Concurrent package classes
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The document discusses several concurrent package classes in Java: CountDownLatch, CyclicBarrier, Phaser, Exchanger, and Semaphore. CountDownLatch is used to wait for a set of tasks to complete. CyclicBarrier allows threads to wait for each other to reach a common barrier point. Phaser tracks the progress of participant threads and blocks until a certain phase is reached. Exchanger is used to exchange objects between threads. Semaphore controls access to a set of resources by acquiring and releasing permits. Examples are provided for how each class can be used.
Concurrent package classes
- 2. CountDownLatch Example How to use? 1. new CountDownLatch with count number 2. Pass CountDownLatch instance to many threads for doing something and counting down 3. Pass CountDownLatch instance to one or many threads to wait for counting down to zero 4. Thread will keep running after counting down to zero
- 4. CylicBarrier ● Call await after work finished ● Thread will wait until all thread finished
- 6. Phaser 1. Register for each threads 2. Call arrive if job of current phase finish 3. Call arriveAndAwaitAdvance if you need wait for everyone finished 4. Whenever all registered Phaser arrived, phase will advance and onAdvance method will be called
- 8. Exchanger Only one concept in Exchanger ⇒ exchange. Used to exchange object between threads.
- 10. Semaphore Number of permits to be acquired or released. 1. acquire: grab permit(s), wait until all available 2. tryAcquire: grab permit(s) until given timeout 3. release: release permit(s) 4. drainPermits: grab ALL permits 5. availablePermits: get current available permits count Reference: Semaphore.java
- 11. Semaphore Example - TicketPool
- 12. Semaphore Example - TicketGrabber
- 13. Semaphore Example - TicketSellPoint and Main