问题描述
Java文档表示，映射支持方法values()和entrySet()的返回值.因此，对地图的更改会反映在集合中，反之亦然.我不希望这种情况发生在我的静态副本上.本质上，我希望在DS上完成许多并发操作.但是对于某些情况，我想遍历其静态快照.我想遍历静态快照，因为我假设与同时更新的版本相比，遍历静态快照会更快.
Java doc says that return values of method values() and entrySet() are backed by the map. So changes to the map are reflected in the set and vice versa. I don't want this to happen to my static copy. Essentially, I want lots of concurrent operations to be done on my DS. But for some cases I want to iterate over its static snapshot. I want to iterate over static snapshot, as I am assuming iterating over static snapshot will be faster as compared to a version which is being updated concurrently.
推荐答案
简单地制作一份副本，新的HashMap将与原始副本无关.
Simply make a copy, new HashMap would be independent of the original one.
Set<K> keySetCopy = new HashSet<>(map.keySet());
List<V> valuesCopy = new ArrayList<>(map.values());
但是请注意，这将对并发结构进行一次完整的迭代，但是一次只能是静态快照.因此，您将需要相当于一个完整迭代的时间.
However mind that this will take a full iteration over the concurrentStructure, once but will only then be static snapshots. So you will need time equivalent to one full iteration.
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