LinkedList Vs ConcurrentLinkedQueue

Question

Currently in a multithreaded environment, we are using a LinkedList to hold data. Sometimes in the logs we get NoSuchElementException while it is polling the linkedlist. Please

Answer 1

ConcurrentLinkedQueue [is] an unbounded, thread-safe, FIFO-ordered queue. It uses a linked structure, similar to those we saw in Section 13.2.2 as the basis for skip lists, and in Section 13.1.1 for hash table overflow chaining. We noticed there that one of the main attractions of linked structures is that the insertion and removal operations implemented by pointer rearrangements perform in constant time. This makes them especially useful as queue implementations, where these operations are always required on cells at the ends of the structure, that is, cells that do not need to be located using the slow sequential search of linked structures.

ConcurrentLinkedQueue uses a CAS-based wait-free algorithm that is, one that guarantees that any thread can always complete its current operation, regardless of the state of other threads accessing the queue. It executes queue insertion and removal operations in constant time, but requires linear time to execute size. This is because the algorithm, which relies on co-operation between threads for insertion and removal, does not keep track of the queue size and has to iterate over the queue to calculate it when it is required.

From Java Generics and Collections, ch. 14.2.

Note that ConcurrentLinkedQueue does not implement the List interface, so it suffices as a replacement for LinkedList only if the latter was used purely as a queue. In this case, ConcurrentLinkedQueue is obviously a better choice. There should be no big performance issue unless its size is frequently queried. But as a disclaimer, you can only be sure about performance if you measure it within your own concrete environment and program.