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。

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

youdao

一个弱引用对象将会保持一个指向一个超出作用域或者被置空的对象的引用，直到它确实被垃圾回收删除。

A weak reference object will keep a reference to an object that went out of scope or was set to null, until it is actually deleted by the garbage collector.

youdao

这些图持有弱引用，允许连接这样的被跟踪对象在只有方面引用它们的时候，被垃圾收集掉。

These maps hold weak references to allow tracked objects like connections to be garbage collected when they are referenced only by the aspect.

youdao