Examples of java.lang.ref.SoftReference

java.lang.ref.SoftReference
Soft reference objects, which are cleared at the discretion of the garbage collector in response to memory demand. Soft references are most often used to implement memory-sensitive caches.
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.
Direct instances of this class may be used to implement simple caches; this class or derived subclasses may also be used in larger data structures to implement more sophisticated caches. As long as the referent of a soft reference is strongly reachable, that is, is actually in use, the soft reference will not be cleared. Thus a sophisticated cache can, for example, prevent its most recently used entries from being discarded by keeping strong referents to those entries, leaving the remaining entries to be discarded at the discretion of the garbage collector. @version 1.36, 02/26/09 @author Mark Reinhold @since 1.2

    /**
     * Returns a thread local QNameCache
     */
    public static QNameCache getQNameCache ( )
    {
        SoftReference softRef = (SoftReference)_threadLocalLoaderQNameCache.get();
        QNameCache qnameCache = (QNameCache) (softRef).get();
        if (qnameCache==null)
        {
            qnameCache = new QNameCache( 32 );
            _threadLocalLoaderQNameCache.set(new SoftReference(qnameCache));
        }
        return qnameCache;
    }

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      throw new NullPointerException( "Key to get cannot be null" );
    }


    clearObsoleteReferences();


    SoftReference ref = (SoftReference) softRefCache.get( key );
    if ( ref != null ) {
      Object refValue = ref.get();
      if ( refValue != null ) {
        // This ensures recently used entries are strongly-reachable
        strongRefCache.put( key, refValue );
        return refValue;
      }

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    }


    clearObsoleteReferences();


    strongRefCache.put( key, value );
    SoftReference ref = (SoftReference) softRefCache.put(
        key,
        new KeyedSoftReference( key, value, referenceQueue )
    );


    return ( ref != null ) ? ref.get() : null;
  }

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        doTheWork(cls, ret);


        // We did it
        synchronized (this) {
            workInProgress.remove(cls);
            workDone.put(cls, new SoftReference(ret));
            notifyAll();
        }


        return ret;
    }

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    /**
     * Lookup an analysis in the fully done map.
     */
    private ContainerAnalysis lookupDone(Class cls) {
        SoftReference ref = (SoftReference) workDone.get(cls);
        if (ref == null)
            return null;
        ContainerAnalysis ret = (ContainerAnalysis) ref.get();
        if (ret == null)
            workDone.remove(cls); // clear map entry if soft ref. was cleared.
        return ret;
    }

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    }


    protected CachableRed setupCache(CachableRed img) {
        if ((lastCR == null) ||
            (img != lastCR.get())) {
            lastCR    = new SoftReference(img);
            lastCache = null;
        }


        Object o = null;
        if (lastCache != null)
            o = lastCache.get();
        if (o != null)
            return (CachableRed)o;


        img       = new TileCacheRed(img);
        lastCache = new SoftReference(img);
        return img;
    }

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        Asset result = TapestryInternalUtils.getAndDeref(cache, resource);


        if (result == null)
        {
            result = createAssetFromResource(resource);
            cache.put(resource, new SoftReference(result));
        }


        return result;
    }

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    }
  }


  protected Reference createReference(FileObject file, ReferenceQueue refqueue)
  {
    return new SoftReference(file, refqueue);
  }

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        }


        boolean shouldDestroy = !success;
        _numActive--;
        if(success) {
            _pool.add(new SoftReference(obj, refQueue));
        }
        notifyAll(); // _numActive has changed


        if (shouldDestroy && _factory != null) {
            try {

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            _factory.passivateObject(obj);
        }


        boolean shouldDestroy = !success;
        if(success) {
            _pool.add(new SoftReference(obj, refQueue));
            notifyAll(); // _numActive has changed
        }


        if(shouldDestroy) {
            try {

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