av.ref
Class StrongSoftReference<T>

java.lang.Object
  java.lang.ref.Reference<T>
      java.lang.ref.SoftReference<T>
          av.ref.StrongSoftReference<T>

Type Parameters:

T -

All Implemented Interfaces:

Reference<T>

public class StrongSoftReference<T>
extends SoftReference<T>
implements Reference<T>

This class inherits behaviors from SoftReference, whereas an instance will keep a strong reference to the referent at construction, thus prevent it from being automatically cleared by gc until the strong reference is explicitly cleared later. When later the strong protection is not required any more, invocation to clearStrong() will clear the strong reference and make the referent possiblily reach softly reachable state then subsequently the soft reference also cleared by gc and finally the referent get garbage collected. But the gc is not immediately clearing the soft reference right after the strong reference has been cleared. Meanwhile, there are still chances to restore the strong reference by invoking ensureStrong(). If it returns true, the strong reference has been successfully restored, and the referent is again under protection from being discarded by gc. The other case is the soft reference has already been cleared , it will cause subsquent invocations to SoftReference.get() keep returning null, and there's no way to get the referent back any more.

Author:

Compl

Constructor Summary

StrongSoftReference(T referent)

StrongSoftReference(T referent, ReferenceQueue<T> q)

Method Summary

void	clearStrong() Clear the strong reference to the referent to allow it to get softly reachable state thus further eligible for garbage collection.
boolean	ensureStrong() Try to restore the strong reference if it has ever been cleared by prior invocation to clearStrong().

Methods inherited from class java.lang.ref.SoftReference

get

Methods inherited from class java.lang.ref.Reference

clear, enqueue, isEnqueued

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface av.ref.Reference

clear, get

Constructor Detail

StrongSoftReference

public StrongSoftReference(T referent)

StrongSoftReference

public StrongSoftReference(T referent,
                           ReferenceQueue<T> q)

Method Detail

clearStrong

public void clearStrong()

Clear the strong reference to the referent to allow it to get softly reachable state thus further eligible for garbage collection.

ensureStrong

public boolean ensureStrong()

Try to restore the strong reference if it has ever been cleared by prior invocation to clearStrong(). If it has never been cleared, return true directly.

Returns:

whether the referent is strong referenced after this invocation.