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Split or move java-streams module

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catalin-burcea
2019-10-27 11:09:34 +02:00
parent 699cc1027e
commit 62089a7abb
67 changed files with 881 additions and 1046 deletions
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6
core-java-modules/core-java-9-streams/README.md Normal file
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## Core Java 9 streams
This module contains articles about Java 9 streams
### Relevant Articles:
- [How to Break from Java Stream forEach](https://www.baeldung.com/java-break-stream-foreach)

31
core-java-modules/core-java-9-streams/pom.xml Normal file
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<artifactId>core-java-9-streams</artifactId>
<version>0.1.0-SNAPSHOT</version>
<name>core-java-9-streams</name>
<packaging>jar</packaging>
<parent>
<groupId>com.baeldung</groupId>
<artifactId>parent-java</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../../parent-java</relativePath>
</parent>
<dependencies>
</dependencies>
<build>
<finalName>core-java-9-streams</finalName>
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
</resource>
</resources>
</build>
<properties>
</properties>
</project>

2
java-streams-2/src/main/java/com/baeldung/breakforeach/CustomForEach.java → core-java-modules/core-java-9-streams/src/main/java/com/baeldung/streams/breakforeach/CustomForEach.java
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@@ -1,4 +1,4 @@
package com.baeldung.breakforeach;
package com.baeldung.streams.breakforeach;
import java.util.Spliterator;
import java.util.function.BiConsumer;

2
java-streams-2/src/main/java/com/baeldung/breakforeach/CustomSpliterator.java → core-java-modules/core-java-9-streams/src/main/java/com/baeldung/streams/breakforeach/CustomSpliterator.java
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@@ -1,4 +1,4 @@
package com.baeldung.breakforeach;
package com.baeldung.streams.breakforeach;
import java.util.Spliterator;
import java.util.Spliterators;

2
java-streams-2/src/main/java/com/baeldung/breakforeach/CustomTakeWhile.java → core-java-modules/core-java-9-streams/src/main/java/com/baeldung/streams/breakforeach/CustomTakeWhile.java
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@@ -1,4 +1,4 @@
package com.baeldung.breakforeach;
package com.baeldung.streams.breakforeach;
import java.util.function.Predicate;
import java.util.stream.Stream;

2
java-streams-2/src/main/java/com/baeldung/breakforeach/TakeWhileExample.java → core-java-modules/core-java-9-streams/src/main/java/com/baeldung/streams/breakforeach/TakeWhileExample.java
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@@ -1,4 +1,4 @@
package com.baeldung.breakforeach;
package com.baeldung.streams.breakforeach;
import java.util.List;
import java.util.stream.Stream;

2
java-streams-2/src/test/java/com/baeldung/breakforeach/BreakFromStreamForEachUnitTest.java → core-java-modules/core-java-9-streams/src/test/java/com/baeldung/streams/breakforeach/BreakFromStreamForEachUnitTest.java
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@@ -1,4 +1,4 @@
package com.baeldung.breakforeach;
package com.baeldung.streams.breakforeach;
import org.junit.Test;

16
core-java-modules/core-java-streams-2/README.md Normal file
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## Core Java streams
This module contains articles about the Stream API in Java.
### Relevant Articles:
- [The Java 8 Stream API Tutorial](https://www.baeldung.com/java-8-streams)
- [Introduction to Java 8 Streams](https://www.baeldung.com/java-8-streams-introduction)
- [Java 8 Stream findFirst() vs. findAny()](https://www.baeldung.com/java-stream-findfirst-vs-findany)
- [Guide to Stream.reduce()](https://www.baeldung.com/java-stream-reduce)
- [Java IntStream Conversions](https://www.baeldung.com/java-intstream-convert)
- [Java 8 Streams peek() API](https://www.baeldung.com/java-streams-peek-api)
- [Working With Maps Using Streams](https://www.baeldung.com/java-maps-streams)
- [Collect a Java Stream to an Immutable Collection](https://www.baeldung.com/java-stream-immutable-collection)
- [How to Add a Single Element to a Stream](https://www.baeldung.com/java-stream-append-prepend)
- [Operating on and Removing an Item from Stream](https://www.baeldung.com/java-use-remove-item-stream)
- More articles: [[<-- prev>]](/../core-java-streams) [[next -->]](/../core-java-streams-3)

100
java-streams-2/pom.xml → core-java-modules/core-java-streams-2/pom.xml
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@@ -1,49 +1,53 @@
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.baeldung.javastreams2</groupId>
<artifactId>java-streams-2</artifactId>
<version>1.0</version>
<name>java-streams-2</name>
<packaging>jar</packaging>
<parent>
<groupId>com.baeldung</groupId>
<artifactId>parent-java</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../parent-java</relativePath>
</parent>
<dependencies>
<dependency>
<groupId>org.openjdk.jmh</groupId>
<artifactId>jmh-core</artifactId>
<version>${jmh-core.version}</version>
</dependency>
<dependency>
<groupId>org.openjdk.jmh</groupId>
<artifactId>jmh-generator-annprocess</artifactId>
<version>${jmh-generator.version}</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>${junit.version}</version>
<scope>test</scope>
<type>jar</type>
</dependency>
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>${assertj.version}</version>
<scope>test</scope>
</dependency>
</dependencies>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.9</maven.compiler.source>
<maven.compiler.target>1.9</maven.compiler.target>
<assertj.version>3.11.1</assertj.version>
</properties>
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<artifactId>core-java-streams-2</artifactId>
<version>1.0</version>
<name>core-java-streams-2</name>
<packaging>jar</packaging>
<parent>
<groupId>com.baeldung</groupId>
<artifactId>parent-java</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../../parent-java</relativePath>
</parent>
<dependencies>
<dependency>
<groupId>org.openjdk.jmh</groupId>
<artifactId>jmh-core</artifactId>
<version>${jmh-core.version}</version>
</dependency>
<dependency>
<groupId>org.openjdk.jmh</groupId>
<artifactId>jmh-generator-annprocess</artifactId>
<version>${jmh-generator.version}</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>${log4j.version}</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>${junit.version}</version>
<scope>test</scope>
<type>jar</type>
</dependency>
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>${assertj.version}</version>
<scope>test</scope>
</dependency>
</dependencies>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.9</maven.compiler.source>
<maven.compiler.target>1.9</maven.compiler.target>
<assertj.version>3.11.1</assertj.version>
</properties>
</project>

78
java-streams-2/src/main/java/com/baeldung/reduce/application/Application.java → core-java-modules/core-java-streams-2/src/main/java/com/baeldung/reduce/application/Application.java
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@@ -1,39 +1,39 @@
package com.baeldung.reduce.application;
import com.baeldung.reduce.entities.User;
import com.baeldung.reduce.utilities.NumberUtils;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class Application {
public static void main(String[] args) {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
int result1 = numbers.stream().reduce(0, (subtotal, element) -> subtotal + element);
System.out.println(result1);
int result2 = numbers.stream().reduce(0, Integer::sum);
System.out.println(result2);
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result3 = letters.stream().reduce("", (partialString, element) -> partialString + element);
System.out.println(result3);
String result4 = letters.stream().reduce("", String::concat);
System.out.println(result4);
String result5 = letters.stream().reduce("", (partialString, element) -> partialString.toUpperCase() + element.toUpperCase());
System.out.println(result5);
List<User> users = Arrays.asList(new User("John", 30), new User("Julie", 35));
int result6 = users.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
System.out.println(result6);
String result7 = letters.parallelStream().reduce("", String::concat);
System.out.println(result7);
int result8 = users.parallelStream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
System.out.println(result8);
}
}
package com.baeldung.reduce.application;
import com.baeldung.reduce.entities.User;
import com.baeldung.reduce.utilities.NumberUtils;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class Application {
public static void main(String[] args) {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
int result1 = numbers.stream().reduce(0, (subtotal, element) -> subtotal + element);
System.out.println(result1);
int result2 = numbers.stream().reduce(0, Integer::sum);
System.out.println(result2);
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result3 = letters.stream().reduce("", (partialString, element) -> partialString + element);
System.out.println(result3);
String result4 = letters.stream().reduce("", String::concat);
System.out.println(result4);
String result5 = letters.stream().reduce("", (partialString, element) -> partialString.toUpperCase() + element.toUpperCase());
System.out.println(result5);
List<User> users = Arrays.asList(new User("John", 30), new User("Julie", 35));
int result6 = users.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
System.out.println(result6);
String result7 = letters.parallelStream().reduce("", String::concat);
System.out.println(result7);
int result8 = users.parallelStream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
System.out.println(result8);
}
}

104
java-streams-2/src/main/java/com/baeldung/reduce/benchmarks/JMHStreamReduceBenchMark.java → core-java-modules/core-java-streams-2/src/main/java/com/baeldung/reduce/benchmarks/JMHStreamReduceBenchMark.java
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@@ -1,52 +1,52 @@
package com.baeldung.reduce.benchmarks;
import com.baeldung.reduce.entities.User;
import java.util.ArrayList;
import java.util.List;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.RunnerException;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;
@State(Scope.Thread)
@BenchmarkMode(Mode.AverageTime)
public class JMHStreamReduceBenchMark {
private final List<User> userList = createUsers();
public static void main(String[] args) throws RunnerException {
Options options = new OptionsBuilder()
.include(JMHStreamReduceBenchMark.class.getSimpleName()).threads(1)
.forks(1).shouldFailOnError(true).shouldDoGC(true)
.jvmArgs("-server").build();
new Runner(options).run();
}
private List<User> createUsers() {
List<User> users = new ArrayList<>();
for (int i = 0; i <= 1000000; i++) {
users.add(new User("John" + i, i));
}
return users;
}
@Benchmark
public Integer executeReduceOnParallelizedStream() {
return this.userList
.parallelStream()
.reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
}
@Benchmark
public Integer executeReduceOnSequentialStream() {
return this.userList
.stream()
.reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
}
}
package com.baeldung.reduce.benchmarks;
import com.baeldung.reduce.entities.User;
import java.util.ArrayList;
import java.util.List;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.RunnerException;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;
@State(Scope.Thread)
@BenchmarkMode(Mode.AverageTime)
public class JMHStreamReduceBenchMark {
private final List<User> userList = createUsers();
public static void main(String[] args) throws RunnerException {
Options options = new OptionsBuilder()
.include(JMHStreamReduceBenchMark.class.getSimpleName()).threads(1)
.forks(1).shouldFailOnError(true).shouldDoGC(true)
.jvmArgs("-server").build();
new Runner(options).run();
}
private List<User> createUsers() {
List<User> users = new ArrayList<>();
for (int i = 0; i <= 1000000; i++) {
users.add(new User("John" + i, i));
}
return users;
}
@Benchmark
public Integer executeReduceOnParallelizedStream() {
return this.userList
.parallelStream()
.reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
}
@Benchmark
public Integer executeReduceOnSequentialStream() {
return this.userList
.stream()
.reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
}
}

50
java-streams/src/main/java/com/baeldung/reduce/entities/User.java → core-java-modules/core-java-streams-2/src/main/java/com/baeldung/reduce/entities/User.java
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@@ -1,25 +1,25 @@
package com.baeldung.reduce.entities;
public class User {
private final String name;
private final int age;
public User(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
@Override
public String toString() {
return "User{" + "name=" + name + ", age=" + age + '}';
}
}
package com.baeldung.reduce.entities;
public class User {
private final String name;
private final int age;
public User(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
@Override
public String toString() {
return "User{" + "name=" + name + ", age=" + age + '}';
}
}

104
java-streams-2/src/main/java/com/baeldung/reduce/utilities/NumberUtils.java → core-java-modules/core-java-streams-2/src/main/java/com/baeldung/reduce/utilities/NumberUtils.java
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@@ -1,52 +1,52 @@
package com.baeldung.reduce.utilities;
import java.util.List;
import java.util.function.BiFunction;
import java.util.logging.Level;
import java.util.logging.Logger;
public abstract class NumberUtils {
private static final Logger LOGGER = Logger.getLogger(NumberUtils.class.getName());
public static int divideListElements(List<Integer> values, Integer divider) {
return values.stream()
.reduce(0, (a, b) -> {
try {
return a / divider + b / divider;
} catch (ArithmeticException e) {
LOGGER.log(Level.INFO, "Arithmetic Exception: Division by Zero");
}
return 0;
});
}
public static int divideListElementsWithExtractedTryCatchBlock(List<Integer> values, int divider) {
return values.stream().reduce(0, (a, b) -> divide(a, divider) + divide(b, divider));
}
public static int divideListElementsWithApplyFunctionMethod(List<Integer> values, int divider) {
BiFunction<Integer, Integer, Integer> division = (a, b) -> a / b;
return values.stream().reduce(0, (a, b) -> applyFunction(division, a, divider) + applyFunction(division, b, divider));
}
private static int divide(int value, int factor) {
int result = 0;
try {
result = value / factor;
} catch (ArithmeticException e) {
LOGGER.log(Level.INFO, "Arithmetic Exception: Division by Zero");
}
return result;
}
private static int applyFunction(BiFunction<Integer, Integer, Integer> function, int a, int b) {
try {
return function.apply(a, b);
}
catch(Exception e) {
LOGGER.log(Level.INFO, "Exception thrown!");
}
return 0;
}
}
package com.baeldung.reduce.utilities;
import java.util.List;
import java.util.function.BiFunction;
import java.util.logging.Level;
import java.util.logging.Logger;
public abstract class NumberUtils {
private static final Logger LOGGER = Logger.getLogger(NumberUtils.class.getName());
public static int divideListElements(List<Integer> values, Integer divider) {
return values.stream()
.reduce(0, (a, b) -> {
try {
return a / divider + b / divider;
} catch (ArithmeticException e) {
LOGGER.log(Level.INFO, "Arithmetic Exception: Division by Zero");
}
return 0;
});
}
public static int divideListElementsWithExtractedTryCatchBlock(List<Integer> values, int divider) {
return values.stream().reduce(0, (a, b) -> divide(a, divider) + divide(b, divider));
}
public static int divideListElementsWithApplyFunctionMethod(List<Integer> values, int divider) {
BiFunction<Integer, Integer, Integer> division = (a, b) -> a / b;
return values.stream().reduce(0, (a, b) -> applyFunction(division, a, divider) + applyFunction(division, b, divider));
}
private static int divide(int value, int factor) {
int result = 0;
try {
result = value / factor;
} catch (ArithmeticException e) {
LOGGER.log(Level.INFO, "Arithmetic Exception: Division by Zero");
}
return result;
}
private static int applyFunction(BiFunction<Integer, Integer, Integer> function, int a, int b) {
try {
return function.apply(a, b);
}
catch(Exception e) {
LOGGER.log(Level.INFO, "Exception thrown!");
}
return 0;
}
}

2
java-streams/src/test/java/com/baeldung/stream/mycollectors/MyImmutableListCollector.java → core-java-modules/core-java-streams-2/src/main/java/com/baeldung/streams/MyImmutableListCollector.java
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@@ -1,4 +1,4 @@
package com.baeldung.stream.mycollectors;
package com.baeldung.streams;
import java.util.ArrayList;
import java.util.Collections;

0
java-streams/src/main/resources/logback.xml → core-java-modules/core-java-streams-2/src/main/resources/logback.xml
View File

0
java-streams-2/src/test/java/com/baeldung/convert/intstreams/IntStreamsConversionsUnitTest.java → core-java-modules/core-java-streams-2/src/test/java/com/baeldung/convert/intstreams/IntStreamsConversionsUnitTest.java
View File

159
java-streams-2/src/test/java/com/baeldung/reduce/tests/StreamReduceUnitTest.java → core-java-modules/core-java-streams-2/src/test/java/com/baeldung/reduce/StreamReduceUnitTest.java
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@@ -1,79 +1,80 @@
package com.baeldung.reduce.tests;
import com.baeldung.reduce.entities.User;
import com.baeldung.reduce.utilities.NumberUtils;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import static org.assertj.core.api.Assertions.assertThat;
import org.junit.Test;
public class StreamReduceUnitTest {
@Test
public void givenIntegerList_whenReduceWithSumAccumulatorLambda_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
int result = numbers.stream().reduce(0, (subtotal, element) -> subtotal + element);
assertThat(result).isEqualTo(21);
}
@Test
public void givenIntegerList_whenReduceWithSumAccumulatorMethodReference_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
int result = numbers.stream().reduce(0, Integer::sum);
assertThat(result).isEqualTo(21);
}
@Test
public void givenStringList_whenReduceWithConcatenatorAccumulatorLambda_thenCorrect() {
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result = letters.stream().reduce("", (partialString, element) -> partialString + element);
assertThat(result).isEqualTo("abcde");
}
@Test
public void givenStringList_whenReduceWithConcatenatorAccumulatorMethodReference_thenCorrect() {
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result = letters.stream().reduce("", String::concat);
assertThat(result).isEqualTo("abcde");
}
@Test
public void givenStringList_whenReduceWithUppercaseConcatenatorAccumulator_thenCorrect() {
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result = letters.stream().reduce("", (partialString, element) -> partialString.toUpperCase() + element.toUpperCase());
assertThat(result).isEqualTo("ABCDE");
}
@Test
public void givenUserList_whenReduceWithAgeAccumulatorAndSumCombiner_thenCorrect() {
List<User> users = Arrays.asList(new User("John", 30), new User("Julie", 35));
int result = users.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
assertThat(result).isEqualTo(65);
}
@Test
public void givenStringList_whenReduceWithParallelStream_thenCorrect() {
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result = letters.parallelStream().reduce("", String::concat);
assertThat(result).isEqualTo("abcde");
}
@Test
public void givenNumberUtilsClass_whenCalledDivideListElements_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
assertThat(NumberUtils.divideListElements(numbers, 1)).isEqualTo(21);
}
@Test
public void givenNumberUtilsClass_whenCalledDivideListElementsWithExtractedTryCatchBlock_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
assertThat(NumberUtils.divideListElementsWithExtractedTryCatchBlock(numbers, 1)).isEqualTo(21);
}
@Test
public void givenStream_whneCalleddivideListElementsWithApplyFunctionMethod_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
assertThat(NumberUtils.divideListElementsWithApplyFunctionMethod(numbers, 1)).isEqualTo(21);
}
}
package com.baeldung.reduce;
import com.baeldung.reduce.entities.User;
import com.baeldung.reduce.utilities.NumberUtils;
import org.junit.Test;
import java.util.Arrays;
import java.util.List;
import static org.assertj.core.api.Assertions.assertThat;
public class StreamReduceUnitTest {
@Test
public void givenIntegerList_whenReduceWithSumAccumulatorLambda_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
int result = numbers.stream().reduce(0, (subtotal, element) -> subtotal + element);
assertThat(result).isEqualTo(21);
}
@Test
public void givenIntegerList_whenReduceWithSumAccumulatorMethodReference_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
int result = numbers.stream().reduce(0, Integer::sum);
assertThat(result).isEqualTo(21);
}
@Test
public void givenStringList_whenReduceWithConcatenatorAccumulatorLambda_thenCorrect() {
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result = letters.stream().reduce("", (partialString, element) -> partialString + element);
assertThat(result).isEqualTo("abcde");
}
@Test
public void givenStringList_whenReduceWithConcatenatorAccumulatorMethodReference_thenCorrect() {
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result = letters.stream().reduce("", String::concat);
assertThat(result).isEqualTo("abcde");
}
@Test
public void givenStringList_whenReduceWithUppercaseConcatenatorAccumulator_thenCorrect() {
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result = letters.stream().reduce("", (partialString, element) -> partialString.toUpperCase() + element.toUpperCase());
assertThat(result).isEqualTo("ABCDE");
}
@Test
public void givenUserList_whenReduceWithAgeAccumulatorAndSumCombiner_thenCorrect() {
List<User> users = Arrays.asList(new User("John", 30), new User("Julie", 35));
int result = users.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
assertThat(result).isEqualTo(65);
}
@Test
public void givenStringList_whenReduceWithParallelStream_thenCorrect() {
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result = letters.parallelStream().reduce("", String::concat);
assertThat(result).isEqualTo("abcde");
}
@Test
public void givenNumberUtilsClass_whenCalledDivideListElements_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
assertThat(NumberUtils.divideListElements(numbers, 1)).isEqualTo(21);
}
@Test
public void givenNumberUtilsClass_whenCalledDivideListElementsWithExtractedTryCatchBlock_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
assertThat(NumberUtils.divideListElementsWithExtractedTryCatchBlock(numbers, 1)).isEqualTo(21);
}
@Test
public void givenStream_whneCalleddivideListElementsWithApplyFunctionMethod_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
assertThat(NumberUtils.divideListElementsWithApplyFunctionMethod(numbers, 1)).isEqualTo(21);
}
}

2
java-streams/src/main/java/com/baeldung/java_8_features/Detail.java → core-java-modules/core-java-streams-2/src/test/java/com/baeldung/streams/Detail.java
View File

@@ -1,4 +1,4 @@
package com.baeldung.java_8_features;
package com.baeldung.streams;
import java.util.Arrays;
import java.util.List;

2
java-streams/src/test/java/com/baeldung/java8/streams/Java8FindAnyFindFirstUnitTest.java → core-java-modules/core-java-streams-2/src/test/java/com/baeldung/streams/Java8FindAnyFindFirstUnitTest.java
View File

@@ -1,4 +1,4 @@
package com.baeldung.java8.streams;
package com.baeldung.streams;
import org.junit.Test;

3
java-streams/src/test/java/com/baeldung/java8/streams/Java8StreamApiUnitTest.java → core-java-modules/core-java-streams-2/src/test/java/com/baeldung/streams/Java8StreamApiUnitTest.java
View File

@@ -1,6 +1,5 @@
package com.baeldung.java8.streams;
package com.baeldung.streams;
import com.baeldung.stream.Product;
import org.junit.Before;
import org.junit.Test;
import org.slf4j.Logger;

3
java-streams/src/test/java/com/baeldung/java8/Java8StreamsUnitTest.java → core-java-modules/core-java-streams-2/src/test/java/com/baeldung/streams/Java8StreamsUnitTest.java
View File

@@ -1,6 +1,5 @@
package com.baeldung.java8;
package com.baeldung.streams;
import com.baeldung.java_8_features.Detail;
import org.junit.Before;
import org.junit.Test;

8
java-streams/src/test/java/com/baeldung/stream/PeekUnitTest.java → core-java-modules/core-java-streams-2/src/test/java/com/baeldung/streams/PeekUnitTest.java
View File

@@ -1,13 +1,13 @@
package com.baeldung.stream;
package com.baeldung.streams;
import static org.assertj.core.api.Assertions.assertThat;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import java.io.StringWriter;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import static org.assertj.core.api.Assertions.assertThat;
public class PeekUnitTest {

2
java-streams/src/main/java/com/baeldung/stream/Product.java → core-java-modules/core-java-streams-2/src/test/java/com/baeldung/streams/Product.java
View File

@@ -1,4 +1,4 @@
package com.baeldung.stream;
package com.baeldung.streams;
import java.util.List;
import java.util.stream.Stream;

2
java-streams/src/test/java/com/baeldung/stream/StreamAddUnitTest.java → core-java-modules/core-java-streams-2/src/test/java/com/baeldung/streams/StreamAddUnitTest.java
View File

@@ -1,4 +1,4 @@
package com.baeldung.stream;
package com.baeldung.streams;
import org.junit.Test;

5
java-streams/src/test/java/com/baeldung/stream/StreamMapUnitTest.java → core-java-modules/core-java-streams-2/src/test/java/com/baeldung/streams/StreamMapUnitTest.java
View File

@@ -1,16 +1,13 @@
package com.baeldung.stream;
package com.baeldung.streams;
import org.junit.Before;
import org.junit.Test;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

20
java-streams/src/test/java/com/baeldung/stream/StreamToImmutableUnitTest.java → core-java-modules/core-java-streams-2/src/test/java/com/baeldung/streams/StreamToImmutableUnitTest.java
View File

@@ -1,20 +1,12 @@
package com.baeldung.stream;
import static java.util.stream.Collectors.collectingAndThen;
import static java.util.stream.Collectors.toList;
import static java.util.stream.Collectors.toSet;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.stream.IntStream;
package com.baeldung.streams;
import com.google.common.collect.ImmutableList;
import org.junit.Test;
import com.baeldung.stream.mycollectors.MyImmutableListCollector;
import com.google.common.collect.ImmutableList;
import java.util.*;
import java.util.stream.IntStream;
import static java.util.stream.Collectors.*;
public class StreamToImmutableUnitTest {

12
java-streams/src/test/java/com/baeldung/stream/StreamOperateAndRemoveUnitTest.java → core-java-modules/core-java-streams-2/src/test/java/com/baeldung/streams/removeitem/StreamOperateAndRemoveUnitTest.java
View File

@@ -1,9 +1,4 @@
package com.baeldung.stream;
import java.util.ArrayList;
import java.util.List;
import java.util.function.Predicate;
import java.util.stream.Collectors;
package com.baeldung.streams.removeitem;
import org.junit.Assert;
import org.junit.Before;
@@ -11,6 +6,11 @@ import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayList;
import java.util.List;
import java.util.function.Predicate;
import java.util.stream.Collectors;
public class StreamOperateAndRemoveUnitTest {
private List<Item> itemList;

11
core-java-modules/core-java-streams-3/README.md Normal file
View File

@@ -0,0 +1,11 @@
## Core Java streams
This module contains articles about the Stream API in Java.
### Relevant Articles:
- [The Difference Between map() and flatMap()](https://www.baeldung.com/java-difference-map-and-flatmap)
- [How to Use if/else Logic in Java 8 Streams](https://www.baeldung.com/java-8-streams-if-else-logic)
- [The Difference Between Collection.stream().forEach() and Collection.forEach()](https://www.baeldung.com/java-collection-stream-foreach)
- [Guide to Java 8’s Collectors](https://www.baeldung.com/java-8-collectors)
- [Primitive Type Streams in Java 8](https://www.baeldung.com/java-8-primitive-streams)
- More articles: [[<-- prev>]](/../core-java-streams-2)

53
core-java-modules/core-java-streams-3/pom.xml Normal file
View File

@@ -0,0 +1,53 @@
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<artifactId>core-java-streams-3</artifactId>
<version>0.1.0-SNAPSHOT</version>
<name>core-java-streams-3</name>
<packaging>jar</packaging>
<parent>
<groupId>com.baeldung</groupId>
<artifactId>parent-java</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../../parent-java</relativePath>
</parent>
<dependencies>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>${commons-lang3.version}</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>${lombok.version}</version>
<scope>provided</scope>
</dependency>
<!-- test scoped -->
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>${assertj.version}</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<finalName>core-java-streams-3</finalName>
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
</resource>
</resources>
</build>
<properties>
<!-- testing -->
<assertj.version>3.6.1</assertj.version>
<!-- plugins -->
<maven-surefire-plugin.version>2.22.1</maven-surefire-plugin.version>
</properties>
</project>

2
core-java-modules/core-java-streams/src/main/java/com/baeldung/forEach/ReverseList.java → core-java-modules/core-java-streams-3/src/main/java/com/baeldung/streams/forEach/ReverseList.java
View File

@@ -1,4 +1,4 @@
package com.baeldung.forEach;
package com.baeldung.streams.forEach;
import java.util.ArrayList;
import java.util.Arrays;

2
java-streams/src/main/java/com/baeldung/stream/PrimitiveStreams.java → core-java-modules/core-java-streams-3/src/main/java/com/baeldung/streams/primitivestreams/PrimitiveStreams.java
View File

@@ -1,4 +1,4 @@
package com.baeldung.stream;
package com.baeldung.streams.primitivestreams;
import java.util.Arrays;
import java.util.stream.IntStream;

13
core-java-modules/core-java-streams-3/src/main/resources/logback.xml Normal file
View File

@@ -0,0 +1,13 @@
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
</pattern>
</encoder>
</appender>
<root level="INFO">
<appender-ref ref="STDOUT" />
</root>
</configuration>

2
core-java-modules/core-java-streams/src/test/java/com/baeldung/collectors/Java8CollectorsUnitTest.java → core-java-modules/core-java-streams-3/src/test/java/com/baeldung/streams/collectors/Java8CollectorsUnitTest.java
View File

@@ -1,4 +1,4 @@
package com.baeldung.collectors;
package com.baeldung.streams.collectors;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;

2
core-java-modules/core-java-streams/src/test/java/com/baeldung/stream/conditional/StreamForEachIfElseUnitTest.java → core-java-modules/core-java-streams-3/src/test/java/com/baeldung/streams/conditional/StreamForEachIfElseUnitTest.java
View File

@@ -1,4 +1,4 @@
package com.baeldung.stream.conditional;
package com.baeldung.streams.conditional;
import java.util.Arrays;
import java.util.List;

8
java-streams/src/test/java/com/baeldung/stream/PrimitiveStreamsUnitTest.java → core-java-modules/core-java-streams-3/src/test/java/com/baeldung/streams/primitivestreams/PrimitiveStreamsUnitTest.java
View File

@@ -1,14 +1,14 @@
package com.baeldung.stream;
package com.baeldung.streams.primitivestreams;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import org.junit.Test;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;
import org.junit.Test;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
public class PrimitiveStreamsUnitTest {

0
java-streams/.gitignore → core-java-modules/core-java-streams/.gitignore vendored
View File

19
core-java-modules/core-java-streams/README.md
View File

@@ -1,9 +1,16 @@
=========
## Core Java streams
## Core Java 8 Cookbooks and Examples
This module contains articles about the Stream API in Java.
### Relevant Articles:
- [The Difference Between map() and flatMap()](https://www.baeldung.com/java-difference-map-and-flatmap)
- [How to Use if/else Logic in Java 8 Streams](https://www.baeldung.com/java-8-streams-if-else-logic)
- [The Difference Between Collection.stream().forEach() and Collection.forEach()](https://www.baeldung.com/java-collection-stream-foreach)
- [Guide to Java 8’s Collectors](https://www.baeldung.com/java-8-collectors)
- [Java 8 and Infinite Streams](https://www.baeldung.com/java-inifinite-streams)
- [How to Get the Last Element of a Stream in Java?](https://www.baeldung.com/java-stream-last-element)
- [“Stream has already been operated upon or closed” Exception in Java](https://www.baeldung.com/java-stream-operated-upon-or-closed-exception)
- [Iterable to Stream in Java](https://www.baeldung.com/java-iterable-to-stream)
- [How to Iterate Over a Stream With Indices](https://www.baeldung.com/java-stream-indices)
- [Stream Ordering in Java](https://www.baeldung.com/java-stream-ordering)
- [Introduction to Protonpack](https://www.baeldung.com/java-protonpack)
- [Java Stream Filter with Lambda Expression](https://www.baeldung.com/java-stream-filter-lambda)
- [Counting Matches on a Stream Filter](https://www.baeldung.com/java-stream-filter-count)
- [Summing Numbers with Java Streams](https://www.baeldung.com/java-stream-sum)
- More articles: [[next -->]](/../core-java-streams-2)

83
core-java-modules/core-java-streams/pom.xml
View File

@@ -14,6 +14,34 @@
</parent>
<dependencies>
<!-- https://mvnrepository.com/artifact/org.openjdk.jmh/jmh-core -->
<dependency>
<groupId>org.openjdk.jmh</groupId>
<artifactId>jmh-core</artifactId>
<version>${jmh-core.version}</version>
</dependency>
<dependency>
<groupId>org.openjdk.jmh</groupId>
<artifactId>jmh-generator-annprocess</artifactId>
<version>${jmh-generator.version}</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>${commons-lang3.version}</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>${log4j.version}</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>${lombok.version}</version>
<scope>provided</scope>
</dependency>
<!-- test scoped -->
<dependency>
<groupId>org.assertj</groupId>
@@ -21,6 +49,36 @@
<version>${assertj.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.codepoetics</groupId>
<artifactId>protonpack</artifactId>
<version>${protonpack.version}</version>
</dependency>
<dependency>
<groupId>io.vavr</groupId>
<artifactId>vavr</artifactId>
<version>${vavr.version}</version>
</dependency>
<dependency>
<groupId>one.util</groupId>
<artifactId>streamex</artifactId>
<version>${streamex.version}</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>${asspectj.version}</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>${asspectj.version}</version>
</dependency>
<dependency>
<groupId>pl.touk</groupId>
<artifactId>throwing-function</artifactId>
<version>${throwing-function.version}</version>
</dependency>
</dependencies>
<build>
@@ -31,10 +89,33 @@
<filtering>true</filtering>
</resource>
</resources>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>${maven-compiler-plugin.version}</version>
<configuration>
<source>${maven.compiler.source}</source>
<target>${maven.compiler.target}</target>
<compilerArgument>-parameters</compilerArgument>
</configuration>
</plugin>
</plugins>
</build>
<properties>
<!-- util -->
<vavr.version>0.9.0</vavr.version>
<protonpack.version>1.15</protonpack.version>
<streamex.version>0.6.5</streamex.version>
<joda.version>2.10</joda.version>
<throwing-function.version>1.3</throwing-function.version>
<!-- testing -->
<assertj.version>3.6.1</assertj.version>
<assertj.version>3.11.1</assertj.version>
<asspectj.version>1.8.9</asspectj.version>
<maven-compiler-plugin.version>3.1</maven-compiler-plugin.version>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
</project>

0
java-streams/src/main/java/com/baeldung/stream/InfiniteStreams.java → core-java-modules/core-java-streams/src/main/java/com/baeldung/stream/InfiniteStreams.java
View File

0
java-streams/src/main/java/com/baeldung/stream/StreamApi.java → core-java-modules/core-java-streams/src/main/java/com/baeldung/stream/StreamApi.java
View File

0
java-streams/src/main/java/com/baeldung/stream/StreamIndices.java → core-java-modules/core-java-streams/src/main/java/com/baeldung/stream/StreamIndices.java
View File

0
java-streams/src/main/java/com/baeldung/stream/filter/Customer.java → core-java-modules/core-java-streams/src/main/java/com/baeldung/stream/filter/Customer.java
View File

16
java-streams/src/main/java/com/baeldung/stream/sum/ArithmeticUtils.java → core-java-modules/core-java-streams/src/main/java/com/baeldung/stream/sum/ArithmeticUtils.java
View File

@@ -1,8 +1,8 @@
package com.baeldung.stream.sum;
public class ArithmeticUtils {
public static int add(int a, int b) {
return a + b;
}
}
package com.baeldung.stream.sum;
public class ArithmeticUtils {
public static int add(int a, int b) {
return a + b;
}
}

62
java-streams/src/main/java/com/baeldung/stream/sum/Item.java → core-java-modules/core-java-streams/src/main/java/com/baeldung/stream/sum/Item.java
View File

@@ -1,31 +1,31 @@
package com.baeldung.stream.sum;
public class Item {
private int id;
private Integer price;
public Item(int id, Integer price) {
super();
this.id = id;
this.price = price;
}
// Standard getters and setters
public long getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public Integer getPrice() {
return price;
}
public void setPrice(Integer price) {
this.price = price;
}
}
package com.baeldung.stream.sum;
public class Item {
private int id;
private Integer price;
public Item(int id, Integer price) {
super();
this.id = id;
this.price = price;
}
// Standard getters and setters
public long getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public Integer getPrice() {
return price;
}
public void setPrice(Integer price) {
this.price = price;
}
}

118
java-streams/src/main/java/com/baeldung/stream/sum/StreamSumCalculator.java → core-java-modules/core-java-streams/src/main/java/com/baeldung/stream/sum/StreamSumCalculator.java
View File

@@ -1,59 +1,59 @@
package com.baeldung.stream.sum;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
public class StreamSumCalculator {
public static Integer getSumUsingCustomizedAccumulator(List<Integer> integers) {
return integers.stream()
.reduce(0, ArithmeticUtils::add);
}
public static Integer getSumUsingJavaAccumulator(List<Integer> integers) {
return integers.stream()
.reduce(0, Integer::sum);
}
public static Integer getSumUsingReduce(List<Integer> integers) {
return integers.stream()
.reduce(0, (a, b) -> a + b);
}
public static Integer getSumUsingCollect(List<Integer> integers) {
return integers.stream()
.collect(Collectors.summingInt(Integer::intValue));
}
public static Integer getSumUsingSum(List<Integer> integers) {
return integers.stream()
.mapToInt(Integer::intValue)
.sum();
}
public static Integer getSumOfMapValues(Map<Object, Integer> map) {
return map.values()
.stream()
.mapToInt(Integer::valueOf)
.sum();
}
public static Integer getSumIntegersFromString(String str) {
Integer sum = Arrays.stream(str.split(" "))
.filter((s) -> s.matches("\\d+"))
.mapToInt(Integer::valueOf)
.sum();
return sum;
}
}
package com.baeldung.stream.sum;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
public class StreamSumCalculator {
public static Integer getSumUsingCustomizedAccumulator(List<Integer> integers) {
return integers.stream()
.reduce(0, ArithmeticUtils::add);
}
public static Integer getSumUsingJavaAccumulator(List<Integer> integers) {
return integers.stream()
.reduce(0, Integer::sum);
}
public static Integer getSumUsingReduce(List<Integer> integers) {
return integers.stream()
.reduce(0, (a, b) -> a + b);
}
public static Integer getSumUsingCollect(List<Integer> integers) {
return integers.stream()
.collect(Collectors.summingInt(Integer::intValue));
}
public static Integer getSumUsingSum(List<Integer> integers) {
return integers.stream()
.mapToInt(Integer::intValue)
.sum();
}
public static Integer getSumOfMapValues(Map<Object, Integer> map) {
return map.values()
.stream()
.mapToInt(Integer::valueOf)
.sum();
}
public static Integer getSumIntegersFromString(String str) {
Integer sum = Arrays.stream(str.split(" "))
.filter((s) -> s.matches("\\d+"))
.mapToInt(Integer::valueOf)
.sum();
return sum;
}
}

76
java-streams/src/main/java/com/baeldung/stream/sum/StreamSumCalculatorWithObject.java → core-java-modules/core-java-streams/src/main/java/com/baeldung/stream/sum/StreamSumCalculatorWithObject.java
View File

@@ -1,38 +1,38 @@
package com.baeldung.stream.sum;
import java.util.List;
import java.util.stream.Collectors;
public class StreamSumCalculatorWithObject {
public static Integer getSumUsingCustomizedAccumulator(List<Item> items) {
return items.stream()
.map(x -> x.getPrice())
.reduce(0, ArithmeticUtils::add);
}
public static Integer getSumUsingJavaAccumulator(List<Item> items) {
return items.stream()
.map(x -> x.getPrice())
.reduce(0, Integer::sum);
}
public static Integer getSumUsingReduce(List<Item> items) {
return items.stream()
.map(item -> item.getPrice())
.reduce(0, (a, b) -> a + b);
}
public static Integer getSumUsingCollect(List<Item> items) {
return items.stream()
.map(x -> x.getPrice())
.collect(Collectors.summingInt(Integer::intValue));
}
public static Integer getSumUsingSum(List<Item> items) {
return items.stream()
.mapToInt(x -> x.getPrice())
.sum();
}
}
package com.baeldung.stream.sum;
import java.util.List;
import java.util.stream.Collectors;
public class StreamSumCalculatorWithObject {
public static Integer getSumUsingCustomizedAccumulator(List<Item> items) {
return items.stream()
.map(x -> x.getPrice())
.reduce(0, ArithmeticUtils::add);
}
public static Integer getSumUsingJavaAccumulator(List<Item> items) {
return items.stream()
.map(x -> x.getPrice())
.reduce(0, Integer::sum);
}
public static Integer getSumUsingReduce(List<Item> items) {
return items.stream()
.map(item -> item.getPrice())
.reduce(0, (a, b) -> a + b);
}
public static Integer getSumUsingCollect(List<Item> items) {
return items.stream()
.map(x -> x.getPrice())
.collect(Collectors.summingInt(Integer::intValue));
}
public static Integer getSumUsingSum(List<Item> items) {
return items.stream()
.mapToInt(x -> x.getPrice())
.sum();
}
}

2
java-streams/src/test/java/com/baeldung/java/conversion/IterableStreamConversionUnitTest.java → core-java-modules/core-java-streams/src/test/java/com/baeldung/conversion/IterableStreamConversionUnitTest.java
View File

@@ -1,4 +1,4 @@
package com.baeldung.java.conversion;
package com.baeldung.conversion;
import org.junit.Assert;
import org.junit.Test;

0
java-streams/src/test/java/com/baeldung/protonpack/ProtonpackUnitTest.java → core-java-modules/core-java-streams/src/test/java/com/baeldung/protonpack/ProtonpackUnitTest.java
View File

0
java-streams/src/test/java/com/baeldung/stream/InfiniteStreamUnitTest.java → core-java-modules/core-java-streams/src/test/java/com/baeldung/stream/InfiniteStreamUnitTest.java
View File

0
java-streams/src/test/java/com/baeldung/stream/StreamApiUnitTest.java → core-java-modules/core-java-streams/src/test/java/com/baeldung/stream/StreamApiUnitTest.java
View File

0
java-streams/src/test/java/com/baeldung/stream/StreamIndicesUnitTest.java → core-java-modules/core-java-streams/src/test/java/com/baeldung/stream/StreamIndicesUnitTest.java
View File

68
java-streams/src/test/java/com/baeldung/stream/SupplierStreamUnitTest.java → core-java-modules/core-java-streams/src/test/java/com/baeldung/stream/SupplierStreamUnitTest.java
View File

@@ -1,35 +1,35 @@
package com.baeldung.stream;
import static org.junit.Assert.fail;
import java.util.Optional;
import java.util.function.Supplier;
import java.util.stream.Stream;
import org.junit.Test;
public class SupplierStreamUnitTest {
@Test(expected = IllegalStateException.class)
public void givenStream_whenStreamUsedTwice_thenThrowException() {
Stream<String> stringStream = Stream.of("A", "B", "C", "D");
Optional<String> result1 = stringStream.findAny();
System.out.println(result1.get());
Optional<String> result2 = stringStream.findFirst();
System.out.println(result2.get());
}
@Test
public void givenStream_whenUsingSupplier_thenNoExceptionIsThrown() {
try {
Supplier<Stream<String>> streamSupplier = () -> Stream.of("A", "B", "C", "D");
Optional<String> result1 = streamSupplier.get().findAny();
System.out.println(result1.get());
Optional<String> result2 = streamSupplier.get().findFirst();
System.out.println(result2.get());
} catch (IllegalStateException e) {
fail();
}
}
package com.baeldung.stream;
import static org.junit.Assert.fail;
import java.util.Optional;
import java.util.function.Supplier;
import java.util.stream.Stream;
import org.junit.Test;
public class SupplierStreamUnitTest {
@Test(expected = IllegalStateException.class)
public void givenStream_whenStreamUsedTwice_thenThrowException() {
Stream<String> stringStream = Stream.of("A", "B", "C", "D");
Optional<String> result1 = stringStream.findAny();
System.out.println(result1.get());
Optional<String> result2 = stringStream.findFirst();
System.out.println(result2.get());
}
@Test
public void givenStream_whenUsingSupplier_thenNoExceptionIsThrown() {
try {
Supplier<Stream<String>> streamSupplier = () -> Stream.of("A", "B", "C", "D");
Optional<String> result1 = streamSupplier.get().findAny();
System.out.println(result1.get());
Optional<String> result2 = streamSupplier.get().findFirst();
System.out.println(result2.get());
} catch (IllegalStateException e) {
fail();
}
}
}

0
java-streams/src/test/java/com/baeldung/stream/filter/StreamCountUnitTest.java → core-java-modules/core-java-streams/src/test/java/com/baeldung/stream/filter/StreamCountUnitTest.java
View File

0
java-streams/src/test/java/com/baeldung/stream/filter/StreamFilterUnitTest.java → core-java-modules/core-java-streams/src/test/java/com/baeldung/stream/filter/StreamFilterUnitTest.java
View File

272
java-streams/src/test/java/com/baeldung/stream/sum/StreamSumUnitTest.java → core-java-modules/core-java-streams/src/test/java/com/baeldung/stream/sum/StreamSumUnitTest.java
View File

@@ -1,136 +1,136 @@
package com.baeldung.stream.sum;
import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.junit.jupiter.api.Test;
public class StreamSumUnitTest {
@Test
public void givenListOfIntegersWhenSummingUsingCustomizedAccumulatorThenCorrectValueReturned() {
List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
Integer sum = StreamSumCalculator.getSumUsingCustomizedAccumulator(integers);
assertEquals(15, sum.intValue());
}
@Test
public void givenListOfIntegersWhenSummingUsingJavaAccumulatorThenCorrectValueReturned() {
List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
Integer sum = StreamSumCalculator.getSumUsingJavaAccumulator(integers);
assertEquals(15, sum.intValue());
}
@Test
public void givenListOfIntegersWhenSummingUsingReduceThenCorrectValueReturned() {
List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
Integer sum = StreamSumCalculator.getSumUsingReduce(integers);
assertEquals(15, sum.intValue());
}
@Test
public void givenListOfIntegersWhenSummingUsingCollectThenCorrectValueReturned() {
List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
Integer sum = StreamSumCalculator.getSumUsingCollect(integers);
assertEquals(15, sum.intValue());
}
@Test
public void givenListOfIntegersWhenSummingUsingSumThenCorrectValueReturned() {
List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
Integer sum = StreamSumCalculator.getSumUsingSum(integers);
assertEquals(15, sum.intValue());
}
@Test
public void givenListOfItemsWhenSummingUsingCustomizedAccumulatorThenCorrectValueReturned() {
Item item1 = new Item(1, 10);
Item item2 = new Item(2, 15);
Item item3 = new Item(3, 25);
Item item4 = new Item(4, 40);
List<Item> items = Arrays.asList(item1, item2, item3, item4);
Integer sum = StreamSumCalculatorWithObject.getSumUsingCustomizedAccumulator(items);
assertEquals(90, sum.intValue());
}
@Test
public void givenListOfItemsWhenSummingUsingJavaAccumulatorThenCorrectValueReturned() {
Item item1 = new Item(1, 10);
Item item2 = new Item(2, 15);
Item item3 = new Item(3, 25);
Item item4 = new Item(4, 40);
List<Item> items = Arrays.asList(item1, item2, item3, item4);
Integer sum = StreamSumCalculatorWithObject.getSumUsingJavaAccumulator(items);
assertEquals(90, sum.intValue());
}
@Test
public void givenListOfItemsWhenSummingUsingReduceThenCorrectValueReturned() {
Item item1 = new Item(1, 10);
Item item2 = new Item(2, 15);
Item item3 = new Item(3, 25);
Item item4 = new Item(4, 40);
List<Item> items = Arrays.asList(item1, item2, item3, item4);
Integer sum = StreamSumCalculatorWithObject.getSumUsingReduce(items);
assertEquals(90, sum.intValue());
}
@Test
public void givenListOfItemsWhenSummingUsingCollectThenCorrectValueReturned() {
Item item1 = new Item(1, 10);
Item item2 = new Item(2, 15);
Item item3 = new Item(3, 25);
Item item4 = new Item(4, 40);
List<Item> items = Arrays.asList(item1, item2, item3, item4);
Integer sum = StreamSumCalculatorWithObject.getSumUsingCollect(items);
assertEquals(90, sum.intValue());
}
@Test
public void givenListOfItemsWhenSummingUsingSumThenCorrectValueReturned() {
Item item1 = new Item(1, 10);
Item item2 = new Item(2, 15);
Item item3 = new Item(3, 25);
Item item4 = new Item(4, 40);
List<Item> items = Arrays.asList(item1, item2, item3, item4);
Integer sum = StreamSumCalculatorWithObject.getSumUsingSum(items);
assertEquals(90, sum.intValue());
}
@Test
public void givenMapWhenSummingThenCorrectValueReturned() {
Map<Object, Integer> map = new HashMap<Object, Integer>();
map.put(1, 10);
map.put(2, 15);
map.put(3, 25);
map.put(4, 40);
Integer sum = StreamSumCalculator.getSumOfMapValues(map);
assertEquals(90, sum.intValue());
}
@Test
public void givenStringWhenSummingThenCorrectValueReturned() {
String string = "Item1 10 Item2 25 Item3 30 Item4 45";
Integer sum = StreamSumCalculator.getSumIntegersFromString(string);
assertEquals(110, sum.intValue());
}
}
package com.baeldung.stream.sum;
import static org.junit.jupiter.api.Assertions.assertEquals;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.junit.jupiter.api.Test;
public class StreamSumUnitTest {
@Test
public void givenListOfIntegersWhenSummingUsingCustomizedAccumulatorThenCorrectValueReturned() {
List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
Integer sum = StreamSumCalculator.getSumUsingCustomizedAccumulator(integers);
assertEquals(15, sum.intValue());
}
@Test
public void givenListOfIntegersWhenSummingUsingJavaAccumulatorThenCorrectValueReturned() {
List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
Integer sum = StreamSumCalculator.getSumUsingJavaAccumulator(integers);
assertEquals(15, sum.intValue());
}
@Test
public void givenListOfIntegersWhenSummingUsingReduceThenCorrectValueReturned() {
List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
Integer sum = StreamSumCalculator.getSumUsingReduce(integers);
assertEquals(15, sum.intValue());
}
@Test
public void givenListOfIntegersWhenSummingUsingCollectThenCorrectValueReturned() {
List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
Integer sum = StreamSumCalculator.getSumUsingCollect(integers);
assertEquals(15, sum.intValue());
}
@Test
public void givenListOfIntegersWhenSummingUsingSumThenCorrectValueReturned() {
List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5);
Integer sum = StreamSumCalculator.getSumUsingSum(integers);
assertEquals(15, sum.intValue());
}
@Test
public void givenListOfItemsWhenSummingUsingCustomizedAccumulatorThenCorrectValueReturned() {
Item item1 = new Item(1, 10);
Item item2 = new Item(2, 15);
Item item3 = new Item(3, 25);
Item item4 = new Item(4, 40);
List<Item> items = Arrays.asList(item1, item2, item3, item4);
Integer sum = StreamSumCalculatorWithObject.getSumUsingCustomizedAccumulator(items);
assertEquals(90, sum.intValue());
}
@Test
public void givenListOfItemsWhenSummingUsingJavaAccumulatorThenCorrectValueReturned() {
Item item1 = new Item(1, 10);
Item item2 = new Item(2, 15);
Item item3 = new Item(3, 25);
Item item4 = new Item(4, 40);
List<Item> items = Arrays.asList(item1, item2, item3, item4);
Integer sum = StreamSumCalculatorWithObject.getSumUsingJavaAccumulator(items);
assertEquals(90, sum.intValue());
}
@Test
public void givenListOfItemsWhenSummingUsingReduceThenCorrectValueReturned() {
Item item1 = new Item(1, 10);
Item item2 = new Item(2, 15);
Item item3 = new Item(3, 25);
Item item4 = new Item(4, 40);
List<Item> items = Arrays.asList(item1, item2, item3, item4);
Integer sum = StreamSumCalculatorWithObject.getSumUsingReduce(items);
assertEquals(90, sum.intValue());
}
@Test
public void givenListOfItemsWhenSummingUsingCollectThenCorrectValueReturned() {
Item item1 = new Item(1, 10);
Item item2 = new Item(2, 15);
Item item3 = new Item(3, 25);
Item item4 = new Item(4, 40);
List<Item> items = Arrays.asList(item1, item2, item3, item4);
Integer sum = StreamSumCalculatorWithObject.getSumUsingCollect(items);
assertEquals(90, sum.intValue());
}
@Test
public void givenListOfItemsWhenSummingUsingSumThenCorrectValueReturned() {
Item item1 = new Item(1, 10);
Item item2 = new Item(2, 15);
Item item3 = new Item(3, 25);
Item item4 = new Item(4, 40);
List<Item> items = Arrays.asList(item1, item2, item3, item4);
Integer sum = StreamSumCalculatorWithObject.getSumUsingSum(items);
assertEquals(90, sum.intValue());
}
@Test
public void givenMapWhenSummingThenCorrectValueReturned() {
Map<Object, Integer> map = new HashMap<Object, Integer>();
map.put(1, 10);
map.put(2, 15);
map.put(3, 25);
map.put(4, 40);
Integer sum = StreamSumCalculator.getSumOfMapValues(map);
assertEquals(90, sum.intValue());
}
@Test
public void givenStringWhenSummingThenCorrectValueReturned() {
String string = "Item1 10 Item2 25 Item3 30 Item4 45";
Integer sum = StreamSumCalculator.getSumIntegersFromString(string);
assertEquals(110, sum.intValue());
}
}

0
java-streams/src/test/java/com/baeldung/streamordering/BenchmarkManualTest.java → core-java-modules/core-java-streams/src/test/java/com/baeldung/streamordering/BenchmarkManualTest.java
View File

0
java-streams/src/test/java/com/baeldung/streamordering/StreamsOrderingUnitTest.java → core-java-modules/core-java-streams/src/test/java/com/baeldung/streamordering/StreamsOrderingUnitTest.java
View File

0
java-streams/src/test/resources/.gitignore → core-java-modules/core-java-streams/src/test/resources/.gitignore vendored
View File

2
core-java-modules/core-java/README.md
View File

@@ -7,7 +7,7 @@
- [How to Create an Executable JAR with Maven](http://www.baeldung.com/executable-jar-with-maven)
- [Introduction to Nashorn](http://www.baeldung.com/java-nashorn)
- [Java Money and the Currency API](http://www.baeldung.com/java-money-and-currency)
- [How to Add a Single Element to a Stream](http://www.baeldung.com/java-stream-append-prepend)
- [JVM Log Forging](http://www.baeldung.com/jvm-log-forging)
- [How to Find all Getters Returning Null](http://www.baeldung.com/java-getters-returning-null)
- [How to Get a Name of a Method Being Executed?](http://www.baeldung.com/java-name-of-executing-method)
- [Introduction to Java Serialization](http://www.baeldung.com/java-serialization)

9
java-streams-2/README.md
View File

@@ -1,9 +0,0 @@
## Java Streams Cookbooks and Examples
This module contains articles about the Stream API in Java.
### Relevant Articles:
- [Guide to Stream.reduce()](https://www.baeldung.com/java-stream-reduce)
- [How to Break from Java Stream forEach](https://www.baeldung.com/java-break-stream-foreach)
- [Java IntStream Conversions](https://www.baeldung.com/java-intstream-convert)
- More articles: [[<-- prev]](/java-streams)

25
java-streams-2/src/main/java/com/baeldung/reduce/entities/User.java
View File

@@ -1,25 +0,0 @@
package com.baeldung.reduce.entities;
public class User {
private final String name;
private final int age;
public User(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public int getAge() {
return age;
}
@Override
public String toString() {
return "User{" + "name=" + name + ", age=" + age + '}';
}
}

21
java-streams/README.md
View File

@@ -1,21 +0,0 @@
## Java Streams Cookbooks and Examples
This module contains articles about the Stream API in Java.
### Relevant Articles:
- [The Java 8 Stream API Tutorial](https://www.baeldung.com/java-8-streams)
- [Introduction to Java 8 Streams](https://www.baeldung.com/java-8-streams-introduction)
- [Java 8 and Infinite Streams](https://www.baeldung.com/java-inifinite-streams)
- [Java 8 Stream findFirst() vs. findAny()](https://www.baeldung.com/java-stream-findfirst-vs-findany)
- [How to Get the Last Element of a Stream in Java?](https://www.baeldung.com/java-stream-last-element)
- [“Stream has already been operated upon or closed” Exception in Java](https://www.baeldung.com/java-stream-operated-upon-or-closed-exception)
- [Iterable to Stream in Java](https://www.baeldung.com/java-iterable-to-stream)
- [How to Iterate Over a Stream With Indices](https://www.baeldung.com/java-stream-indices)
- [Primitive Type Streams in Java 8](https://www.baeldung.com/java-8-primitive-streams)
- [Stream Ordering in Java](https://www.baeldung.com/java-stream-ordering)
- [Introduction to Protonpack](https://www.baeldung.com/java-protonpack)
- [Java Stream Filter with Lambda Expression](https://www.baeldung.com/java-stream-filter-lambda)
- [Counting Matches on a Stream Filter](https://www.baeldung.com/java-stream-filter-count)
- [Java 8 Streams peek() API](https://www.baeldung.com/java-streams-peek-api)
- [Working With Maps Using Streams](https://www.baeldung.com/java-maps-streams)
- More articles: [[next -->]](/java-streams-2)

121
java-streams/pom.xml
View File

@@ -1,121 +0,0 @@
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<artifactId>java-streams</artifactId>
<version>0.1.0-SNAPSHOT</version>
<name>java-streams</name>
<packaging>jar</packaging>
<parent>
<groupId>com.baeldung</groupId>
<artifactId>parent-java</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../parent-java</relativePath>
</parent>
<dependencies>
<!-- https://mvnrepository.com/artifact/org.openjdk.jmh/jmh-core -->
<dependency>
<groupId>org.openjdk.jmh</groupId>
<artifactId>jmh-core</artifactId>
<version>${jmh-core.version}</version>
</dependency>
<dependency>
<groupId>org.openjdk.jmh</groupId>
<artifactId>jmh-generator-annprocess</artifactId>
<version>${jmh-generator.version}</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>${commons-lang3.version}</version>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>${log4j.version}</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>${lombok.version}</version>
<scope>provided</scope>
</dependency>
<!-- test scoped -->
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>${assertj.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.codepoetics</groupId>
<artifactId>protonpack</artifactId>
<version>${protonpack.version}</version>
</dependency>
<dependency>
<groupId>io.vavr</groupId>
<artifactId>vavr</artifactId>
<version>${vavr.version}</version>
</dependency>
<dependency>
<groupId>one.util</groupId>
<artifactId>streamex</artifactId>
<version>${streamex.version}</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>${asspectj.version}</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>${asspectj.version}</version>
</dependency>
<dependency>
<groupId>pl.touk</groupId>
<artifactId>throwing-function</artifactId>
<version>${throwing-function.version}</version>
</dependency>
</dependencies>
<build>
<finalName>java-streams</finalName>
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
</resource>
</resources>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>${maven-compiler-plugin.version}</version>
<configuration>
<source>${maven.compiler.source}</source>
<target>${maven.compiler.target}</target>
<compilerArgument>-parameters</compilerArgument>
</configuration>
</plugin>
</plugins>
</build>
<properties>
<!-- util -->
<vavr.version>0.9.0</vavr.version>
<protonpack.version>1.15</protonpack.version>
<streamex.version>0.6.5</streamex.version>
<joda.version>2.10</joda.version>
<throwing-function.version>1.3</throwing-function.version>
<!-- testing -->
<assertj.version>3.11.1</assertj.version>
<asspectj.version>1.8.9</asspectj.version>
<maven-compiler-plugin.version>3.1</maven-compiler-plugin.version>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
</project>

70
java-streams/src/main/java/com/baeldung/reduce/application/Application.java
View File

@@ -1,70 +0,0 @@
package com.baeldung.reduce.application;
import com.baeldung.reduce.entities.User;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.Warmup;
public class Application {
public static void main(String[] args) throws Exception {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
int result1 = numbers.stream().reduce(0, (subtotal, element) -> subtotal + element);
System.out.println(result1);
int result2 = numbers.stream().reduce(0, Integer::sum);
System.out.println(result2);
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result3 = letters.stream().reduce("", (partialString, element) -> partialString + element);
System.out.println(result3);
String result4 = letters.stream().reduce("", String::concat);
System.out.println(result4);
String result5 = letters.stream().reduce("", (partialString, element) -> partialString.toUpperCase() + element.toUpperCase());
System.out.println(result5);
List<User> users = Arrays.asList(new User("John", 30), new User("Julie", 35));
int result6 = users.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
System.out.println(result6);
String result7 = letters.parallelStream().reduce("", String::concat);
System.out.println(result7);
int result8 = users.parallelStream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
System.out.println(result8);
org.openjdk.jmh.Main.main(args);
}
@Benchmark
@Fork(value = 1, warmups = 2)
@Warmup(iterations = 2)
@BenchmarkMode(Mode.AverageTime)
public void executeReduceOnParallelizedStream() {
List<User> userList = new ArrayList<>();
for (int i = 0; i <= 1000000; i++) {
userList.add(new User("John" + i, i));
}
userList.parallelStream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
}
@Benchmark
@Fork(value = 1, warmups = 2)
@Warmup(iterations = 2)
@BenchmarkMode(Mode.AverageTime)
public void executeReduceOnSequentialStream() {
List<User> userList = new ArrayList<>();
for (int i = 0; i <= 1000000; i++) {
userList.add(new User("John" + i, i));
}
userList.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
}
}

52
java-streams/src/main/java/com/baeldung/reduce/utilities/NumberUtils.java
View File

@@ -1,52 +0,0 @@
package com.baeldung.reduce.utilities;
import java.util.List;
import java.util.function.BiFunction;
import java.util.logging.Level;
import java.util.logging.Logger;
public abstract class NumberUtils {
private static final Logger LOGGER = Logger.getLogger(NumberUtils.class.getName());
public static int divideListElements(List<Integer> values, Integer divider) {
return values.stream()
.reduce(0, (a, b) -> {
try {
return a / divider + b / divider;
} catch (ArithmeticException e) {
LOGGER.log(Level.INFO, "Arithmetic Exception: Division by Zero");
}
return 0;
});
}
public static int divideListElementsWithExtractedTryCatchBlock(List<Integer> values, int divider) {
return values.stream().reduce(0, (a, b) -> divide(a, divider) + divide(b, divider));
}
public static int divideListElementsWithApplyFunctionMethod(List<Integer> values, int divider) {
BiFunction<Integer, Integer, Integer> division = (a, b) -> a / b;
return values.stream().reduce(0, (a, b) -> applyFunction(division, a, divider) + applyFunction(division, b, divider));
}
private static int divide(int value, int factor) {
int result = 0;
try {
result = value / factor;
} catch (ArithmeticException e) {
LOGGER.log(Level.INFO, "Arithmetic Exception: Division by Zero");
}
return result;
}
private static int applyFunction(BiFunction<Integer, Integer, Integer> function, int a, int b) {
try {
return function.apply(a, b);
}
catch(Exception e) {
LOGGER.log(Level.INFO, "Exception occurred!");
}
return 0;
}
}

79
java-streams/src/test/java/com/baeldung/reduce/tests/StreamReduceUnitTest.java
View File

@@ -1,79 +0,0 @@
package com.baeldung.reduce.tests;
import com.baeldung.reduce.entities.User;
import com.baeldung.reduce.utilities.NumberUtils;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import static org.assertj.core.api.Assertions.assertThat;
import org.junit.Test;
public class StreamReduceUnitTest {
@Test
public void givenIntegerList_whenReduceWithSumAccumulatorLambda_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
int result = numbers.stream().reduce(0, (a, b) -> a + b);
assertThat(result).isEqualTo(21);
}
@Test
public void givenIntegerList_whenReduceWithSumAccumulatorMethodReference_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
int result = numbers.stream().reduce(0, Integer::sum);
assertThat(result).isEqualTo(21);
}
@Test
public void givenStringList_whenReduceWithConcatenatorAccumulatorLambda_thenCorrect() {
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result = letters.stream().reduce("", (a, b) -> a + b);
assertThat(result).isEqualTo("abcde");
}
@Test
public void givenStringList_whenReduceWithConcatenatorAccumulatorMethodReference_thenCorrect() {
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result = letters.stream().reduce("", String::concat);
assertThat(result).isEqualTo("abcde");
}
@Test
public void givenStringList_whenReduceWithUppercaseConcatenatorAccumulator_thenCorrect() {
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result = letters.stream().reduce("", (a, b) -> a.toUpperCase() + b.toUpperCase());
assertThat(result).isEqualTo("ABCDE");
}
@Test
public void givenUserList_whenReduceWithAgeAccumulatorAndSumCombiner_thenCorrect() {
List<User> users = Arrays.asList(new User("John", 30), new User("Julie", 35));
int result = users.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
assertThat(result).isEqualTo(65);
}
@Test
public void givenStringList_whenReduceWithParallelStream_thenCorrect() {
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
String result = letters.parallelStream().reduce("", String::concat);
assertThat(result).isEqualTo("abcde");
}
@Test
public void givenNumberUtilsClass_whenCalledDivideListElements_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
assertThat(NumberUtils.divideListElements(numbers, 1)).isEqualTo(21);
}
@Test
public void givenNumberUtilsClass_whenCalledDivideListElementsWithExtractedTryCatchBlock_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
assertThat(NumberUtils.divideListElementsWithExtractedTryCatchBlock(numbers, 1)).isEqualTo(21);
}
@Test
public void givenStream_whneCalleddivideListElementsWithApplyFunctionMethod_thenCorrect() {
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
assertThat(NumberUtils.divideListElementsWithApplyFunctionMethod(numbers, 1)).isEqualTo(21);
}
}

20
pom.xml
View File

@@ -381,7 +381,7 @@
<module>cloud-foundry-uaa/cf-uaa-oauth2-client</module>
<module>cloud-foundry-uaa/cf-uaa-oauth2-resource-server</module>
<module>code-generation</module>
<module>core-groovy</module>
<module>core-groovy</module>
<module>core-groovy-2</module>
<module>core-groovy-collections</module>
<!-- <module>core-java-modules/core-java-10</module> --> <!-- We haven't upgraded to java 10. Fixing in BAEL-10841 -->
@@ -391,6 +391,9 @@
<module>core-java-modules/core-java-8-2</module>
<module>core-java-modules/core-java-annotations</module>
<module>core-java-modules/core-java-streams</module>
<module>core-java-modules/core-java-streams-2</module>
<module>core-java-modules/core-java-streams-3</module>
<!-- <module>core-java-modules/core-java-9-streams</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
<module>core-java-modules/core-java-function</module>
<module>core-java-modules/core-java-lang-math</module>
<!-- We haven't upgraded to java 9.-->
@@ -500,8 +503,6 @@
<module>java-numbers-2</module>
<module>java-rmi</module>
<module>java-spi</module>
<module>java-streams</module>
<!-- <module>java-streams-2</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
<module>java-strings</module>
<module>java-strings-2</module>
<module>java-strings-3</module>
@@ -1152,7 +1153,7 @@
<module>cloud-foundry-uaa/cf-uaa-oauth2-client</module>
<module>cloud-foundry-uaa/cf-uaa-oauth2-resource-server</module>
<module>code-generation</module>
<module>core-groovy</module>
<module>core-groovy</module>
<module>core-groovy-2</module>
<module>core-groovy-collections</module>
<!-- <module>core-java-modules/core-java-10</module> --> <!-- We haven't upgraded to java 10. Fixing in BAEL-10841 -->
@@ -1161,6 +1162,9 @@
<module>core-java-modules/core-java-8-2</module>
<module>core-java-modules/core-java-annotations</module>
<module>core-java-modules/core-java-streams</module>
<module>core-java-modules/core-java-streams-2</module>
<module>core-java-modules/core-java-streams-3</module>
<!-- <module>core-java-modules/core-java-9-streams</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
<module>core-java-modules/core-java-function</module>
<module>core-java-modules/core-java-lang-math</module>
<!-- We haven't upgraded to java 9.-->
@@ -1204,9 +1208,9 @@
<module>core-java-modules/core-java-perf</module>
<module>core-java-modules/core-java-sun</module>
<module>core-java-modules/core-java-string-conversions</module>
<module>core-java-modules/core-java-string-conversions-2</module>
<module>core-java-modules/core-java-string-apis</module>
<module>core-scala</module>
<module>core-java-modules/core-java-string-conversions-2</module>
<module>core-java-modules/core-java-string-apis</module>
<module>core-scala</module>
<module>couchbase</module>
<module>custom-pmd</module>
@@ -1266,8 +1270,6 @@
<module>java-numbers-2</module>
<module>java-rmi</module>
<module>java-spi</module>
<module>java-streams</module>
<!-- <module>java-streams-2</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
<module>java-strings</module>
<module>java-strings-2</module>
<module>java-strings-3</module>