From c60c8705060224c6f606cb7428747278638e3945 Mon Sep 17 00:00:00 2001
From: Andrew Morgan <andrew.morgan@opencredo.com>
Date: Wed, 18 Jan 2017 22:50:56 +0000
Subject: [PATCH] BAEL-613

---
 .../countdownlatch/BrokenWorker.java          | 23 +++++++
 .../concurrent/countdownlatch/Worker.java     | 22 +++++++
 .../CountdownLatchExampleTest.java            | 64 +++++++++++++++++++
 3 files changed, 109 insertions(+)
 create mode 100644 core-java/src/main/java/com/baeldung/concurrent/countdownlatch/BrokenWorker.java
 create mode 100644 core-java/src/main/java/com/baeldung/concurrent/countdownlatch/Worker.java
 create mode 100644 core-java/src/test/java/com/baeldung/concurrent/countdownlatch/CountdownLatchExampleTest.java

diff --git a/core-java/src/main/java/com/baeldung/concurrent/countdownlatch/BrokenWorker.java b/core-java/src/main/java/com/baeldung/concurrent/countdownlatch/BrokenWorker.java
new file mode 100644
index 0000000000..90cd01b69f
--- /dev/null
+++ b/core-java/src/main/java/com/baeldung/concurrent/countdownlatch/BrokenWorker.java
@@ -0,0 +1,23 @@
+package com.baeldung.concurrent.countdownlatch;
+
+import java.util.List;
+import java.util.concurrent.CountDownLatch;
+
+public class BrokenWorker implements Runnable {
+    private final List<String> outputScraper;
+    private final CountDownLatch countDownLatch;
+
+    public BrokenWorker(final List<String> outputScraper, final CountDownLatch countDownLatch) {
+        this.outputScraper = outputScraper;
+        this.countDownLatch = countDownLatch;
+    }
+
+    @Override
+    public void run() {
+        if (true) {
+            throw new RuntimeException("Oh dear");
+        }
+        countDownLatch.countDown();
+        outputScraper.add("Counted down");
+    }
+}
diff --git a/core-java/src/main/java/com/baeldung/concurrent/countdownlatch/Worker.java b/core-java/src/main/java/com/baeldung/concurrent/countdownlatch/Worker.java
new file mode 100644
index 0000000000..4701f26530
--- /dev/null
+++ b/core-java/src/main/java/com/baeldung/concurrent/countdownlatch/Worker.java
@@ -0,0 +1,22 @@
+package com.baeldung.concurrent.countdownlatch;
+
+import java.util.List;
+import java.util.concurrent.CountDownLatch;
+
+public class Worker implements Runnable {
+    private final List<String> outputScraper;
+    private final CountDownLatch countDownLatch;
+
+    public Worker(final List<String> outputScraper, final CountDownLatch countDownLatch) {
+        this.outputScraper = outputScraper;
+        this.countDownLatch = countDownLatch;
+    }
+
+    @Override
+    public void run() {
+        // Do some work
+        System.out.println("Doing some logic");
+        countDownLatch.countDown();
+        outputScraper.add("Counted down");
+    }
+}
diff --git a/core-java/src/test/java/com/baeldung/concurrent/countdownlatch/CountdownLatchExampleTest.java b/core-java/src/test/java/com/baeldung/concurrent/countdownlatch/CountdownLatchExampleTest.java
new file mode 100644
index 0000000000..9aa574a067
--- /dev/null
+++ b/core-java/src/test/java/com/baeldung/concurrent/countdownlatch/CountdownLatchExampleTest.java
@@ -0,0 +1,64 @@
+package com.baeldung.concurrent.countdownlatch;
+
+import org.assertj.core.api.Assertions;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.stream.Stream;
+
+import static java.util.stream.Collectors.toList;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class CountdownLatchExampleTest {
+    @Test
+    public void shouldBlockUntilLatchIsReleased() throws InterruptedException {
+
+        // Given
+        List<String> outputScraper = Collections.synchronizedList(new ArrayList<>());
+        CountDownLatch countDownLatch = new CountDownLatch(5);
+        List<Thread> workers = Stream
+          .generate(() -> new Thread(new Worker(outputScraper, countDownLatch)))
+          .limit(5)
+          .collect(toList());
+
+        // When
+        workers.forEach(Thread::start);
+        countDownLatch.await(); // Block until workers finish
+        outputScraper.add("Latch released");
+
+        // Then
+        outputScraper.forEach(Object::toString);
+        assertThat(outputScraper)
+          .containsExactly(
+            "Counted down",
+            "Counted down",
+            "Counted down",
+            "Counted down",
+            "Counted down",
+            "Latch released"
+          );
+    }
+
+    @Test
+    public void shouldEventuallyTimeout() throws InterruptedException {
+        // Given
+        List<String> outputScraper = Collections.synchronizedList(new ArrayList<>());
+        CountDownLatch countDownLatch = new CountDownLatch(5);
+        List<Thread> workers = Stream
+          .generate(() -> new Thread(new BrokenWorker(outputScraper, countDownLatch)))
+          .limit(5)
+          .collect(toList());
+
+        // When
+        workers.forEach(Thread::start);
+        final boolean result = countDownLatch.await(3L, TimeUnit.SECONDS);
+
+        // Then
+        assertThat(result).isTrue();
+    }
+}
\ No newline at end of file