什么java列表适合addAll和clear上的线程安全

Question

I only call addAll and clear of the List, but need it to thread-safe, is there any existing List for this ? Thanks

Answer 1

List is not-synchronized. So it is not thread-safe. If you want it as thread-safe means it is possible to make the list as thread-safe, you can use the

Collections.synchronizedList(List list)

Answer 2

A list created using Collections.synchronizedList(List list) will satisfy those requirements, provided that the synchronized list is the target object in the addAll(...) call, and never the parameter.

If the synchronized list (created as above) is the argument, then the problem is that addAll(list) iterates the argument list , and iterating a synchronized list is not atomic. If another thread updates list while it is being added, the you are liable to get a ConcurrentModificationException .

If you need to do the addAll(list) in a thread-safe fashion in the face of concurrent updates to list , then you need to make list a CopyOnWriteArrayList .

Answer 3

There is a concurrent list implementation in java.util.concurrent. CopyOnWriteArrayList in particular.

Answer 4

如果要使用现有列表作为同步列表，请访问Collections.synchronizedList(list)或创建目标列表，然后可以使用CopyOnWriteArrayList

Answer 5

CopyOnWriteArrayList is a concurrent replacement for synchronizedList that offers better concurrency in some common situations & eliminates the need to lock or copy the collection during iteration.

The copy on write collections derive their thread safety from the fact that as an effectively immutable object is properly published, no further synchronization is required when accessing it. They implement mutability by creating & republishing a new copy of the collection everytime it is modified. The collection does not throw ConcurrentModificationException regardless of subsequent modifications.