chandrasekhar4u · July 29, 2014 08:06 · Nov 23, 2011
diff --git a/ListenableFuturesTest.java b/ListenableFuturesTest.java
@@ -0,0 +1,129 @@
+
+
+import com.google.common.util.concurrent.*;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.concurrent.Callable;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Created by IntelliJ IDEA.
+ * User: bbejeck
+ * Date: 11/21/11
+ * Time: 10:50 PM
+ */
+
+
+public class ListenableFuturesTest {
+
+    private ListeningExecutorService executorService;
+    private CountDownLatch startSignal;
+    private CountDownLatch endSignal;
+    private static final int NUM_THREADS = 5;
+    private boolean callbackRan;
+
+
+    @Before
+    public void setUp() {
+        executorService = MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(NUM_THREADS));
+        startSignal = new CountDownLatch(1);
+        endSignal = new CountDownLatch(1);
+        callbackRan = false;
+
+    }
+
+    @After
+    public void tearDown() {
+        executorService.shutdownNow();
+    }
+
+    @Test
+    public void testRunListenableFutureWithCallback() throws Exception {
+        ListenableFuture<String> futureTask = executorService.submit(new Task());
+        futureTask.addListener(new Runnable() {
+            @Override
+            public void run() {
+                callbackRan = true;
+                endSignal.countDown();
+            }
+        }, executorService);
+
+        endSignal.await();
+        assertThat(callbackRan, is(true));
+    }
+
+    @Test
+    public void testRunListenableFutureWithFutureCallbackSuccess() throws Exception {
+        ListenableFuture<String> futureTask = executorService.submit(new Task(startSignal));
+        FutureCallbackImpl callback = new FutureCallbackImpl();
+        Futures.addCallback(futureTask, callback);
+        startSignal.countDown();
+        endSignal.await();
+        assertThat(callback.getCallbackResult(), is("Task Done successfully"));
+    }
+
+    @Test
+    public void testRunListenableFutureWithFutureCallbackFailure() throws Exception {
+        ListenableFuture<String> futureTask = executorService.submit(new Task(null));
+        FutureCallbackImpl callback = new FutureCallbackImpl();
+        Futures.addCallback(futureTask, callback);
+        //startSignal.countDown();  don't call countdown
+        endSignal.await();
+        assertThat(callback.getCallbackResult(), is("java.lang.NullPointerException"));
+    }
+
+
+    private class FutureCallbackImpl implements FutureCallback<String> {
+
+        private StringBuilder builder = new StringBuilder();
+
+        @Override
+        public void onSuccess(String result) {
+            builder.append(result).append(" successfully");
+            done();
+
+        }
+
+        @Override
+        public void onFailure(Throwable t) {
+            builder.append(t.toString());
+            done();
+        }
+
+        private void done() {
+            endSignal.countDown();
+        }
+
+        public String getCallbackResult() {
+            return builder.toString();
+        }
+    }
+
+
+    private class Task implements Callable<String> {
+        private CountDownLatch start;
+
+        public Task() {
+        }
+
+        public Task(CountDownLatch start) {
+            this.start = start;
+        }
+
+        @Override
+        public String call() throws Exception {
+            this.start.await(1, TimeUnit.SECONDS);
+            Thread.sleep(1000);
+            return "Task Done";
+        }
+    }
+
+
+}
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