SoftReference

public class SoftReference
extends Reference<T>

java.lang.Object
↳	java.lang.ref.Reference<T>
	↳	java.lang.ref.SoftReference<T>

Soft reference objects, which are cleared at the discretion of the garbage collector in response to memory demand.

Suppose that the garbage collector determines at a certain point in time that an object is softly reachable. At that time it may choose to clear atomically all soft references to that object and all soft references to any other softly-reachable objects from which that object is reachable through a chain of strong references. At the same time or at some later time it will enqueue those newly-cleared soft references that are registered with reference queues.

All soft references to softly-reachable objects are guaranteed to have been cleared before the virtual machine throws an OutOfMemoryError. Otherwise no constraints are placed upon the time at which a soft reference will be cleared or the order in which a set of such references to different objects will be cleared. Virtual machine implementations are, however, encouraged to bias against clearing recently-created or recently-used soft references.

Avoid Soft References for Caching

In practice, soft references are inefficient for caching. The runtime doesn't have enough information on which references to clear and which to keep. Most fatally, it doesn't know what to do when given the choice between clearing a soft reference and growing the heap.

The lack of information on the value to your application of each reference limits the usefulness of soft references. References that are cleared too early cause unnecessary work; those that are cleared too late waste memory.

Most applications should use an android.util.LruCache instead of soft references. LruCache has an effective eviction policy and lets the user tune how much memory is allotted.

Summary

Public constructors
`SoftReference(T referent)` Creates a new soft reference that refers to the given object.
`SoftReference(T referent, ReferenceQueue<? super T> q)` Creates a new soft reference that refers to the given object and is registered with the given queue.

Public methods
`T`	`get()` Returns this reference object's referent.

Inherited methods

From class


        
          java.lang.ref.Reference

`void`	`clear()` Clears this reference object.
`Object`	`clone()` Throws `CloneNotSupportedException`.
`boolean`	`enqueue()` Adds this reference object to the queue with which it is registered, if any.
`T`	`get()` Returns this reference object's referent.
`boolean`	`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` 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(Object ref)` Ensures that the object referenced by the given reference remains strongly reachable, 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(T obj)` Tests if the referent of this reference object is `obj`.

From class


        
          java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(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(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()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Public constructors

SoftReference

Added in API level 1

public SoftReference (T referent)

Creates a new soft reference that refers to the given object. The new reference is not registered with any queue.

Parameters
`referent`	`T`: object the new soft reference will refer to

SoftReference

Added in API level 1

public SoftReference (T referent, 
                ReferenceQueue<? super T> q)

Creates a new soft reference that refers to the given object and is registered with the given queue.

Parameters
`referent`	`T`: object the new soft reference will refer to
`q`	`ReferenceQueue`: the queue with which the reference is to be registered, or `null` if registration is not required

Public methods

get

Added in API level 1

public T get ()

Returns this reference object's referent. If this reference object has been cleared, either by the program or by the garbage collector, then this method returns null.

Returns
`T`	The object to which this reference refers, or `null` if this reference object has been cleared