android - java - 带有 ArrayList 的 WeakReferences？
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android - java - WeakReferences with an ArrayList?
提问by codingNewb
I know that with a WeakReference, if I make a WeakReferenceto something that unless there's a direct reference to it that it will be Garbage Collected with the next GC cycle. My question becomes, what if I make an ArrayListof WeakReferences?
我知道使用WeakReference, 如果我WeakReference对某些东西做 a ，除非有直接引用它，否则它将在下一个 GC 循环中被垃圾收集。我的问题变成了，如果我做一个ArrayListof WeakReferences 怎么办？
For example:
例如：
ArrayList<WeakReference<String>> exArrayList;
exArrayList = new ArrayList<WeakReference<String>>();
exArrayList.add(new WeakReference<String>("Hello"));
I can now access the data with exArrayList.get(0).get().
我现在可以使用exArrayList.get(0).get().
My question becomes: This is WeakReferencedata, will the data located at exArrayList.get(0)be GC'd with the next GC cycle? (even IF I don't make another direct reference to it) or will this particular reference stick around until the arraylistis emptied? (eg: exArrayList.clear();).
我的问题变成：这是WeakReference数据，位于 的数据会exArrayList.get(0)在下一个 GC 周期中被 GC 处理吗？（即使我没有直接引用它）或者这个特定的引用会一直存在直到arraylist清空？（例如：）exArrayList.clear();。
If this is a duplicate I haven't found it with my keywords in google.
如果这是重复的，我还没有在 google 中用我的关键字找到它。
采纳答案by Evgeniy Dorofeev
exArrayList.add(new WeakReference<String>("Hello"));is a bad example becauseStringliterals are never GC-edif it were e.g.
exArrayList.add(new WeakReference<Object>(new Object()));then after a GC the object would be GC-ed, butexArrayList.get(0)would still returnWeakReference, thoughexArrayList.get(0).get()would returnnull
exArrayList.add(new WeakReference<String>("Hello"));是一个不好的例子，因为String文字永远不会被垃圾回收如果是，
exArrayList.add(new WeakReference<Object>(new Object()));那么在 GC 之后，对象将被 GC 处理，但exArrayList.get(0)仍会返回WeakReference，尽管exArrayList.get(0).get()会返回null
回答by SJuan76
The data at exArrayList.get(0)is the WeakReference. It is not by itself a weak reference, so it will not be collected...
处的数据exArrayList.get(0)是WeakReference。它本身不是弱引用，因此不会被收集......
BUT the object referenced by exArrayList.get(0)is weakly referenced, so it mightbe GCed at any time (of course, that requires that there are no strongreferences to that object).
但是被引用的对象exArrayList.get(0)是弱引用的，所以它可能随时被GCed（当然，这要求没有对该对象的强引用）。
So
所以
data.get(0)won't become null, but data.get(0).get()might become.
data.get(0)不会变成null，但data.get(0).get()可能会变成。
In other words, the list does not references the weak referenced object but the weak reference itself.
换句话说，列表不引用弱引用对象，而是引用弱引用本身。
回答by Stefan Reich
This is a bad idea as the other posters explained above (reference objects not freed). Use a WeakHashMap with the objects as keys and some dummy values ("" or Boolean.TRUE or similar).
正如上面解释的其他海报一样，这是一个坏主意（参考对象未释放）。使用 WeakHashMap 将对象作为键和一些虚拟值（"" 或 Boolean.TRUE 或类似的）。
