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BAEL-4876: Parallel stream examples added

This commit is contained in:
Daniel Strmecki 2021-05-03 11:18:02 +02:00
parent 442e5c1a7f
commit d160a09b01
4 changed files with 74 additions and 0 deletions
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1
core-java-modules/core-java-streams-3/pom.xml
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@ -47,6 +47,7 @@
</build>
<properties>
<lombok.version>1.18.20</lombok.version>
<!-- testing -->
<assertj.version>3.6.1</assertj.version>
</properties>

14
core-java-modules/core-java-streams-3/src/main/java/com/baeldung/streams/parallel/ParallelStream.java Normal file
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@ -0,0 +1,14 @@
package com.baeldung.streams.parallel;
import java.util.List;
public class ParallelStream {
public static void main(String[] args) {
List<Integer> listOfNumbers = List.of(1, 2, 3, 4);
listOfNumbers.parallelStream().forEach(number ->
System.out.println(number + " " + Thread.currentThread().getName())
);
}
}

14
core-java-modules/core-java-streams-3/src/main/java/com/baeldung/streams/parallel/SequentialStream.java Normal file
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@ -0,0 +1,14 @@
package com.baeldung.streams.parallel;
import java.util.List;
public class SequentialStream {
public static void main(String[] args) {
List<Integer> listOfNumbers = List.of(1, 2, 3, 4);
listOfNumbers.stream().forEach(number ->
System.out.println(number + " " + Thread.currentThread().getName())
);
}
}

45
core-java-modules/core-java-streams-3/src/test/java/com/baeldung/streams/parallel/ForkJoinUnitTest.java Normal file
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@ -0,0 +1,45 @@
package com.baeldung.streams.parallel;
import org.junit.jupiter.api.Test;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import static org.assertj.core.api.Assertions.assertThat;
class ForkJoinUnitTest {
@Test
void givenSequentialStreamOfNumbers_whenReducingSumWithIdentityFive_thenResultIsCorrect() {
List<Integer> listOfNumbers = List.of(1, 2, 3, 4);
int sum = listOfNumbers.stream().reduce(5, Integer::sum);
assertThat(sum).isEqualTo(15);
}
@Test
void givenParallelStreamOfNumbers_whenReducingSumWithIdentityFive_thenResultIsNotCorrect() {
List<Integer> listOfNumbers = List.of(1, 2, 3, 4);
int sum = listOfNumbers.parallelStream().reduce(5, Integer::sum);
assertThat(sum).isNotEqualTo(15);
}
@Test
void givenParallelStreamOfNumbers_whenReducingSumWithIdentityZero_thenResultIsCorrect() {
List<Integer> listOfNumbers = List.of(1, 2, 3, 4);
int sum = listOfNumbers.parallelStream().reduce(0, Integer::sum) + 5;
assertThat(sum).isEqualTo(15);
}
@Test
public void givenParallelStreamOfNumbers_whenUsingCustomThreadPool_thenResultIsCorrect()
throws InterruptedException, ExecutionException {
List<Integer> listOfNumbers = List.of(1, 2, 3, 4);
ForkJoinPool customThreadPool = new ForkJoinPool(4);
int sum = customThreadPool.submit(
() -> listOfNumbers.parallelStream().reduce(0, Integer::sum)).get();
customThreadPool.shutdown();
assertThat(sum).isEqualTo(10);
}
}