Choosing the best concurrency list in Java

Question

My thread pool has a fixed number of threads  These threads need to write and read from a shared list frequently    So  which data structure  it better be a List  must be monitor-free  in java util concurrent package is best in this case

User · Answer

Any Java collection can be made to be Thread-safe like so:

List newList = Collections.synchronizedList(oldList);

Or to create a brand new thread-safe list:

List newList = Collections.synchronizedList(new ArrayList());

http://download.oracle.com/javase/6/docs/api/java/util/Collections.html#synchronizedList(java.util.List)

User · Answer

had better be List   The only List implementation in java util concurrent is CopyOnWriteArrayList  There s also the option of a synchronized list as Travis Webb mentions   That said  are you sure you need it to be a List  There are a lot more options for concurrent Queues and Maps  and you can make Sets from Maps   and those structures tend to make the most sense for many of the types of things you want to do with a shared data structure   For queues  you have a huge number of options and which is most appropriate depends on how you need to use it    ConcurrentLinkedQueue ArrayBlockingQueue LinkedBlockingDeque LinkedBlockingQueue PriorityBlockingQueue SynchronousQueue DelayQueue

User · Answer

If the size of the list if fixed  then you can use an AtomicReferenceArray  This would allow you to perform indexed updates to a slot  You could write a List view if needed

User · Answer

ConcurrentLinkedQueue uses a lock-free queue  based off the newer CAS instruction

User · Answer

If set is sufficient  ConcurrentSkipListSet might be used   Its implementation is based on ConcurrentSkipListMap which implements a skip list    The expected average time cost is log n  for the contains  add  and remove operations  the size method is not a constant-time operation

User · Answer

You might want to look at ConcurrentDoublyLinkedList written by Doug Lea based on Paul Martin s  A Practical Lock-Free Doubly-Linked List   It does not implement the java util List interface  but offers most methods you would use in a List   According to the javadoc      A concurrent linked-list implementation of a Deque    double-ended queue   Concurrent insertion  removal  and access   operations execute safely across multiple threads  Iterators are   weakly consistent  returning elements reflecting the state of   the deque at some point at or since the creation of the iterator  They   do not throw ConcurrentModificationException  and may   proceed concurrently with other operations

[java] Choosing the best concurrency list in Java

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