Skip to content

Most visited

Recently visited

navigation

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
From class java.lang.Object

Public constructors

SoftReference

Added in API level 1
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
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
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
This site uses cookies to store your preferences for site-specific language and display options.

Hooray!

This class requires API level or higher

This doc is hidden because your selected API level for the documentation is . You can change the documentation API level with the selector above the left navigation.

For more information about specifying the API level your app requires, read Supporting Different Platform Versions.

Take a one-minute survey?
Help us improve Android tools and documentation.