weakreference

The implementation of WeakHashMap illustrates a common idiom with weak references & that some internal object extends WeakReference .

WeakHashMap的实现展示了弱引用的一种常见用法&一些内部对象扩展WeakReference。

The referent of a WeakReference is set at construction time , and its value , if it has not yet been cleared , can be retrieved with get () .

WeakReference的referent是在构造时设置的，在没有被清除之前，可以用get（）获取它的值。

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。

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。