Nairn — Some Possibly Useful Java Utilities

Event Bus

A publish / subscribe event bus. Subscribers can register an interest to a type of event. When a publisher publishes that type the subscriber is notified. There are two versions, single and multi-threaded. The single threaded version calls subscribers on the same thread as the publisher. The multi-threaded version calls subscribers on a thread pool.

Hashpool

A collection of one thread thread-pools. A pool is selected based on a hash of an identifier passed in the the execute method. Useful when used in conjunction with the Event Bus — subscribers for a given object will always run on the same thread.

Throttler

Two Consumer implementations which throttle calls to the accept() method. Clients specify the desired throttle rate, e.g. five calls per second. ThrottledConsumer drops all calls made outside the throttle rate while ThrottledBufferedConsumer maintains a backlog that gets drained when the system is quiet.

Ring Buffer

A circular FIFO array which overwrites older values as the array loops around. Should be thread-safe, but the iterator copies the whole array which could be costly.

Cache

An implementation of the scalable, thread-safe cache from Java Concurrency in Practice.