Java.lang.ref.WeakReference
말그대로, '약한' 참조 이다. '약한' 참조는 해당 객체에 대한 소멸을 막지 않는다. 즉, 어떤 객체에 대한 참조가 WeakReference 밖에 남아있지 않다면 그 객체는 gc(Garbage Collection)의 대상이 된다.
Original Reference
Weak reference objects, which do not prevent their referents from being made finalizable, finalized, and then reclaimed. Weak references are most often used to implement canonicalizing mappings.
Suppose that the garbage collector determines at a certain point in time that an object is weakly reachable. At that time it will atomically clear all weak references to that object and all weak references to any other weakly-reachable objects from which that object is reachable through a chain of strong and soft references. At the same time it will declare all of the formerly weakly-reachable objects to be finalizable. At the same time or at some later time it will enqueue those newly-cleared weak references that are registered with reference queues.