All Reference types are cleared before they are enqueued, so the thread handling the post-mortem cleanup never has access to the referent object, only the Reference object.
所有Reference类型在加入队列之前被清除，所以处理事后检查(post - mortem)清除的线程永远不会具有referent对象的访问权，而只具有Reference对象的访问权。
Clear: Setting the reference object's referent field to null and declaring the object in the heap that the reference class referred to as finalizable.
清除：将引用对象的referent域设置为 null ，并将引用类在堆中引用的对象声明为 可结束的。
When you copy an object reference using an ordinary (strong) reference, you constrain the lifetime of the referent to be at least as long as that of the copied reference.
用一个普通的(强)引用拷贝一个对象引用时，限制referent的生命周期至少与被拷贝的引用的生命周期一样长。
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。
The WeakReference object's referent field is set to null, thereby making it not refer to the heap object any longer.
WeakReference对象的referent 域被设置为 null ，从而使该对象不再引用heap 对象。
The SoftReference object's referent field is set to null, thereby making it not refer to the heap object any longer.
SoftReference对象的referent域被设置为null，从而使该对象不再引用heap对象。
In its semantic meaning, we can divide the referent of its subject and object into two categories, namely, the same referent and the different referent.
在语义上，主语和宾语的指称可以分为“同指”和“异指”两种类型。
In its semantic meaning, we can divide the referent of its subject and object into two categories, namely, the same referent and the different referent.
在语义上，主语和宾语的指称可以分为“同指”和“异指”两种类型。
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