Java support for three different concurrency models

Question

I am going through different concurrency model in multi-threading environment (http://tutorials.jenkov.com/java-concurrency/concurrency-models.html)

The article

Answer 1

An excellent question to which the answer might not be quite as satisfying. The concurrency models listed show some of the ways you might want to go about implementing an concurrent system. The API provides tools used to implementing any of these models.

Lets start with ExecutorService. It allows you to submit tasks to be executed in a non-blocking way. The ThreadPoolExecutor implementation then limits the maximum number of threads available. The ExecutorService does not require the task to perform the complete process as you might expect of a parallel worker. The task may be limited to specific part of the process and send a message upon completion that starts the next step in an assembly line.

The CountDownLatch and the ExecutorService provide a means to block until all workers have completed that may come in handy if a certain process has been divided to different concurrent sub-tasks.

The point of JMS is to provide a means for messaging between components. It does not enforce a specific model for concurrency. Queues and topics denote how a message is sent from a publisher to a subscriber. When you use queues the message is sent to exactly one subscriber. Topics on the other hand broadcast the message to all subscribers of the topic.

Similar behavior could be achieved within a single component by for example using the observer pattern.

ForkJoinPool is actually one implementation of ExecutorService (which might highlight the difficulty of matching a model and an implementation detail). It just happens to be optimized for working with large amount of small tasks.

Summary: There are multiple ways to implement a certain concurrency model in the Java environment. The interfaces, classes and frameworks used in implementing a program may vary regardless of the concurrency model chosen.