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

        BreakIterator result = createBreakInstance(locale,
                                                   type,
                                                   dataName,
                                                   dictionaryName);
        BreakIteratorCache cache = new BreakIteratorCache(locale, result);
        iterCache[type] = new SoftReference(cache);
        return result;
    }

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    private static ThreadLocal encoder = new ThreadLocal();


    private static boolean warnUnsupportedCharset = true;


    private static Object deref(ThreadLocal tl) {
        SoftReference sr = (SoftReference)tl.get();
  if (sr == null)
      return null;
  return sr.get();
    }

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      return null;
  return sr.get();
    }


    private static void set(ThreadLocal tl, Object ob) {
  tl.set(new SoftReference(ob));
    }

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     */
    static Reference createReference(Object obj, boolean soft) {
  Reference ref = null;
  if (obj != null) {
      if (soft) {
    ref = new SoftReference(obj);
      } else {
    ref = new WeakReference(obj);
      }
  }
  return ref;

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  }
  method = findMethod(targetClass, methodName, argClasses);
        if (cache && method != null) {
      if (methodCache == null) {
    methodCache = new HashMap();
    methodCacheRef = new SoftReference(methodCache);
      }
            methodCache.put(signature, method);
        }
        return method;
    }

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    private static class MyThreadLocal extends ThreadLocal<SoftReference> {


        ConcurrentHashMap<String,AtomicInteger> usage = new ConcurrentHashMap<String,AtomicInteger> ();


        public ThreadCategoryInfo getInfo() {
            final SoftReference reference = get();
            ThreadCategoryInfo tcinfo;
            if (reference != null) {
                tcinfo = (ThreadCategoryInfo) reference.get();
                if( tcinfo == null ) {
                    tcinfo = new ThreadCategoryInfo();
                    set(new SoftReference(tcinfo));
                }
            }
            else {
                tcinfo = new ThreadCategoryInfo();
                set(new SoftReference(tcinfo));
            }
            return tcinfo;
        }

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            }
            return tcinfo;
        }


        public ThreadCategoryInfo getInfoNullable() {
            final SoftReference reference = get();
            return reference == null ? null : (ThreadCategoryInfo) reference.get();
        }

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        }
        
        @Override public V call(final Object... args) {
            if (queue.poll() != null) cleanUpNullReferences(cache, queue);  // if something has been evicted, do a clean-up
            final Object key = generateKey(args);
            final SoftReference reference = (SoftReference) cache.get(key);
            Object result = reference != null ? reference.get() : null;
            if (result == null) {
                result = closure.call(args);
                if (result == null) {
                    result = MEMOIZE_NULL;
                }
                cache.put(key, new SoftReference(result));
            }
            lruProtectionStorage.touch(key, result);
            return result == MEMOIZE_NULL ? null : (V) result;
        }

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        int i = 0;
        while ( i < size )
        {
            try
            {
                SoftReference ref = (SoftReference) _pool.get( i );
                buffer = (ByteBuffer) ref.get();
                if ( buffer != null && buffer.capacity() >= capacity )
                {
                    ref.clear();
                    _pool.remove( i );
                    _currentSize -= buffer.capacity();
                    buffer.limit( capacity );
                    LOG.log( Level.FINEST, "Borrowed buffer with capacity of " + buffer.capacity() + "(limit="
                            + capacity + "). Pool max size: " + _sizeB + " Current pool size: " + _currentSize );

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    {
        clean();
        if ( _currentSize <= _sizeB )
        {
            buffer.clear();
            SoftReference ref = new SoftReference( buffer, this._refQueue );
            _pool.add( ref );
            _currentSize += buffer.capacity();
            LOG.log( Level.FINEST, "Pushed back buffer with capacity of " + buffer.capacity() + ". Pool max size: "
                    + _sizeB + " Current pool size: " + _currentSize );
        }

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