JAVA concurrent

java.util.concurrent is package that provides classes/interfaces that related to concurrent execution

Important interfaces/classes

Respresent the object that can execute the given task(either current therad or another thread)

• Executor : Object that can run a given task(Runnable).
• ExecutorService : More useful method than Executor. It provides methods to summit task, then give back Future.
• ScheduledExecutorService : Can execute task given delay in future or execute periodically.
• ForkJoinPool : An ExecutorService that implement work-stealing algorithms. Thread in the pool can steal work which in the pending queue of another thread.
• Executors : The class that contains factory methods use for create Thread pool.

Wrapper of task execution result

• Future : The wrapper of execution result that may success or fail.
• CompletableFuture : Provide more extensive usecase than Future(for example Composition) ```java // Create executorService with single thread using factory method from Executors var executorService = Executors.newSingleThreadExecutor();

Callable task = () -> { System.out.println("Perform something and return value"); return 2; };

// summit task to executorService Future future = executorService.submit(task);

try { // blocking the current thead until result is done var result = future.get(); System.out.println(“the result of computation is “ + result); } catch (InterruptedException | ExecutionException e) { System.out.println(“Exception!!! “ + e); } ```

Syscronizations

• CountDownLatch : Block with await method until count reach zero.
• Phaser : Extended functionality version of CountDownLatch.
• CyclicBarrier : Extended functionality version of CountDownLatch.

Memory Synchronization

• Lock : More extensive locking mechanism that synchronized keyword
• Semaphore : Respresent the resource counting that can be acquired and released.