BAEL-613
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parent
66449db339
commit
c60c870506
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package com.baeldung.concurrent.countdownlatch;
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import java.util.List;
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import java.util.concurrent.CountDownLatch;
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public class BrokenWorker implements Runnable {
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private final List<String> outputScraper;
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private final CountDownLatch countDownLatch;
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public BrokenWorker(final List<String> outputScraper, final CountDownLatch countDownLatch) {
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this.outputScraper = outputScraper;
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this.countDownLatch = countDownLatch;
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}
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@Override
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public void run() {
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if (true) {
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throw new RuntimeException("Oh dear");
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}
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countDownLatch.countDown();
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outputScraper.add("Counted down");
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}
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}
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package com.baeldung.concurrent.countdownlatch;
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import java.util.List;
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import java.util.concurrent.CountDownLatch;
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public class Worker implements Runnable {
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private final List<String> outputScraper;
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private final CountDownLatch countDownLatch;
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public Worker(final List<String> outputScraper, final CountDownLatch countDownLatch) {
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this.outputScraper = outputScraper;
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this.countDownLatch = countDownLatch;
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}
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@Override
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public void run() {
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// Do some work
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System.out.println("Doing some logic");
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countDownLatch.countDown();
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outputScraper.add("Counted down");
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}
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}
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package com.baeldung.concurrent.countdownlatch;
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import org.assertj.core.api.Assertions;
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import org.junit.Test;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.List;
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import java.util.concurrent.CountDownLatch;
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import java.util.concurrent.TimeUnit;
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import java.util.concurrent.TimeoutException;
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import java.util.stream.Stream;
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import static java.util.stream.Collectors.toList;
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import static org.assertj.core.api.Assertions.assertThat;
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public class CountdownLatchExampleTest {
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@Test
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public void shouldBlockUntilLatchIsReleased() throws InterruptedException {
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// Given
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List<String> outputScraper = Collections.synchronizedList(new ArrayList<>());
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CountDownLatch countDownLatch = new CountDownLatch(5);
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List<Thread> workers = Stream
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.generate(() -> new Thread(new Worker(outputScraper, countDownLatch)))
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.limit(5)
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.collect(toList());
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// When
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workers.forEach(Thread::start);
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countDownLatch.await(); // Block until workers finish
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outputScraper.add("Latch released");
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// Then
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outputScraper.forEach(Object::toString);
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assertThat(outputScraper)
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.containsExactly(
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"Counted down",
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"Counted down",
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"Counted down",
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"Counted down",
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"Counted down",
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"Latch released"
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);
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}
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@Test
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public void shouldEventuallyTimeout() throws InterruptedException {
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// Given
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List<String> outputScraper = Collections.synchronizedList(new ArrayList<>());
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CountDownLatch countDownLatch = new CountDownLatch(5);
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List<Thread> workers = Stream
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.generate(() -> new Thread(new BrokenWorker(outputScraper, countDownLatch)))
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.limit(5)
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.collect(toList());
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// When
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workers.forEach(Thread::start);
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final boolean result = countDownLatch.await(3L, TimeUnit.SECONDS);
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// Then
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assertThat(result).isTrue();
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}
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}
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