Type Parameters:

T - the type of the value that completes the underlying Future

All Known Implementing Classes:

PromiseImpl
```
public interface Promise<T>
```
A Promise is a write-once container for a read-only Future, allowing the underlying Future to be completed with a value or an exception.
The associated Executor is used to run asynchronous handlers, for example, via promise.future().onComplete(...).
Creation

Promise provides static factory methods to create new promises:
- Unfulfilled promises: make()
- Already completed promises:
All factory methods also have variants that accept an Executor, allowing finer control over thread usage and thread pool configuration.
One-shot API

When a single Thread is responsible for completing the Promise, use one of the following methods. Calls will throw an exception if the Promise has already been completed:
API for concurrent completion

When multiple Threads may attempt to complete the Promise, use one of the following "try" methods. Calls will return false if the Promise is already completed:

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Default Methods Deprecated Methods
Modifier and Type	Method	Description
`default Promise<T>`	`complete(@NonNull Try<? extends T> value)`	Completes this `Promise` with the given `value`.
`default Promise<T>`	`completeWith(@NonNull Future<? extends T> other)`	Completes this `Promise` with the result of the given `Future` once it is completed.
`default java.util.concurrent.Executor`	`executor()`	Returns the `Executor` used by the underlying `Future` of this `Promise`.
`java.util.concurrent.ExecutorService`	`executorService()`	Deprecated. Removed starting with Vavr 0.10.0, use `executor()` instead.
`static <T> Promise<T>`	`failed(@NonNull java.lang.Throwable exception)`	Creates a `Promise` that is already completed with a failure, using the `Future.DEFAULT_EXECUTOR` for asynchronous operations.
`static <T> Promise<T>`	`failed(@NonNull java.util.concurrent.Executor executor, @NonNull java.lang.Throwable exception)`	Creates a `Promise` that is already completed with a failure, using the specified `Executor` for asynchronous operations.
`default Promise<T>`	`failure(@NonNull java.lang.Throwable exception)`	Completes this `Promise` with the given exception.
`static <T> Promise<T>`	`fromTry(@NonNull Try<? extends T> result)`	Creates a `Promise` from the given `Try`, using the `Future.DEFAULT_EXECUTOR` for asynchronous operations.
`static <T> Promise<T>`	`fromTry(@NonNull java.util.concurrent.Executor executor, @NonNull Try<? extends T> result)`	Creates a `Promise` from the given `Try`, using the specified `Executor` for asynchronous operations.
`Future<T>`	`future()`	Returns the underlying `Future` associated with this `Promise`.
`default boolean`	`isCompleted()`	Checks whether this `Promise` has been completed, either successfully or with a failure.
`static <T> Promise<T>`	`make()`	Creates a new `Promise` that is not yet completed, using the `Future.DEFAULT_EXECUTOR` (typically `ForkJoinPool.commonPool()`) for asynchronous operations.
`static <T> Promise<T>`	`make(@NonNull java.util.concurrent.Executor executor)`	Creates a new `Promise` that is not yet completed, using the specified `Executor` for asynchronous operations.
`static <T> Promise<T>`	`narrow(Promise<? extends T> promise)`	Narrows a `Promise<? extends T>` to `Promise<T>` through a type-safe cast.
`default Promise<T>`	`success(T value)`	Completes this `Promise` with the given value.
`static <T> Promise<T>`	`successful(@NonNull java.util.concurrent.Executor executor, T result)`	Creates a `Promise` that is already completed successfully, using the specified `Executor` for asynchronous operations.
`static <T> Promise<T>`	`successful(T result)`	Creates a `Promise` that is already completed successfully, using the `Future.DEFAULT_EXECUTOR` for asynchronous operations.
`boolean`	`tryComplete(@NonNull Try<? extends T> value)`	Attempts to complete this `Promise` with the given `value`.
`default Promise<T>`	`tryCompleteWith(@NonNull Future<? extends T> other)`	Attempts to complete this `Promise` with the result of the given `Future` once it is completed.
`default boolean`	`tryFailure(@NonNull java.lang.Throwable exception)`	Attempts to complete this `Promise` with the given exception.
`default boolean`	`trySuccess(T value)`	Attempts to complete this `Promise` with the given value.

- Method Detail
  - failed
```
static <T> Promise<T> failed(@NonNull java.lang.Throwable exception)
```
    Creates a Promise that is already completed with a failure, using the Future.DEFAULT_EXECUTOR for asynchronous operations.
    
    Type Parameters:
    
    T - the type of the value that would have been returned on success
    
    Parameters:
    
    exception - the cause of the failure
    
    Returns:
    
    a Promise completed with the given failure
    
    Throws:
    
    java.lang.NullPointerException - if exception is null
  - failed
```
static <T> Promise<T> failed(@NonNull java.util.concurrent.Executor executor,
                             @NonNull java.lang.Throwable exception)
```
    Creates a Promise that is already completed with a failure, using the specified Executor for asynchronous operations.
    
    Type Parameters:
    
    T - the type of the value that would have been returned on success
    
    Parameters:
    
    executor - the Executor used by the underlying Future
    
    exception - the cause of the failure
    
    Returns:
    
    a Promise completed with the given failure
    
    Throws:
    
    java.lang.NullPointerException - if executor or exception is null
  - fromTry
```
static <T> Promise<T> fromTry(@NonNull Try<? extends T> result)
```
    Creates a Promise from the given Try, using the Future.DEFAULT_EXECUTOR for asynchronous operations.
    
    Type Parameters:
    
    T - the type of the value in case of success
    
    Parameters:
    
    result - the Try representing a success or failure
    
    Returns:
    
    a Promise already completed with the given Try result
    
    Throws:
    
    java.lang.NullPointerException - if result is null
  - fromTry
```
static <T> Promise<T> fromTry(@NonNull java.util.concurrent.Executor executor,
                              @NonNull Try<? extends T> result)
```
    Creates a Promise from the given Try, using the specified Executor for asynchronous operations.
    
    Type Parameters:
    
    T - the type of the value in case of success
    
    Parameters:
    
    executor - the Executor used by the underlying Future
    
    result - the Try representing a success or failure
    
    Returns:
    
    a Promise already completed with the given Try result
    
    Throws:
    
    java.lang.NullPointerException - if executor or result is null
  - make
```
static <T> Promise<T> make()
```
    Creates a new Promise that is not yet completed, using the Future.DEFAULT_EXECUTOR (typically ForkJoinPool.commonPool()) for asynchronous operations.
    
    Type Parameters:
    
    T - the type of the value that will complete the Promise
    
    Returns:
    
    a new, uncompleted Promise
  - make
```
static <T> Promise<T> make(@NonNull java.util.concurrent.Executor executor)
```
    Creates a new Promise that is not yet completed, using the specified Executor for asynchronous operations.
    
    Type Parameters:
    
    T - the type of the value that will complete the Promise
    
    Parameters:
    
    executor - the Executor used by the underlying Future
    
    Returns:
    
    a new, uncompleted Promise
    
    Throws:
    
    java.lang.NullPointerException - if executor is null
  - narrow
```
static <T> Promise<T> narrow(Promise<? extends T> promise)
```
    Narrows a Promise<? extends T> to Promise<T> through a type-safe cast. This is safe because immutable or read-only collections are covariant.
    
    Type Parameters:
    
    T - the component type of the Promise
    
    Parameters:
    
    promise - the Promise to narrow
    
    Returns:
    
    the same promise instance, cast to Promise<T>
  - successful
```
static <T> Promise<T> successful(T result)
```
    Creates a Promise that is already completed successfully, using the Future.DEFAULT_EXECUTOR for asynchronous operations.
    
    Type Parameters:
    
    T - the type of the value
    
    Parameters:
    
    result - the value of the successful result
    
    Returns:
    
    a Promise already completed with the given result
  - successful
```
static <T> Promise<T> successful(@NonNull java.util.concurrent.Executor executor,
                                 T result)
```
    Creates a Promise that is already completed successfully, using the specified Executor for asynchronous operations.
    
    Type Parameters:
    
    T - the type of the value
    
    Parameters:
    
    executor - the Executor used by the underlying Future
    
    result - the value of the successful result
    
    Returns:
    
    a Promise already completed with the given result
    
    Throws:
    
    java.lang.NullPointerException - if executor is null
  - executor
```
default java.util.concurrent.Executor executor()
```
    Returns the Executor used by the underlying Future of this Promise.
    
    Returns:
    
    the Executor associated with this Promise
  - executorService
```
@Deprecated
java.util.concurrent.ExecutorService executorService()
```
    Deprecated.
    Removed starting with Vavr 0.10.0, use executor() instead.
    
    This method is deprecated.
    THE DEFAULT IMPLEMENTATION (obtained by one of the Promise factory methods) MIGHT THROW AN UnsupportedOperationException AT RUNTIME, DEPENDING ON WHAT Future.executorService() returns.
    
    Returns:
    
    (never)
    
    Throws:
    
    java.lang.UnsupportedOperationException - if the underlying Executor isn't an ExecutorService.
  - future
```
Future<T> future()
```
    Returns the underlying Future associated with this Promise.
    
    Returns:
    
    the underlying Future
  - isCompleted
```
default boolean isCompleted()
```
    Checks whether this Promise has been completed, either successfully or with a failure.
    
    Returns:
    
    true if the Promise is completed, false otherwise
  - complete
```
default Promise<T> complete(@NonNull Try<? extends T> value)
```
    Completes this Promise with the given value.
    
    Parameters:
    
    value - a Try.Success containing the result or a Try.Failure containing an exception
    
    Returns:
    
    this Promise
    
    Throws:
    
    java.lang.IllegalStateException - if this Promise has already been completed
  - tryComplete
```
boolean tryComplete(@NonNull Try<? extends T> value)
```
    Attempts to complete this Promise with the given value.
    
    Parameters:
    
    value - a Try.Success containing the result or a Try.Failure containing an exception
    
    Returns:
    
    true if the Promise was completed successfully, false if it was already completed
  - completeWith
```
default Promise<T> completeWith(@NonNull Future<? extends T> other)
```
    Completes this Promise with the result of the given Future once it is completed.
    
    Parameters:
    
    other - the Future whose result or failure will complete this Promise
    
    Returns:
    
    this Promise
  - tryCompleteWith
```
default Promise<T> tryCompleteWith(@NonNull Future<? extends T> other)
```
    Attempts to complete this Promise with the result of the given Future once it is completed.
    
    Parameters:
    
    other - the Future whose result or failure may complete this Promise
    
    Returns:
    
    true if this Promise was completed by other, false if it was already completed
  - success
```
default Promise<T> success(T value)
```
    Completes this Promise with the given value.
    
    Parameters:
    
    value - the value to complete this Promise with
    
    Returns:
    
    this Promise
    
    Throws:
    
    java.lang.IllegalStateException - if this Promise has already been completed
  - trySuccess
```
default boolean trySuccess(T value)
```
    Attempts to complete this Promise with the given value.
    
    Parameters:
    
    value - the value to complete this Promise with
    
    Returns:
    
    true if the Promise was completed successfully, false if it was already completed
  - failure
```
default Promise<T> failure(@NonNull java.lang.Throwable exception)
```
    Completes this Promise with the given exception.
    
    Parameters:
    
    exception - the exception to complete this Promise with
    
    Returns:
    
    this Promise
    
    Throws:
    
    java.lang.IllegalStateException - if this Promise has already been completed
  - tryFailure
```
default boolean tryFailure(@NonNull java.lang.Throwable exception)
```
    Attempts to complete this Promise with the given exception.
    
    Parameters:
    
    exception - the exception to complete this Promise with
    
    Returns:
    
    true if the Promise was completed successfully, false if it was already completed

Interface Promise<T>

Creation

One-shot API

API for concurrent completion

Method Summary

Method Detail

failed

failed

fromTry

fromTry

make

make

narrow

successful

successful

executor

executorService

future

isCompleted

complete

tryComplete

completeWith

tryCompleteWith

success

trySuccess

failure

tryFailure