Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary: [Ctors](https://developer.android.com/reference/java/util/concurrent/FutureTask#pubctors) \| [Methods](https://developer.android.com/reference/java/util/concurrent/FutureTask#pubmethods) \| [Protected Methods](https://developer.android.com/reference/java/util/concurrent/FutureTask#promethods) \| [Inherited Methods](https://developer.android.com/reference/java/util/concurrent/FutureTask#inhmethods)

# FutureTask


`
public


class
FutureTask
`


`

extends https://developer.android.com/reference/java/lang/Object


`

`


implements

https://developer.android.com/reference/java/util/concurrent/RunnableFuture<V>


`

|---|---|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object) ||
| ↳ | java.util.concurrent.FutureTask\<V\> |

<br />

*** ** * ** ***

A cancellable asynchronous computation. This class provides a base
implementation of `https://developer.android.com/reference/java/util/concurrent/Future`, with methods to start and cancel
a computation, query to see if the computation is complete, and
retrieve the result of the computation. The result can only be
retrieved when the computation has completed; the `get`
methods will block if the computation has not yet completed. Once
the computation has completed, the computation cannot be restarted
or cancelled (unless the computation is invoked using
`https://developer.android.com/reference/java/util/concurrent/FutureTask#runAndReset()`).

A `FutureTask` can be used to wrap a `https://developer.android.com/reference/java/util/concurrent/Callable` or
`https://developer.android.com/reference/java/lang/Runnable` object. Because `FutureTask` implements
`Runnable`, a `FutureTask` can be submitted to an
`https://developer.android.com/reference/java/util/concurrent/Executor` for execution.

In addition to serving as a standalone class, this class provides
`protected` functionality that may be useful when creating
customized task classes.

## Summary

| ### Public constructors ||
|---|---|
| ` https://developer.android.com/reference/java/util/concurrent/FutureTask#FutureTask(java.lang.Runnable,%20V)(https://developer.android.com/reference/java/lang/Runnable runnable, V result) ` Creates a `FutureTask` that will, upon running, execute the given `Runnable`, and arrange that `get` will return the given result on successful completion. |
| ` https://developer.android.com/reference/java/util/concurrent/FutureTask#FutureTask(java.util.concurrent.Callable<V>)(https://developer.android.com/reference/java/util/concurrent/Callable<V> callable) ` Creates a `FutureTask` that will, upon running, execute the given `Callable`. |

| ### Public methods ||
|---|---|
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#cancel(boolean)(boolean mayInterruptIfRunning) ` Attempts to cancel execution of this task. |
| ` https://developer.android.com/reference/java/lang/Throwable` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#exceptionNow()() ` Returns the exception thrown by the task, without waiting. |
| ` V` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#get(long,%20java.util.concurrent.TimeUnit)(long timeout, https://developer.android.com/reference/java/util/concurrent/TimeUnit unit) ` Waits if necessary for at most the given time for the computation to complete, and then retrieves its result, if available. |
| ` V` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#get()() ` Waits if necessary for the computation to complete, and then retrieves its result. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#isCancelled()() ` Returns `true` if this task was cancelled before it completed normally. |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#isDone()() ` Returns `true` if this task completed. |
| ` V` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#resultNow()() ` Returns the computed result, without waiting. |
| ` void` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#run()() ` Sets this Future to the result of its computation unless it has been cancelled. |
| ` https://developer.android.com/reference/java/util/concurrent/Future.State` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#state()() ` |
| ` https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#toString()() ` Returns a string representation of this FutureTask. |

| ### Protected methods ||
|---|---|
| ` void` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#done()() ` Protected method invoked when this task transitions to state `isDone` (whether normally or via cancellation). |
| ` boolean` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#runAndReset()() ` Executes the computation without setting its result, and then resets this future to initial state, failing to do so if the computation encounters an exception or is cancelled. |
| ` void` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#set(V)(V v) ` Sets the result of this future to the given value unless this future has already been set or has been cancelled. |
| ` void` | ` https://developer.android.com/reference/java/util/concurrent/FutureTask#setException(java.lang.Throwable)(https://developer.android.com/reference/java/lang/Throwable t) ` Causes this future to report an `https://developer.android.com/reference/java/util/concurrent/ExecutionException` with the given throwable as its cause, unless this future has already been set or has been cancelled. |

| ### Inherited methods |
|---|---|
| From class ` https://developer.android.com/reference/java/lang/Object ` |---|---| | ` https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/lang/Object#clone()() ` Creates and returns a copy of this object. | | ` boolean` | ` https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object obj) ` Indicates whether some other object is "equal to" this one. | | ` void` | ` https://developer.android.com/reference/java/lang/Object#finalize()() ` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. | | ` final https://developer.android.com/reference/java/lang/Class<?>` | ` https://developer.android.com/reference/java/lang/Object#getClass()() ` Returns the runtime class of this `Object`. | | ` int` | ` https://developer.android.com/reference/java/lang/Object#hashCode()() ` Returns a hash code value for the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notify()() ` Wakes up a single thread that is waiting on this object's monitor. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notifyAll()() ` Wakes up all threads that are waiting on this object's monitor. | | ` https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/lang/Object#toString()() ` Returns a string representation of the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long,%20int)(long timeoutMillis, int nanos) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long)(long timeoutMillis) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait()() ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*. | ||
| From interface ` https://developer.android.com/reference/java/util/concurrent/RunnableFuture ` |---|---| | ` abstract void` | ` https://developer.android.com/reference/java/util/concurrent/RunnableFuture#run()() ` Sets this Future to the result of its computation unless it has been cancelled. | ||
| From interface ` https://developer.android.com/reference/java/util/concurrent/Future ` |---|---| | ` abstract boolean` | ` https://developer.android.com/reference/java/util/concurrent/Future#cancel(boolean)(boolean mayInterruptIfRunning) ` Attempts to cancel execution of this task. | | ` default https://developer.android.com/reference/java/lang/Throwable` | ` https://developer.android.com/reference/java/util/concurrent/Future#exceptionNow()() ` Returns the exception thrown by the task, without waiting. | | ` abstract V` | ` https://developer.android.com/reference/java/util/concurrent/Future#get(long,%20java.util.concurrent.TimeUnit)(long timeout, https://developer.android.com/reference/java/util/concurrent/TimeUnit unit) ` Waits if necessary for at most the given time for the computation to complete, and then retrieves its result, if available. | | ` abstract V` | ` https://developer.android.com/reference/java/util/concurrent/Future#get()() ` Waits if necessary for the computation to complete, and then retrieves its result. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/concurrent/Future#isCancelled()() ` Returns `true` if this task was cancelled before it completed normally. | | ` abstract boolean` | ` https://developer.android.com/reference/java/util/concurrent/Future#isDone()() ` Returns `true` if this task completed. | | ` default V` | ` https://developer.android.com/reference/java/util/concurrent/Future#resultNow()() ` Returns the computed result, without waiting. | | ` default https://developer.android.com/reference/java/util/concurrent/Future.State` | ` https://developer.android.com/reference/java/util/concurrent/Future#state()() ` | ||
| From interface ` https://developer.android.com/reference/java/lang/Runnable ` |---|---| | ` abstract void` | ` https://developer.android.com/reference/java/lang/Runnable#run()() ` When an object implementing interface `Runnable` is used to create a thread, starting the thread causes the object's `run` method to be called in that separately executing thread. | ||

## Public constructors

### FutureTask

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public FutureTask (Runnable runnable, 
                V result)
```

Creates a `FutureTask` that will, upon running, execute the
given `Runnable`, and arrange that `get` will return the
given result on successful completion.

<br />

| Parameters ||
|---|---|
| `runnable` | `Runnable`: the runnable task <br /> |
| `result` | `V`: the result to return on successful completion. If you don't need a particular result, consider using constructions of the form: `Future<?> f = new FutureTask<Void>(runnable, null)` <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the runnable is null |

### FutureTask

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public FutureTask (Callable<V> callable)
```

Creates a `FutureTask` that will, upon running, execute the
given `Callable`.

<br />

| Parameters ||
|---|---|
| `callable` | `Callable`: the callable task <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if the callable is null |

## Public methods

### cancel

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean cancel (boolean mayInterruptIfRunning)
```

Attempts to cancel execution of this task. This method has no
effect if the task is already completed or cancelled, or could
not be cancelled for some other reason. Otherwise, if this
task has not started when `cancel` is called, this task
should never run. If the task has already started, then the
`mayInterruptIfRunning` parameter determines whether the
thread executing this task (when known by the implementation)
is interrupted in an attempt to stop the task.

The return value from this method does not necessarily
indicate whether the task is now cancelled; use `https://developer.android.com/reference/java/util/concurrent/Future#isCancelled()`.

<br />

| Parameters ||
|---|---|
| `mayInterruptIfRunning` | `boolean`: `true` if the thread executing this task should be interrupted (if the thread is known to the implementation); otherwise, in-progress tasks are allowed to complete <br /> |

| Returns ||
|---|---|
| `boolean` | `false` if the task could not be cancelled, typically because it has already completed; `true` otherwise. If two or more threads cause a task to be cancelled, then at least one of them returns `true`. Implementations may provide stronger guarantees. <br /> |

### exceptionNow

Added in [API level 36](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public Throwable exceptionNow ()
```

Returns the exception thrown by the task, without waiting.

This method is for cases where the caller knows that the task
has already completed with an exception.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/Throwable` | the exception thrown by the task <br /> |

### get

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public V get (long timeout, 
                TimeUnit unit)
```

Waits if necessary for at most the given time for the computation
to complete, and then retrieves its result, if available.

<br />

| Parameters ||
|---|---|
| `timeout` | `long`: the maximum time to wait <br /> |
| `unit` | `TimeUnit`: the time unit of the timeout argument <br /> |

| Returns ||
|---|---|
| `V` | the computed result <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/util/concurrent/CancellationException` |   |
| `https://developer.android.com/reference/java/util/concurrent/ExecutionException` |   |
| `https://developer.android.com/reference/java/lang/InterruptedException` |   |
| `https://developer.android.com/reference/java/util/concurrent/TimeoutException` |   |

### get

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public V get ()
```

Waits if necessary for the computation to complete, and then
retrieves its result.

<br />

| Returns ||
|---|---|
| `V` | the computed result <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/util/concurrent/CancellationException` |   |
| `https://developer.android.com/reference/java/util/concurrent/ExecutionException` |   |
| `https://developer.android.com/reference/java/lang/InterruptedException` |   |

### isCancelled

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean isCancelled ()
```

Returns `true` if this task was cancelled before it completed
normally.

<br />

| Returns ||
|---|---|
| `boolean` | `true` if this task was cancelled before it completed <br /> |

### isDone

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public boolean isDone ()
```

Returns `true` if this task completed.

Completion may be due to normal termination, an exception, or
cancellation -- in all of these cases, this method will return
`true`.

<br />

| Returns ||
|---|---|
| `boolean` | `true` if this task completed <br /> |

### resultNow

Added in [API level 36](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public V resultNow ()
```

Returns the computed result, without waiting.

This method is for cases where the caller knows that the task has
already completed successfully, for example when filtering a stream
of Future objects for the successful tasks and using a mapping
operation to obtain a stream of results.
`lang=java :
results = futures.stream()
.filter(f -> f.state() == Future.State.SUCCESS)
.map(Future::resultNow)
.toList();
`

<br />

| Returns ||
|---|---|
| `V` | the computed result <br /> |

### run

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public void run ()
```

Sets this Future to the result of its computation
unless it has been cancelled.

<br />

### state

Added in [API level 36](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public Future.State state ()
```

<br />

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/util/concurrent/Future.State` | the computation state <br /> |

### toString

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public String toString ()
```

Returns a string representation of this FutureTask.

<br />

##### Implementation Requirements:

- The default implementation returns a string identifying this FutureTask, as well as its completion state. The state, in brackets, contains one of the strings `"Completed Normally"`, `"Completed Exceptionally"`, `"Cancelled"`, or `"Not completed"`.

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/String` | a string representation of this FutureTask <br /> |

## Protected methods

### done

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected void done ()
```

Protected method invoked when this task transitions to state
`isDone` (whether normally or via cancellation). The
default implementation does nothing. Subclasses may override
this method to invoke completion callbacks or perform
bookkeeping. Note that you can query status inside the
implementation of this method to determine whether this task
has been cancelled.

<br />

### runAndReset

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected boolean runAndReset ()
```

Executes the computation without setting its result, and then
resets this future to initial state, failing to do so if the
computation encounters an exception or is cancelled. This is
designed for use with tasks that intrinsically execute more
than once.

<br />

| Returns ||
|---|---|
| `boolean` | `true` if successfully run and reset <br /> |

### set

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected void set (V v)
```

Sets the result of this future to the given value unless
this future has already been set or has been cancelled.

This method is invoked internally by the `https://developer.android.com/reference/java/util/concurrent/FutureTask#run()` method
upon successful completion of the computation.

<br />

| Parameters ||
|---|---|
| `v` | `V`: the value <br /> |

### setException

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected void setException (Throwable t)
```

Causes this future to report an `https://developer.android.com/reference/java/util/concurrent/ExecutionException`
with the given throwable as its cause, unless this future has
already been set or has been cancelled.

This method is invoked internally by the `https://developer.android.com/reference/java/util/concurrent/FutureTask#run()` method
upon failure of the computation.

<br />

| Parameters ||
|---|---|
| `t` | `Throwable`: the cause of failure <br /> |