Antarmuka ExecutorService

Napa sampeyan mbutuhake antarmuka Executor?

Sadurunge Java 5, sampeyan kudu nulis kabeh manajemen thread kode dhewe ing aplikasi sampeyan. Kajaba iku, nggawe aUtas anyarobyek punika operasi sumber-intensif, lan iku ora nggawe pangertèn kanggo nggawe thread anyar kanggo saben tugas entheng. Lan amarga masalah iki wis dikenal kanggo saben pangembang aplikasi multi-Utas, padha mutusaké kanggo nggawa fungsi iki menyang Jawa minangka framework Executor .

Apa ide gedhe? Iku prasaja: tinimbang nggawe utas anyar kanggo saben tugas anyar, utas disimpen ing jenis "panyimpenan", lan nalika tugas anyar teka, kita njupuk thread sing wis ana tinimbang nggawe sing anyar.

Antarmuka utama kerangka iki yaiku Executor , ExecutorService lan ScheduledExecutorService , sing saben-saben ngluwihi fungsi sadurunge.

Antarmuka Executor minangka antarmuka dhasar. Iki nyatakake metode eksekusi void (perintah Runnable) sing ditindakake dening obyek Runnable .

Antarmuka ExecutorService luwih menarik. Wis cara kanggo ngatur completion saka karya, uga cara kanggo bali sawetara jinis asil. Ayo dipikirake kanthi luwih rinci babagan metode kasebut:

Ayo goleki conto cilik nggarap ExecutorService .

import java.util.List;
import java.util.concurrent.*;

public class ExecutorServiceTest {
   public static void main(String[] args) throws InterruptedException, ExecutionException, TimeoutException {
//Create an ExecutorService for 2 threads
       java.util.concurrent.ExecutorService executorService = new ThreadPoolExecutor(2, 2, 60, TimeUnit.SECONDS, new ArrayBlockingQueue<>(10));
// Create 5 tasks
       MyRunnable task1 = new MyRunnable();
       MyRunnable task2 = new MyRunnable();
       MyRunnable task3 = new MyRunnable();
       MyRunnable task4 = new MyRunnable();
       MyRunnable task5 = new MyRunnable();

       final List<MyRunnable> tasks = List.of(task1, task2, task3, task4, task5);
// Pass a list that contains the 5 tasks we created
       final List<Future<Void>> futures = executorService.invokeAll(tasks, 6, TimeUnit.SECONDS);
       System.out.println("Futures received");

// Stop the ExecutorService
       executorService.shutdown();

       try {
           TimeUnit.SECONDS.sleep(3);
       } catch (InterruptedException e) {
           e.printStackTrace();
       }

       System.out.println(executorService.isShutdown());
       System.out.println(executorService.isTerminated());
   }

   public static class MyRunnable implements Callable<Void> {

       @Override
       public void call() {
// Add 2 delays. When the ExecutorService is stopped, we will see which delay is in progress when the attempt is made to stop execution of the task
           try {
               TimeUnit.SECONDS.sleep(3);
           } catch (InterruptedException e) {
               System.out.println("sleep 1: " + e.getMessage());
           }
           try {
               TimeUnit.SECONDS.sleep(2);
           } catch (InterruptedException e) {
               System.out.println("sleep 2: " + e.getMessage());
           }
           System.out.println("done");
           return null;
       }
   }
}

Output:

Saben tugas mlaku 5 detik. Kita nggawe blumbang kanggo loro Utas, supaya loro baris pisanan output nggawe pangertèn sampurna.

Enem detik sawise program diwiwiti, metode invokeAll kaping metu lan asil bali minangka dhaptar Futures . Iki bisa dideleng saka output string Futures ditampa .

Sawise rong tugas pisanan rampung, loro maneh diwiwiti. Nanging amarga wektu entek sing disetel ing metode invokeAll wis entek, rong tugas iki ora duwe wektu kanggo ngrampungake. Dheweke nampa perintah "batal" . Mulane output duwe rong baris karo sleep 1: sleep interrupted .

Banjur sampeyan bisa ndeleng rong baris liyane kanthi rampung . Iki minangka efek samping sing dakkandhakake nalika nerangake metode invokeAll .

Tugas kaping lima lan pungkasan ora nate diwiwiti, mula kita ora bisa ndeleng apa-apa babagan output kasebut.

Rong baris pungkasan minangka asil nelpon metode isShutdown lan isTerminated .

Sampeyan uga menarik kanggo mbukak conto iki ing mode debug lan katon ing status tugas sawise wektu entek elapses (nyetel breakpoint ing baris karo executorService.shutdown (); ):

We ndeleng sing loro tugas Rampung biasane , lan telung tugas padha "Batal" .

ScheduledExecutorService

Kanggo ngrampungake diskusi para pelaksana, ayo deleng ing ScheduledExecutorService .

Ana 4 cara: