# WeakReference 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/WeakReference#pubctors)\|[Inherited Methods](https://developer.android.com/reference/java/lang/ref/WeakReference#inhmethods) # WeakReference ` public class WeakReference ` ` `` extends `[Reference](https://developer.android.com/reference/java/lang/ref/Reference)` `` ` |---|---|----------------------------------| | [java.lang.Object](https://developer.android.com/reference/java/lang/Object) ||| | ↳ | [java.lang.ref.Reference](https://developer.android.com/reference/java/lang/ref/Reference)\ || | | ↳ | java.lang.ref.WeakReference\ |
*** ** * ** *** Weak reference objects, which do not prevent their referents from being made finalizable, finalized, and then reclaimed. Weak references are most often used to implement canonicalizing mappings. Suppose that the garbage collector determines at a certain point in time that an object is[weakly reachable](https://docs.oracle.com/javase/8/docs/api/java/lang/ref/package-summary.html#reachability). At that time it will atomically clear all weak references to that object and all weak references to any other weakly-reachable objects from which that object is reachable through a chain of strong and soft references. At the same time it will declare all of the formerly weakly-reachable objects to be finalizable. At the same time or at some later time it will enqueue those newly-cleared weak references that are registered with reference queues. ## Summary | ### Public constructors || |------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---| | ` `[WeakReference](https://developer.android.com/reference/java/lang/ref/WeakReference#WeakReference(T))`(T referent) ` Creates a new weak reference that refers to the given object. | | ` `[WeakReference](https://developer.android.com/reference/java/lang/ref/WeakReference#WeakReference(T,%20java.lang.ref.ReferenceQueue))`(T referent, `[ReferenceQueue](https://developer.android.com/reference/java/lang/ref/ReferenceQueue)` q) ` Creates a new weak reference that refers to the given object and is registered with the given queue. | | ### Inherited methods | |-----------------------|---| | From class` `[java.lang.ref.Reference](https://developer.android.com/reference/java/lang/ref/Reference)` ` |-----------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` void` | ` `[clear](https://developer.android.com/reference/java/lang/ref/Reference#clear())`() ` Clears this reference object. | | ` `[Object](https://developer.android.com/reference/java/lang/Object) | ` `[clone](https://developer.android.com/reference/java/lang/ref/Reference#clone())`() ` Throws[CloneNotSupportedException](https://developer.android.com/reference/java/lang/CloneNotSupportedException). | | ` boolean` | ` `[enqueue](https://developer.android.com/reference/java/lang/ref/Reference#enqueue())`() ` Adds this reference object to the queue with which it is registered, if any. | | ` T` | ` `[get](https://developer.android.com/reference/java/lang/ref/Reference#get())`() ` Returns this reference object's referent. | | ` boolean` | ` `[isEnqueued](https://developer.android.com/reference/java/lang/ref/Reference#isEnqueued())`() ` *This method was deprecated in API level 31. This method was never implemented to test if a reference object has been cleared and enqueued as it was previously specified since 1.2. This method could be misused due to the inherent race condition or without an associated`ReferenceQueue`. An application relying on this method to release critical resources could cause serious performance issue. An application should use[ReferenceQueue](https://developer.android.com/reference/java/lang/ref/ReferenceQueue)to reliably determine what reference objects that have been enqueued or`refersTo(null)`to determine if this reference object has been cleared.* | | ` static void` | ` `[reachabilityFence](https://developer.android.com/reference/java/lang/ref/Reference#reachabilityFence(java.lang.Object))`(`[Object](https://developer.android.com/reference/java/lang/Object)` ref) ` Ensures that the object referenced by the given reference remains[*strongly reachable*](https://developer.android.com/reference/java/lang/ref/package-summary#reachability), regardless of any prior actions of the program that might otherwise cause the object to become unreachable; thus, the referenced object is not reclaimable by garbage collection at least until after the invocation of this method. | | ` final boolean` | ` `[refersTo](https://developer.android.com/reference/java/lang/ref/Reference#refersTo(T))`(T obj) ` Tests if the referent of this reference object is`obj`. | || | From class` `[java.lang.Object](https://developer.android.com/reference/java/lang/Object)` ` |--------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | ` `[Object](https://developer.android.com/reference/java/lang/Object) | ` `[clone](https://developer.android.com/reference/java/lang/Object#clone())`() ` Creates and returns a copy of this object. | | ` boolean` | ` `[equals](https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object))`(`[Object](https://developer.android.com/reference/java/lang/Object)` obj) ` Indicates whether some other object is "equal to" this one. | | ` void` | ` `[finalize](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 `[Class](https://developer.android.com/reference/java/lang/Class)`` | ` `[getClass](https://developer.android.com/reference/java/lang/Object#getClass())`() ` Returns the runtime class of this`Object`. | | ` int` | ` `[hashCode](https://developer.android.com/reference/java/lang/Object#hashCode())`() ` Returns a hash code value for the object. | | ` final void` | ` `[notify](https://developer.android.com/reference/java/lang/Object#notify())`() ` Wakes up a single thread that is waiting on this object's monitor. | | ` final void` | ` `[notifyAll](https://developer.android.com/reference/java/lang/Object#notifyAll())`() ` Wakes up all threads that are waiting on this object's monitor. | | ` `[String](https://developer.android.com/reference/java/lang/String) | ` `[toString](https://developer.android.com/reference/java/lang/Object#toString())`() ` Returns a string representation of the object. | | ` final void` | ` `[wait](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` | ` `[wait](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` | ` `[wait](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 ### WeakReference Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public WeakReference (T referent) ``` Creates a new weak reference that refers to the given object. The new reference is not registered with any queue.
| Parameters || |------------|---------------------------------------------------------| | `referent` | `T`: object the new weak reference will refer to
| ### WeakReference Added in[API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) ``` public WeakReference (T referent, ReferenceQueue q) ``` Creates a new weak reference that refers to the given object and is registered with the given queue.
| Parameters || |------------|--------------------------------------------------------------------------------------------------------------------------| | `referent` | `T`: object the new weak reference will refer to
| | `q` | `ReferenceQueue`: the queue with which the reference is to be registered, or`null`if registration is not required
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