose result is asynchronously derived from the result of the given `Future`.
`static <V> Futures.FutureCombiner<V>`	`whenAllComplete(Iterable<? extends ListenableFuture<? extends V>> futures)` Creates a `Futures.FutureCombiner` that processes the completed futures whether or not they're successful.
`static <V> Futures.FutureCombiner<V>`	`whenAllComplete(ListenableFuture<? extends V>... futures)` Creates a `Futures.FutureCombiner` that processes the completed futures whether or not they're successful.
`static <V> Futures.FutureCombiner<V>`	`whenAllSucceed(Iterable<? extends ListenableFuture<? extends V>> futures)` Creates a `Futures.FutureCombiner` requiring that all passed in futures are successful.
`static <V> Futures.FutureCombiner<V>`	`whenAllSucceed(ListenableFuture<? extends V>... futures)` Creates a `Futures.FutureCombiner` requiring that all passed in futures are successful.
`static <V> ListenableFuture<V>`	`withTimeout(ListenableFuture<V> delegate, long time, TimeUnit unit, ScheduledExecutorService scheduledExecutor)` Returns a future that delegates to another but will finish early (via a `TimeoutException` wrapped in an `ExecutionException`) if the specified duration expires.

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

- Method Detail
 - makeChecked
```
@Deprecated
 @GwtIncompatible
public static <V,X extends Exception> CheckedFuture<V,X> makeChecked(ListenableFuture<V> future,
 Function<? super Exception,X> mapper)
```
 Deprecated. CheckedFuture cannot properly support the chained operations that are the primary goal of ListenableFuture. CheckedFuture also encourages users to rethrow exceptions from one thread in another thread, producing misleading stack traces. Additionally, it has a surprising policy about which exceptions to map and which to leave untouched. Guava users who want a CheckedFuture can fork the classes for their own use, possibly specializing them to the particular exception type they use. We recommend that most people use ListenableFuture and perform any exception wrapping themselves. This method is scheduled for removal from Guava in February 2018.
 
 Creates a CheckedFuture out of a normal ListenableFuture and a Function that maps from Exception instances into the appropriate checked type.
 Warning: We recommend against using CheckedFuture in new projects. CheckedFuture is difficult to build libraries atop. CheckedFuture ports of methods like transformAsync(com.google.common.util.concurrent.ListenableFuture, com.google.common.util.concurrent.AsyncFunction<? super I, ? extends O>) have historically had bugs, and some of these bugs are necessary, unavoidable consequences of the CheckedFuture API. Additionally, CheckedFuture encourages users to take exceptions from one thread and rethrow them in another, producing confusing stack traces.
 The given mapping function will be applied to an InterruptedException, a CancellationException, or an ExecutionException. See Future.get() for details on the exceptions thrown.
 
 Since:
 
 9.0 (source-compatible since 1.0)
 - immediateFuture
```
public static <V> ListenableFuture<V> immediateFuture(@NullableDecl
 V value)
```
 Creates a ListenableFuture which has its value set immediately upon construction. The getters just return the value. This Future can't be canceled or timed out and its isDone() method always returns true.
 - immediateCheckedFuture
```
@Deprecated
 @GwtIncompatible
public static <V,X extends Exception> CheckedFuture<V,X> immediateCheckedFuture(@NullableDecl
 V value)
```
 Deprecated. CheckedFuture cannot properly support the chained operations that are the primary goal of ListenableFuture. CheckedFuture also encourages users to rethrow exceptions from one thread in another thread, producing misleading stack traces. Additionally, it has a surprising policy about which exceptions to map and which to leave untouched. Guava users who want a CheckedFuture can fork the classes for their own use, possibly specializing them to the particular exception type they use. We recommend that most people use ListenableFuture and perform any exception wrapping themselves. This method is scheduled for removal from Guava in February 2018.
 
 Returns a CheckedFuture which has its value set immediately upon construction.
 The returned Future can't be cancelled, and its isDone() method always returns true. Calling get() or checkedGet() will immediately return the provided value.
 - immediateFailedFuture
```
public static <V> ListenableFuture<V> immediateFailedFuture(Throwable throwable)
```
 Returns a ListenableFuture which has an exception set immediately upon construction.
 The returned Future can't be cancelled, and its isDone() method always returns true. Calling get() will immediately throw the provided Throwable wrapped in an ExecutionException.
 - immediateCancelledFuture
```
public static <V> ListenableFuture<V> immediateCancelledFuture()
```
 Creates a ListenableFuture which is cancelled immediately upon construction, so that isCancelled() always returns true.
 
 Since:
 
 14.0
 - immediateFailedCheckedFuture
```
@Deprecated
 @GwtIncompatible
public static <V,X extends Exception> CheckedFuture<V,X> immediateFailedCheckedFuture(X exception)
```
 Deprecated. CheckedFuture cannot properly support the chained operations that are the primary goal of ListenableFuture. CheckedFuture also encourages users to rethrow exceptions from one thread in another thread, producing misleading stack traces. Additionally, it has a surprising policy about which exceptions to map and which to leave untouched. Guava users who want a CheckedFuture can fork the classes for their own use, possibly specializing them to the particular exception type they use. We recommend that most people use ListenableFuture and perform any exception wrapping themselves. This method is scheduled for removal from Guava in February 2018.
 
 Returns a CheckedFuture which has an exception set immediately upon construction.
 The returned Future can't be cancelled, and its isDone() method always returns true. Calling get() will immediately throw the provided Exception wrapped in an ExecutionException, and calling checkedGet() will throw the provided exception itself.
 - submitAsync
```
public static <O> ListenableFuture<O> submitAsync(AsyncCallable<O> callable,
 Executor executor)
```
 Executes callable on the specified executor, returning a Future.
 
 Throws:
 
 RejectedExecutionException - if the task cannot be scheduled for execution
 
 Since:
 
 23.0
 - scheduleAsync
```
@GwtIncompatible
public static <O> ListenableFuture<O> scheduleAsync(AsyncCallable<O> callable,
 long delay,
 TimeUnit timeUnit,
 ScheduledExecutorService executorService)
```
 Schedules callable on the specified executor, returning a Future.
 
 Throws:
 
 RejectedExecutionException - if the task cannot be scheduled for execution
 
 Since:
 
 23.0
 - catching
```
@Deprecated
 @Partially.GwtIncompatible(value="AVAILABLE but requires exceptionType to be Throwable.class")
public static <V,X extends Throwable> ListenableFuture<V> catching(ListenableFuture<? extends V> input,
 Class<X> exceptionType,
 Function<? super X,? extends V> fallback)
```
 Deprecated. Use the overload that requires an executor. For identical behavior, pass MoreExecutors.directExecutor(), but consider whether another executor would be safer, as discussed in the ListenableFuture.addListener documentation. This method is scheduled to be removed in April 2018.
 Returns a Future whose result is taken from the given primary input or, if the primary input fails with the given exceptionType, from the result provided by the fallback. Function.apply(F) is not invoked until the primary input has failed, so if the primary input succeeds, it is never invoked. If, during the invocation of fallback, an exception is thrown, this exception is used as the result of the output Future.
 Usage example:
```
 ListenableFuture<Integer> fetchCounterFuture = ...;

 // Falling back to a zero counter in case an exception happens when
 // processing the RPC to fetch counters.
 ListenableFuture<Integer> faultTolerantFuture = Futures.catching(
 fetchCounterFuture, FetchException.class, x -> 0);
 
```
 This overload, which does not accept an executor, uses directExecutor, a dangerous choice in some cases. See the discussion in the ListenableFuture.addListener documentation. All its warnings about heavyweight listeners are also applicable to heavyweight functions passed to this method.
 Parameters:
 
 input - the primary input Future
 
 exceptionType - the exception type that triggers use of fallback. The exception type is matched against the input's exception. "The input's exception" means the cause of the ExecutionException thrown by input.get() or, if get() throws a different kind of exception, that exception itself. To avoid hiding bugs and other unrecoverable errors, callers should prefer more specific types, avoiding Throwable.class in particular.
 
 fallback - the Function to be called if input fails with the expected exception type. The function's argument is the input's exception. "The input's exception" means the cause of the ExecutionException thrown by input.get() or, if get() throws a different kind of exception, that exception itself.
 
 Since:
 
 19.0
 - catching
```
@Partially.GwtIncompatible(value="AVAILABLE but requires exceptionType to be Throwable.class")
public static <V,X extends Throwable> ListenableFuture<V> catching(ListenableFuture<? extends V> input,
 Class<X> exceptionType,
 Function<? super X,? extends V> fallback,
 Executor executor)
```
 Returns a Future whose result is taken from the given primary input or, if the primary input fails with the given exceptionType, from the result provided by the fallback. Function.apply(F) is not invoked until the primary input has failed, so if the primary input succeeds, it is never invoked. If, during the invocation of fallback, an exception is thrown, this exception is used as the result of the output Future.
 Usage example:
```
 ListenableFuture<Integer> fetchCounterFuture = ...;

 // Falling back to a zero counter in case an exception happens when
 // processing the RPC to fetch counters.
 ListenableFuture<Integer> faultTolerantFuture = Futures.catching(
 fetchCounterFuture, FetchException.class, x -> 0, directExecutor());
 
```
 When selecting an executor, note that directExecutor is dangerous in some cases. See the discussion in the ListenableFuture.addListener documentation. All its warnings about heavyweight listeners are also applicable to heavyweight functions passed to this method.
 Parameters:
 
 input - the primary input Future
 
 exceptionType - the exception type that triggers use of fallback. The exception type is matched against the input's exception. "The input's exception" means the cause of the ExecutionException thrown by input.get() or, if get() throws a different kind of exception, that exception itself. To avoid hiding bugs and other unrecoverable errors, callers should prefer more specific types, avoiding Throwable.class in particular.
 
 fallback - the Function to be called if input fails with the expected exception type. The function's argument is the input's exception. "The input's exception" means the cause of the ExecutionException thrown by input.get() or, if get() throws a different kind of exception, that exception itself.
 
 executor - the executor that runs fallback if input fails
 
 Since:
 
 19.0
 - catchingAsync
```
@CanIgnoreReturnValue
 @Deprecated
 @Partially.GwtIncompatible(value="AVAILABLE but requires exceptionType to be Throwable.class")
public static <V,X extends Throwable> ListenableFuture<V> catchingAsync(ListenableFuture<? extends V> input,
 Class<X> exceptionType,
 AsyncFunction<? super X,? extends V> fallback)
```
 Deprecated. Use the overload that requires an executor. For identical behavior, pass MoreExecutors.directExecutor(), but consider whether another executor would be safer, as discussed in the ListenableFuture.addListener documentation. This method is scheduled to be removed in April 2018.
 Returns a Future whose result is taken from the given primary input or, if the primary input fails with the given exceptionType, from the result provided by the fallback. AsyncFunction.apply(I) is not invoked until the primary input has failed, so if the primary input succeeds, it is never invoked. If, during the invocation of fallback, an exception is thrown, this exception is used as the result of the output Future.
 Usage examples:
```
 ListenableFuture<Integer> fetchCounterFuture = ...;

 // Falling back to a zero counter in case an exception happens when
 // processing the RPC to fetch counters.
 ListenableFuture<Integer> faultTolerantFuture = Futures.catchingAsync(
 fetchCounterFuture, FetchException.class, x -> immediateFuture(0));
 
```
 The fallback can also choose to propagate the original exception when desired:
```
 ListenableFuture<Integer> fetchCounterFuture = ...;

 // Falling back to a zero counter only in case the exception was a
 // TimeoutException.
 ListenableFuture<Integer> faultTolerantFuture = Futures.catchingAsync(
 fetchCounterFuture,
 FetchException.class,
 e -> {
 if (omitDataOnFetchFailure) {
 return immediateFuture(0);
 }
 throw e;
 });
 
```
 This overload, which does not accept an executor, uses directExecutor, a dangerous choice in some cases. See the discussion in the ListenableFuture.addListener documentation. All its warnings about heavyweight listeners are also applicable to heavyweight functions passed to this method. (Specifically, directExecutor functions should avoid heavyweight operations inside AsyncFunction.apply. Any heavyweight operations should occur in other threads responsible for completing the returned Future.)
 Parameters:
 
 input - the primary input Future
 
 exceptionType - the exception type that triggers use of fallback. The exception type is matched against the input's exception. "The input's exception" means the cause of the ExecutionException thrown by input.get() or, if get() throws a different kind of exception, that exception itself. To avoid hiding bugs and other unrecoverable errors, callers should prefer more specific types, avoiding Throwable.class in particular.
 
 fallback - the AsyncFunction to be called if input fails with the expected exception type. The function's argument is the input's exception. "The input's exception" means the cause of the ExecutionException thrown by input.get() or, if get() throws a different kind of exception, that exception itself.
 
 Since:
 
 19.0 (similar functionality in 14.0 as withFallback)
 - catchingAsync
```
@CanIgnoreReturnValue
 @Partially.GwtIncompatible(value="AVAILABLE but requires exceptionType to be Throwable.class")
public static <V,X extends Throwable> ListenableFuture<V> catchingAsync(ListenableFuture<? extends V> input,
 Class<X> exceptionType,
 AsyncFunction<? super X,? extends V> fallback,
 Executor executor)
```
 Returns a Future whose result is taken from the given primary input or, if the primary input fails with the given exceptionType, from the result provided by the fallback. AsyncFunction.apply(I) is not invoked until the primary input has failed, so if the primary input succeeds, it is never invoked. If, during the invocation of fallback, an exception is thrown, this exception is used as the result of the output Future.
 Usage examples:
```
 ListenableFuture<Integer> fetchCounterFuture = ...;

 // Falling back to a zero counter in case an exception happens when
 // processing the RPC to fetch counters.
 ListenableFuture<Integer> faultTolerantFuture = Futures.catchingAsync(
 fetchCounterFuture, FetchException.class, x -> immediateFuture(0), directExecutor());
 
```
 The fallback can also choose to propagate the original exception when desired:
```
 ListenableFuture<Integer> fetchCounterFuture = ...;

 // Falling back to a zero counter only in case the exception was a
 // TimeoutException.
 ListenableFuture<Integer> faultTolerantFuture = Futures.catchingAsync(
 fetchCounterFuture,
 FetchException.class,
 e -> {
 if (omitDataOnFetchFailure) {
 return immediateFuture(0);
 }
 throw e;
 },
 directExecutor());
 
```
 When selecting an executor, note that directExecutor is dangerous in some cases. See the discussion in the ListenableFuture.addListener documentation. All its warnings about heavyweight listeners are also applicable to heavyweight functions passed to this method. (Specifically, directExecutor functions should avoid heavyweight operations inside AsyncFunction.apply. Any heavyweight operations should occur in other threads responsible for completing the returned Future.)
 Parameters:
 
 input - the primary input Future
 
 exceptionType - the exception type that triggers use of fallback. The exception type is matched against the input's exception. "The input's exception" means the cause of the ExecutionException thrown by input.get() or, if get() throws a different kind of exception, that exception itself. To avoid hiding bugs and other unrecoverable errors, callers should prefer more specific types, avoiding Throwable.class in particular.
 
 fallback - the AsyncFunction to be called if input fails with the expected exception type. The function's argument is the input's exception. "The input's exception" means the cause of the ExecutionException thrown by input.get() or, if get() throws a different kind of exception, that exception itself.
 
 executor - the executor that runs fallback if input fails
 
 Since:
 
 19.0 (similar functionality in 14.0 as withFallback)
 - withTimeout
```
@GwtIncompatible
public static <V> ListenableFuture<V> withTimeout(ListenableFuture<V> delegate,
 long time,
 TimeUnit unit,
 ScheduledExecutorService scheduledExecutor)
```
 Returns a future that delegates to another but will finish early (via a TimeoutException wrapped in an ExecutionException) if the specified duration expires.
 The delegate future is interrupted and cancelled if it times out.
 
 Parameters:
 
 delegate - The future to delegate to.
 
 time - when to timeout the future
 
 unit - the time unit of the time parameter
 
 scheduledExecutor - The executor service to enforce the timeout.
 
 Since:
 
 19.0
 - transformAsync
```
@Deprecated
public static <I,O> ListenableFuture<O> transformAsync(ListenableFuture input,
 AsyncFunction<? super I,? extends O> function)
```
 Deprecated. Use the overload that requires an executor. For identical behavior, pass MoreExecutors.directExecutor(), but consider whether another executor would be safer, as discussed in the ListenableFuture.addListener documentation. This method is scheduled to be removed in April 2018.
 Returns a new Future whose result is asynchronously derived from the result of the given Future. If the given Future fails, the returned Future fails with the same exception (and the function is not invoked).
 More precisely, the returned Future takes its result from a Future produced by applying the given AsyncFunction to the result of the original Future. Example usage:
```
 ListenableFuture<RowKey> rowKeyFuture = indexService.lookUp(query);
 ListenableFuture<QueryResult> queryFuture =
 transformAsync(rowKeyFuture, dataService::readFuture);
 
```
 This overload, which does not accept an executor, uses directExecutor, a dangerous choice in some cases. See the discussion in the ListenableFuture.addListener documentation. All its warnings about heavyweight listeners are also applicable to heavyweight functions passed to this method. (Specifically, directExecutor functions should avoid heavyweight operations inside AsyncFunction.apply. Any heavyweight operations should occur in other threads responsible for completing the returned Future.)
 The returned Future attempts to keep its cancellation state in sync with that of the input future and that of the future returned by the function. That is, if the returned Future is cancelled, it will attempt to cancel the other two, and if either of the other two is cancelled, the returned Future will receive a callback in which it will attempt to cancel itself.
 Parameters:
 
 input - The future to transform
 
 function - A function to transform the result of the input future to the result of the output future
 
 Returns:
 
 A future that holds result of the function (if the input succeeded) or the original input's failure (if not)
 
 Since:
 
 19.0 (in 11.0 as transform)
 - transformAsync
```
public static <I,O> ListenableFuture<O> transformAsync(ListenableFuture input,
 AsyncFunction<? super I,? extends O> function,
 Executor executor)
```
 Returns a new Future whose result is asynchronously derived from the result of the given Future. If the given Future fails, the returned Future fails with the same exception (and the function is not invoked).
 More precisely, the returned Future takes its result from a Future produced by applying the given AsyncFunction to the result of the original Future. Example usage:
```
 ListenableFuture<RowKey> rowKeyFuture = indexService.lookUp(query);
 ListenableFuture<QueryResult> queryFuture =
 transformAsync(rowKeyFuture, dataService::readFuture, executor);
 
```
 When selecting an executor, note that directExecutor is dangerous in some cases. See the discussion in the ListenableFuture.addListener documentation. All its warnings about heavyweight listeners are also applicable to heavyweight functions passed to this method. (Specifically, directExecutor functions should avoid heavyweight operations inside AsyncFunction.apply. Any heavyweight operations should occur in other threads responsible for completing the returned Future.)
 The returned Future attempts to keep its cancellation state in sync with that of the input future and that of the future returned by the chain function. That is, if the returned Future is cancelled, it will attempt to cancel the other two, and if either of the other two is cancelled, the returned Future will receive a callback in which it will attempt to cancel itself.
 Parameters:
 
 input - The future to transform
 
 function - A function to transform the result of the input future to the result of the output future
 
 executor - Executor to run the function in.
 
 Returns:
 
 A future that holds result of the function (if the input succeeded) or the original input's failure (if not)
 
 Since:
 
 19.0 (in 11.0 as transform)
 - transform
```
@Deprecated
public static <I,O> ListenableFuture<O> transform(ListenableFuture input,
 Function<? super I,? extends O> function)
```
 Deprecated. Use the overload that requires an executor. For identical behavior, pass MoreExecutors.directExecutor(), but consider whether another executor would be safer, as discussed in the ListenableFuture.addListener documentation. This method is scheduled to be removed in April 2018.
 Returns a new Future whose result is derived from the result of the given Future. If input fails, the returned Future fails with the same exception (and the function is not invoked). Example usage:
```
 ListenableFuture<QueryResult> queryFuture = ...;
 ListenableFuture<List<Row>> rowsFuture =
 transform(queryFuture, QueryResult::getRows);
 
```
 This overload, which does not accept an executor, uses directExecutor, a dangerous choice in some cases. See the discussion in the ListenableFuture.addListener documentation. All its warnings about heavyweight listeners are also applicable to heavyweight functions passed to this method.
 The returned Future attempts to keep its cancellation state in sync with that of the input future. That is, if the returned Future is cancelled, it will attempt to cancel the input, and if the input is cancelled, the returned Future will receive a callback in which it will attempt to cancel itself.
 An example use of this method is to convert a serializable object returned from an RPC into a POJO.
 Parameters:
 
 input - The future to transform
 
 function - A Function to transform the results of the provided future to the results of the returned future. This will be run in the thread that notifies input it is complete.
 
 Returns:
 
 A future that holds result of the transformation.
 
 Since:
 
 9.0 (in 1.0 as compose)
 - transform
```
public static <I,O> ListenableFuture<O> transform(ListenableFuture input,
 Function<? super I,? extends O> function,
 Executor executor)
```
 Returns a new Future whose result is derived from the result of the given Future. If input fails, the returned Future fails with the same exception (and the function is not invoked). Example usage:
```
 ListenableFuture<QueryResult> queryFuture = ...;
 ListenableFuture<List<Row>> rowsFuture =
 transform(queryFuture, QueryResult::getRows, executor);
 
```
 When selecting an executor, note that directExecutor is dangerous in some cases. See the discussion in the ListenableFuture.addListener documentation. All its warnings about heavyweight listeners are also applicable to heavyweight functions passed to this method.
 The returned Future attempts to keep its cancellation state in sync with that of the input future. That is, if the returned Future is cancelled, it will attempt to cancel the input, and if the input is cancelled, the returned Future will receive a callback in which it will attempt to cancel itself.
 An example use of this method is to convert a serializable object returned from an RPC into a POJO.
 Parameters:
 
 input - The future to transform
 
 function - A Function to transform the results of the provided future to the results of the returned future.
 
 executor - Executor to run the function in.
 
 Returns:
 
 A future that holds result of the transformation.
 
 Since:
 
 9.0 (in 2.0 as compose)
 - lazyTransform
```
@GwtIncompatible
public static <I,O> Future<O> lazyTransform(Future input,
 Function<? super I,? extends O> function)
```
 Like transform(ListenableFuture, Function, Executor) except that the transformation function is invoked on each call to get() on the returned future.
 The returned Future reflects the input's cancellation state directly, and any attempt to cancel the returned Future is likewise passed through to the input Future.
 Note that calls to timed get only apply the timeout to the execution of the underlying Future, not to the execution of the transformation function.
 The primary audience of this method is callers of transform who don't have a ListenableFuture available and do not mind repeated, lazy function evaluation.
 
 Parameters:
 
 input - The future to transform
 
 function - A Function to transform the results of the provided future to the results of the returned future.
 
 Returns:
 
 A future that returns the result of the transformation.
 
 Since:
 
 10.0
 - dereference
```
@Deprecated
public static <V> ListenableFuture<V> dereference(ListenableFuture<? extends ListenableFuture<? extends V>> nested)
```
 Deprecated. Use submitAsync(AsyncCallable, Executor) or SettableFuture.setFuture(com.google.common.util.concurrent.ListenableFuture<? extends V>) instead. Or, if you're dereferencing the output of transform(com.google.common.util.concurrent.ListenableFuture, com.google.common.base.Function<? super I, ? extends O>) or catching(com.google.common.util.concurrent.ListenableFuture<? extends V>, java.lang.Class<X>, com.google.common.base.Function<? super X, ? extends V>), switch to transformAsync(com.google.common.util.concurrent.ListenableFuture, com.google.common.util.concurrent.AsyncFunction<? super I, ? extends O>) or catchingAsync(com.google.common.util.concurrent.ListenableFuture<? extends V>, java.lang.Class<X>, com.google.common.util.concurrent.AsyncFunction<? super X, ? extends V>) (and likewise for similar APIs). If the cancellation of this method's output future races with completion of the outer input future, cancellation may not be propagated to the inner input future. This method is scheduled to be removed in January 2018.
 Returns a new ListenableFuture whose result is the product of calling get() on the Future nested within the given Future, effectively chaining the futures one after the other. Example:
```
 SettableFuture<ListenableFuture<String>> nested = SettableFuture.create();
 ListenableFuture<String> dereferenced = dereference(nested);
 
```
 Most users will not need this method. To create a Future that completes with the result of another Future, create a SettableFuture, and call setFuture(otherFuture) on it.
 dereference has the same cancellation and execution semantics as transformAsync(ListenableFuture, AsyncFunction, Executor), in that the returned Future attempts to keep its cancellation state in sync with both the input Future and the nested Future. The transformation is very lightweight and therefore takes place in the same thread (either the thread that called dereference, or the thread in which the dereferenced future completes).
 Parameters:
 
 nested - The nested future to transform.
 
 Returns:
 
 A future that holds result of the inner future.
 
 Since:
 
 13.0
 - allAsList
```
@Beta
 @SafeVarargs
public static <V> ListenableFuture<List<V>> allAsList(ListenableFuture<? extends V>... futures)
```
 Creates a new ListenableFuture whose value is a list containing the values of all its input futures, if all succeed.
 The list of results is in the same order as the input list.
 Canceling this future will attempt to cancel all the component futures, and if any of the provided futures fails or is canceled, this one is, too.
 
 Parameters:
 
 futures - futures to combine
 
 Returns:
 
 a future that provides a list of the results of the component futures
 
 Since:
 
 10.0
 - allAsList
```
@Beta
public static <V> ListenableFuture<List<V>> allAsList(Iterable<? extends ListenableFuture<? extends V>> futures)
```
 Creates a new ListenableFuture whose value is a list containing the values of all its input futures, if all succeed.
 The list of results is in the same order as the input list.
 Canceling this future will attempt to cancel all the component futures, and if any of the provided futures fails or is canceled, this one is, too.
 
 Parameters:
 
 futures - futures to combine
 
 Returns:
 
 a future that provides a list of the results of the component futures
 
 Since:
 
 10.0
 - whenAllComplete
```
@SafeVarargs
public static <V> Futures.FutureCombiner<V> whenAllComplete(ListenableFuture<? extends V>... futures)
```
 Creates a Futures.FutureCombiner that processes the completed futures whether or not they're successful.
 
 Since:
 
 20.0
 - whenAllComplete
```
public static <V> Futures.FutureCombiner<V> whenAllComplete(Iterable<? extends ListenableFuture<? extends V>> futures)
```
 Creates a Futures.FutureCombiner that processes the completed futures whether or not they're successful.
 
 Since:
 
 20.0
 - whenAllSucceed
```
@SafeVarargs
public static <V> Futures.FutureCombiner<V> whenAllSucceed(ListenableFuture<? extends V>... futures)
```
 Creates a Futures.FutureCombiner requiring that all passed in futures are successful.
 If any input fails, the returned future fails immediately.
 
 Since:
 
 20.0
 - whenAllSucceed
```
public static <V> Futures.FutureCombiner<V> whenAllSucceed(Iterable<? extends ListenableFuture<? extends V>> futures)
```
 Creates a Futures.FutureCombiner requiring that all passed in futures are successful.
 If any input fails, the returned future fails immediately.
 
 Since:
 
 20.0
 - nonCancellationPropagating
```
public static <V> ListenableFuture<V> nonCancellationPropagating(ListenableFuture<V> future)
```
 Returns a ListenableFuture whose result is set from the supplied future when it completes. Cancelling the supplied future will also cancel the returned future, but cancelling the returned future will have no effect on the supplied future.
 
 Since:
 
 15.0
 - successfulAsList
```
@Beta
 @SafeVarargs
public static <V> ListenableFuture<List<V>> successfulAsList(ListenableFuture<? extends V>... futures)
```
 Creates a new ListenableFuture whose value is a list containing the values of all its successful input futures. The list of results is in the same order as the input list, and if any of the provided futures fails or is canceled, its corresponding position will contain null (which is indistinguishable from the future having a successful value of null).
 Canceling this future will attempt to cancel all the component futures.
 
 Parameters:
 
 futures - futures to combine
 
 Returns:
 
 a future that provides a list of the results of the component futures
 
 Since:
 
 10.0
 - successfulAsList
```
@Beta
public static <V> ListenableFuture<List<V>> successfulAsList(Iterable<? extends ListenableFuture<? extends V>> futures)
```
 Creates a new ListenableFuture whose value is a list containing the values of all its successful input futures. The list of results is in the same order as the input list, and if any of the provided futures fails or is canceled, its corresponding position will contain null (which is indistinguishable from the future having a successful value of null).
 Canceling this future will attempt to cancel all the component futures.
 
 Parameters:
 
 futures - futures to combine
 
 Returns:
 
 a future that provides a list of the results of the component futures
 
 Since:
 
 10.0
 - inCompletionOrder
```
@Beta
public static <T> ImmutableList<ListenableFuture<T>> inCompletionOrder(Iterable<? extends ListenableFuture<? extends T>> futures)
```
 Returns a list of delegate futures that correspond to the futures received in the order that they complete. Delegate futures return the same value or throw the same exception as the corresponding input future returns/throws.
 "In the order that they complete" means, for practical purposes, about what you would expect, but there are some subtleties. First, we do guarantee that, if the output future at index n is done, the output future at index n-1 is also done. (But as usual with futures, some listeners for future n may complete before some for future n-1.) However, it is possible, if one input completes with result X and another later with result Y, for Y to come before X in the output future list. (Such races are impossible to solve without global synchronization of all future completions. And they should have little practical impact.)
 Cancelling a delegate future propagates to input futures once all the delegates complete, either from cancellation or because an input future has completed. If N futures are passed in, and M delegates are cancelled, the remaining M input futures will be cancelled once N - M of the input futures complete. If all the delegates are cancelled, all the input futures will be too.
 
 Since:
 
 17.0
 - addCallback
```
@Deprecated
public static <V> void addCallback(ListenableFuture<V> future,
 FutureCallback<? super V> callback)
```
 Deprecated. Use the overload that requires an executor. For identical behavior, pass MoreExecutors.directExecutor(), but consider whether another executor would be safer, as discussed in the ListenableFuture.addListener documentation. This method is scheduled to be removed in April 2018.
 Registers separate success and failure callbacks to be run when the Future's computation is complete or, if the computation is already complete, immediately.
 There is no guaranteed ordering of execution of callbacks, but any callback added through this method is guaranteed to be called once the computation is complete.
 Example:
```
 ListenableFuture<QueryResult> future = ...;
 addCallback(future,
 new FutureCallback<QueryResult>() {
 public void onSuccess(QueryResult result) {
 storeInCache(result);
 }
 public void onFailure(Throwable t) {
 reportError(t);
 }
 });
 
```
 This overload, which does not accept an executor, uses directExecutor, a dangerous choice in some cases. See the discussion in the ListenableFuture.addListener documentation. All its warnings about heavyweight listeners are also applicable to heavyweight callbacks passed to this method.
 For a more general interface to attach a completion listener to a Future, see addListener.
 Parameters:
 
 future - The future attach the callback to.
 
 callback - The callback to invoke when future is completed.
 
 Since:
 
 10.0
 - addCallback
```
public static <V> void addCallback(ListenableFuture<V> future,
 FutureCallback<? super V> callback,
 Executor executor)
```
 Registers separate success and failure callbacks to be run when the Future's computation is complete or, if the computation is already complete, immediately.
 The callback is run on executor. There is no guaranteed ordering of execution of callbacks, but any callback added through this method is guaranteed to be called once the computation is complete.
 Example:
```
 ListenableFuture<QueryResult> future = ...;
 Executor e = ...
 addCallback(future,
 new FutureCallback<QueryResult>() {
 public void onSuccess(QueryResult result) {
 storeInCache(result);
 }
 public void onFailure(Throwable t) {
 reportError(t);
 }
 }, e);
 
```
 When selecting an executor, note that directExecutor is dangerous in some cases. See the discussion in the ListenableFuture.addListener documentation. All its warnings about heavyweight listeners are also applicable to heavyweight callbacks passed to this method.
 For a more general interface to attach a completion listener to a Future, see addListener.
 Parameters:
 
 future - The future attach the callback to.
 
 callback - The callback to invoke when future is completed.
 
 executor - The executor to run callback when the future completes.
 
 Since:
 
 10.0
 - getDone
```
@CanIgnoreReturnValue
public static <V> V getDone(Future<V> future)
 throws ExecutionException
```
 Returns the result of the input Future, which must have already completed.
 The benefits of this method are twofold. First, the name "getDone" suggests to readers that the Future is already done. Second, if buggy code calls getDone on a Future that is still pending, the program will throw instead of block. This can be important for APIs like whenAllComplete(...).call(...), where it is easy to use a new input from the call implementation but forget to add it to the arguments of whenAllComplete.
 If you are looking for a method to determine whether a given Future is done, use the instance method Future.isDone().
 
 Throws:
 
 ExecutionException - if the Future failed with an exception
 
 CancellationException - if the Future was cancelled
 
 IllegalStateException - if the Future is not done
 
 Since:
 
 20.0
 - getChecked
```
@CanIgnoreReturnValue
 @GwtIncompatible
public static <V,X extends Exception> V getChecked(Future<V> future,
 Class<X> exceptionClass)
 throws X extends Exception
```
 Returns the result of Future.get(), converting most exceptions to a new instance of the given checked exception type. This reduces boilerplate for a common use of Future in which it is unnecessary to programmatically distinguish between exception types or to extract other information from the exception instance.
 Exceptions from Future.get are treated as follows:
 - Any ExecutionException has its cause wrapped in an X if the cause is a checked exception, an UncheckedExecutionException if the cause is a RuntimeException, or an ExecutionError if the cause is an Error.
 - Any InterruptedException is wrapped in an X (after restoring the interrupt).
 - Any CancellationException is propagated untouched, as is any other RuntimeException (though get implementations are discouraged from throwing such exceptions).
 The overall principle is to continue to treat every checked exception as a checked exception, every unchecked exception as an unchecked exception, and every error as an error. In addition, the cause of any ExecutionException is wrapped in order to ensure that the new stack trace matches that of the current thread.
 Instances of exceptionClass are created by choosing an arbitrary public constructor that accepts zero or more arguments, all of type String or Throwable (preferring constructors with at least one String) and calling the constructor via reflection. If the exception did not already have a cause, one is set by calling Throwable.initCause(Throwable) on it. If no such constructor exists, an IllegalArgumentException is thrown.
 Throws:
 
 X - if get throws any checked exception except for an ExecutionException whose cause is not itself a checked exception
 
 UncheckedExecutionException - if get throws an ExecutionException with a RuntimeException as its cause
 
 ExecutionError - if get throws an ExecutionException with an Error as its cause
 
 CancellationException - if get throws a CancellationException
 
 IllegalArgumentException - if exceptionClass extends RuntimeException or does not have a suitable constructor
 
 X extends Exception
 
 Since:
 
 19.0 (in 10.0 as get)
 - getChecked
```
@CanIgnoreReturnValue
 @GwtIncompatible
public static <V,X extends Exception> V getChecked(Future<V> future,
 Class<X> exceptionClass,
 long timeout,
 TimeUnit unit)
 throws X extends Exception
```
 Returns the result of Future.get(long, TimeUnit), converting most exceptions to a new instance of the given checked exception type. This reduces boilerplate for a common use of Future in which it is unnecessary to programmatically distinguish between exception types or to extract other information from the exception instance.
 Exceptions from Future.get are treated as follows:
 - Any ExecutionException has its cause wrapped in an X if the cause is a checked exception, an UncheckedExecutionException if the cause is a RuntimeException, or an ExecutionError if the cause is an Error.
 - Any InterruptedException is wrapped in an X (after restoring the interrupt).
 - Any TimeoutException is wrapped in an X.
 - Any CancellationException is propagated untouched, as is any other RuntimeException (though get implementations are discouraged from throwing such exceptions).
 The overall principle is to continue to treat every checked exception as a checked exception, every unchecked exception as an unchecked exception, and every error as an error. In addition, the cause of any ExecutionException is wrapped in order to ensure that the new stack trace matches that of the current thread.
 Instances of exceptionClass are created by choosing an arbitrary public constructor that accepts zero or more arguments, all of type String or Throwable (preferring constructors with at least one String) and calling the constructor via reflection. If the exception did not already have a cause, one is set by calling Throwable.initCause(Throwable) on it. If no such constructor exists, an IllegalArgumentException is thrown.
 Throws:
 
 X - if get throws any checked exception except for an ExecutionException whose cause is not itself a checked exception
 
 UncheckedExecutionException - if get throws an ExecutionException with a RuntimeException as its cause
 
 ExecutionError - if get throws an ExecutionException with an Error as its cause
 
 CancellationException - if get throws a CancellationException
 
 IllegalArgumentException - if exceptionClass extends RuntimeException or does not have a suitable constructor
 
 X extends Exception
 
 Since:
 
 19.0 (in 10.0 as get and with different parameter order)
 - getUnchecked
```
@CanIgnoreReturnValue
public static <V> V getUnchecked(Future<V> future)
```
 Returns the result of calling Future.get() uninterruptibly on a task known not to throw a checked exception. This makes Future more suitable for lightweight, fast-running tasks that, barring bugs in the code, will not fail. This gives it exception-handling behavior similar to that of ForkJoinTask.join.
 Exceptions from Future.get are treated as follows:
 - Any ExecutionException has its cause wrapped in an UncheckedExecutionException (if the cause is an Exception) or ExecutionError (if the cause is an Error).
 - Any InterruptedException causes a retry of the get call. The interrupt is restored before getUnchecked returns.
 - Any CancellationException is propagated untouched. So is any other RuntimeException (get implementations are discouraged from throwing such exceptions).
 The overall principle is to eliminate all checked exceptions: to loop to avoid InterruptedException, to pass through CancellationException, and to wrap any exception from the underlying computation in an UncheckedExecutionException or ExecutionError.
 For an uninterruptible get that preserves other exceptions, see Uninterruptibles.getUninterruptibly(Future).
 Throws:
 
 UncheckedExecutionException - if get throws an ExecutionException with an Exception as its cause
 
 ExecutionError - if get throws an ExecutionException with an Error as its cause
 
 CancellationException - if get throws a CancellationException
 
 Since:
 
 10.0

Class Futures

Nested Class Summary

Method Summary

Methods inherited from class java.lang.Object

Method Detail

makeChecked

immediateFuture

immediateCheckedFuture

immediateFailedFuture

immediateCancelledFuture

immediateFailedCheckedFuture

submitAsync

scheduleAsync

catching

catching

catchingAsync

catchingAsync

withTimeout

transformAsync

transformAsync

transform

transform

lazyTransform

dereference

allAsList

allAsList

whenAllComplete

whenAllComplete

whenAllSucceed

whenAllSucceed

nonCancellationPropagating

successfulAsList

successfulAsList

inCompletionOrder

addCallback

addCallback

getDone

getChecked

getChecked

getUnchecked