weak reference

GC is a thread of very low priority, so a weak reference object may not be collected immediately.

因为垃圾回收器是一个优先级很低的线程，所以弱引用对象也不一定会马上就会被回收。

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If a pointer pointing to an object not in the graph, then the object is not a reachable object, and then garbage collector sets the slot to null in the short weak reference table.

如果一个指针指向一个不在图中的对象，那么此对象就是一个不可到达的对象，垃圾收集器就将短弱引用表相应的槽置空。

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If the weak reference has been cleared ( either because the referent has already been garbage collected or because someone called WeakReference. clear()), get() returns null.

如果弱引用被清除了（不管是referent已经被垃圾收集了，还是有人调用了WeakReference.clear（）），get（）会返回null。

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A long weak reference is created.

则创建长弱引用。

provided by jukuu

Garbage collector scans the long weak reference table.

垃圾收集器扫描长弱引用表。

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If the minimum number of objects is already allocated, then a weak reference to the object is enqueued.

如果已经分配了最低数量的对象，则对象的弱引用被放置到队列中。

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On the other hand, when you create a weak reference to an object, you do not extend the lifetime of the referent at all; you simply maintain an alternate way to reach it while it is still alive.

另一方面，在创建对一个对象的弱引用时，完全没有扩展referent的生命周期，只是在对象仍然存活的时候，保持另一种到达它的方法。

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The Entry type, which is used to store the key-value mapping, extends WeakReference, so when expungeStaleEntries() asks for the next expired weak reference, it gets back an Entry.

用于存储键-值映射的Entry类型扩展了WeakReference，因此当expungeStaleEntries（）要求下一个失效的弱引用时，它得到一个Entry。

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A weak reference is a holder for a reference to an object, called the referent.

弱引用是对一个对象（称为referent）的引用的持有者。

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If a finalizer ( Final queue) is associated with a soft or weak reference, then only after the soft or weak reference is removed is the finalizer removed on the next GC pass that is run.

如果一个finalizer（Final查询）与一个soft或weak引用相关，那么只有当这个soft或weak引用删除后，这个finalizer才会在所运行的下一个GC pass上被删除。

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Using a weak reference here keeps objects that are above the minimum around as long as possible, but makes them available for GC as required.

在此使用弱引用可以使除最低数量对象以外的对象尽可能久地保持活跃状态，但是使它们可供GC根据需要使用。

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From above shall we say that an object can't have a soft reference and a weak reference at the same time?

从以上是否能看出，一个对象不能同时具有软引用和弱引用？

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The weak reference from the long-lived object to the short-lived object is kept long after the short-lived object has been destroyed.

在短周期对象销毁后，长周期对象对短周期对象的弱引用依然会长久保留下来。

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Dead mappings could be eliminated by periodically scanning the Map, calling get() on each weak reference, and removing the mapping if get() returns null.

可以通过周期性地扫描Map，对每一个弱引用调用get（），并在get（）返回null时删除那个映射而消除死映射。

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It would be nice if there was a way to be notified when the referent of a weak reference is garbage collected, and that is what reference queues are for.

如果有一种方法可以在弱引用的referent被垃圾收集时发出通知就好了，这就是引用队列的作用。

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