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

# ReferenceQueue

` public class ReferenceQueue `   
` extends https://developer.android.com/reference/java/lang/Object ` ` `

|---|---|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object) ||
| ↳ | java.lang.ref.ReferenceQueue\<T\> |

<br />

*** ** * ** ***

Reference queues, to which registered reference objects are appended by the garbage collector after the appropriate reachability changes are detected.

## Summary

| ### Public constructors ||
|---|---|
| ` https://developer.android.com/reference/java/lang/ref/ReferenceQueue#ReferenceQueue()() ` Constructs a new reference-object queue. |

| ### Public methods ||
|---|---|
| ` https://developer.android.com/reference/java/lang/ref/Reference<? extends T>` | ` https://developer.android.com/reference/java/lang/ref/ReferenceQueue#poll()() ` Polls this queue to see if a reference object is available. |
| ` https://developer.android.com/reference/java/lang/ref/Reference<? extends T>` | ` https://developer.android.com/reference/java/lang/ref/ReferenceQueue#remove(long)(long timeout) ` Removes the next reference object in this queue, blocking until either one becomes available or the given timeout period expires. |
| ` https://developer.android.com/reference/java/lang/ref/Reference<? extends T>` | ` https://developer.android.com/reference/java/lang/ref/ReferenceQueue#remove()() ` Removes the next reference object in this queue, blocking until one becomes available. |

### 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*.

## Public constructors

### ReferenceQueue

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

```
public ReferenceQueue ()
```

Constructs a new reference-object queue.

<br />

## Public methods

### poll

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

```
public Reference<? extends T> poll ()
```

Polls this queue to see if a reference object is available. If one is available without further delay then it is removed from the queue and returned. Otherwise this method immediately returns null.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/ref/Reference<? extends T>` | A reference object, if one was immediately available, otherwise `null` <br /> |

### remove

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

```
public Reference<? extends T> remove (long timeout)
```

Removes the next reference object in this queue, blocking until either one becomes available or the given timeout period expires.

This method does not offer real-time guarantees: It schedules the timeout as if by invoking the `https://developer.android.com/reference/java/lang/Object#wait(long)` method.

<br />

| Parameters ||
|---|---|
| `timeout` | `long`: If positive, block for up to `timeout` milliseconds while waiting for a reference to be added to this queue. If zero, block indefinitely. <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/ref/Reference<? extends T>` | A reference object, if one was available within the specified timeout period, otherwise `null` <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | If the value of the timeout argument is negative |
| `https://developer.android.com/reference/java/lang/InterruptedException` | If the timeout wait is interrupted |

### remove

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

```
public Reference<? extends T> remove ()
```

Removes the next reference object in this queue, blocking until one becomes available.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/lang/ref/Reference<? extends T>` | A reference object, blocking until one becomes available <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/InterruptedException` | If the wait is interrupted |