ConcurrentHashMap.newKeySet() 与 Collections.newSetFromMap()

问题描述

Java 8 引入了获取并发 Set 实现的新方法

Java 8 introduced new way to obtain a concurrent Set implementation

// Pre-Java-8 way to create a concurrent set
Set<String> oldStyle = Collections.newSetFromMap(new ConcurrentHashMap<>());
// New method in Java 8
Set<String> newStyle = ConcurrentHashMap.newKeySet();

有什么理由更喜欢新方法吗?

Is there any reason to prefer new method?

有什么优点/缺点?

推荐答案

ConcurrentHashMap.newKeySet() 应该更高效一些，因为它移除了单层间接.Collections.newSetFromMap(map)主要是基于将操作重定向到map.keySet()，而ConcurrentHashMap.newKeySet()则非常接近 map.keySet() 本身(仅具有附加支持).

ConcurrentHashMap.newKeySet() should be somewhat more efficient as removes a single level of indirection. Collections.newSetFromMap(map) is mostly based on redirecting the operations to the map.keySet(), but ConcurrentHashMap.newKeySet() is very close to map.keySet() itself (just with additions support).

至于功能，我认为没有区别.

As for functionality, I see no difference.

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