The most efficient but thread safe list / set

Question

There are many different collections in Java designed for concurrency and thread safety, and I am at a loss as to which one to choose for my situation.

Several threads can call .add() and .remove() , and I will copy this list often with something like List<T> newList = new ArrayList<T>(concurrentList) . I will never iterate over a parallel list.

I thought of something like CopyOnWriteArrayList , but I read that it can be very inefficient because it copies itself every time it changes. I hope to find a good compromise between safety and efficiency.

What is the best list (or set) for this situation?

Answer 1

As @SpiderPig said, the best scenario with List would be an immutable, single-linked list.

However, looking at what is being done here, List not required (comment by @bhspencer). A ConcurrentSkipListSet will work most efficiently (@augray).

This answer dedicated to the topic gives more information about the pros and cons of various parallel collections.

Answer 2

You might want to find out if ctrie is suitable for your use case - it has thread-safe add and remove operations and a “copy” (in fact, snapshot) data structure works in O (1). I know two implementations of the JVM data structure: one implementation , two implementations .

Answer 3

 Collections.newSetFromMap(new ConcurrentHashMap<...>()) 

As a rule, a normal set is executed (HashSet is a truly modified shell on top of the HashMap). It offers both performance advantages / concurrecy from ConcurrentHashMap, and it does not have additional features such as ConcurrentSkipListSet (orders), COW lists (copying each modification) or parallel queues (FIFO / LIFO ordering).

Edit: I did not see @bhspencer's comment on the original post, apologizing for the theft of the spotlight.

Answer 4

Hash hash hash will be better than List. Add the latter and delete first will be fine with LinkedList. Search will be fast in arraylist based on array index.

Thanks,