Merge pull request #360 from myArea51/master

ExecutorService tutorial

core-java-8/src/test/java/com/baeldung/java8/Java8ExecutorServiceTest.java

@@ -0,0 +1,155 @@
+package com.baeldung.java8;
+
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.*;
+import static org.junit.Assert.*;
+
+
+public class Java8ExecutorServiceTest {
+
+    private Runnable runnableTask;
+    private Callable<String> callableTask;
+    private List<Callable<String>> callableTasks;
+
+    @Before
+    public void init() {
+
+        runnableTask = () -> {
+            try {
+                TimeUnit.MILLISECONDS.sleep(300);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+        };
+
+        callableTask = () -> {
+            TimeUnit.MILLISECONDS.sleep(300);
+            return "Task's execution";
+        };
+
+        callableTasks = new ArrayList<>();
+        callableTasks.add(callableTask);
+        callableTasks.add(callableTask);
+        callableTasks.add(callableTask);
+    }
+
+    @Test
+    public void creationSubmittingTaskShuttingDown_whenShutDown_thenCorrect() {
+
+        ExecutorService executorService = Executors.newFixedThreadPool(10);
+        executorService.submit(runnableTask);
+        executorService.submit(callableTask);
+        executorService.shutdown();
+
+        assertTrue(executorService.isShutdown());
+    }
+
+    @Test
+    public void creationSubmittingTasksShuttingDownNow_whenShutDownAfterAwating_thenCorrect() {
+
+        ExecutorService threadPoolExecutor =
+          new ThreadPoolExecutor(1, 1, 0L, TimeUnit.MILLISECONDS,
+            new LinkedBlockingQueue<>());
+
+        for (int i = 0; i < 100; i++) {
+            threadPoolExecutor.submit(callableTask);
+        }
+
+        List<Runnable> notExecutedTasks = smartShutdown(threadPoolExecutor);
+
+        assertTrue(threadPoolExecutor.isShutdown());
+        assertFalse(notExecutedTasks.isEmpty());
+        assertTrue(notExecutedTasks.size() > 0 && notExecutedTasks.size() < 98);
+    }
+
+    private List<Runnable> smartShutdown(ExecutorService executorService) {
+
+        List<Runnable> notExecutedTasks = new ArrayList<>();
+        executorService.shutdown();
+        try {
+            if (!executorService.awaitTermination(800, TimeUnit.MILLISECONDS)) {
+                notExecutedTasks = executorService.shutdownNow();
+            }
+        } catch (InterruptedException e) {
+            notExecutedTasks = executorService.shutdownNow();
+        }
+        return notExecutedTasks;
+    }
+
+    @Test
+    public void submittingTasks_whenExecutedOneAndAll_thenCorrect() {
+
+        ExecutorService executorService = Executors.newFixedThreadPool(10);
+
+        String result = null;
+        List<Future<String>> futures = new ArrayList<>();
+        try {
+            result = executorService.invokeAny(callableTasks);
+            futures = executorService.invokeAll(callableTasks);
+        } catch (InterruptedException | ExecutionException e) {
+            e.printStackTrace();
+        }
+
+        assertEquals("Task's execution", result);
+        assertTrue(futures.size() == 3);
+    }
+
+    @Test
+    public void submittingTaskShuttingDown_whenGetExpectedResult_thenCorrect() {
+
+        ExecutorService executorService = Executors.newFixedThreadPool(10);
+
+        Future<String> future = executorService.submit(callableTask);
+        String result = null;
+        try {
+            result = future.get();
+            result = future.get(200, TimeUnit.MILLISECONDS);
+        } catch (InterruptedException | ExecutionException | TimeoutException e) {
+            e.printStackTrace();
+        }
+
+        executorService.shutdown();
+
+        assertEquals("Task's execution", result);
+    }
+
+    @Test
+    public void submittingTask_whenCanceled_thenCorrect() {
+
+        ExecutorService executorService = Executors.newFixedThreadPool(10);
+
+        Future<String> future = executorService.submit(callableTask);
+
+        boolean canceled = future.cancel(true);
+        boolean isCancelled = future.isCancelled();
+
+        executorService.shutdown();
+
+        assertTrue(canceled);
+        assertTrue(isCancelled);
+    }
+
+    @Test
+    public void submittingTaskScheduling_whenExecuted_thenCorrect() {
+
+        ScheduledExecutorService executorService = Executors
+                .newSingleThreadScheduledExecutor();
+
+        Future<String> resultFuture = executorService.schedule(callableTask, 1, TimeUnit.SECONDS);
+        String result = null;
+        try {
+            result = resultFuture.get();
+        } catch (InterruptedException | ExecutionException e) {
+            e.printStackTrace();
+        }
+
+        executorService.shutdown();
+
+        assertEquals("Task's execution", result);
+    }
+}