Merge branch 'master' into BAEL-3442

core-java-modules/README.md

@@ -5,6 +5,5 @@ This module contains modules about core Java
 ## Relevant articles:
 
 - [Multi-Module Maven Application with Java Modules](https://www.baeldung.com/maven-multi-module-project-java-jpms)
-- [Guide to Java FileChannel](https://www.baeldung.com/java-filechannel)
 - [Understanding the NumberFormatException in Java](https://www.baeldung.com/java-number-format-exception)
 - [Will an Error Be Caught by Catch Block in Java?](https://www.baeldung.com/java-error-catch)

core-java-modules/core-java-10/pom.xml

@@ -1,7 +1,7 @@
+<?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">
+         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</groupId>
     <artifactId>core-java-10</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-10</name>

core-java-modules/core-java-11/README.md

@@ -12,4 +12,3 @@ This module contains articles about Java 11 core features
 - [An Introduction to Epsilon GC: A No-Op Experimental Garbage Collector](https://www.baeldung.com/jvm-epsilon-gc-garbage-collector)
 - [Guide to jlink](https://www.baeldung.com/jlink)
 - [Negate a Predicate Method Reference with Java 11](https://www.baeldung.com/java-negate-predicate-method-reference)
-- [Transforming an Empty String into an Empty Optional](https://www.baeldung.com/java-empty-string-to-empty-optional)

core-java-modules/core-java-11/pom.xml

@@ -1,9 +1,8 @@
-<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">
+<?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</groupId>
     <artifactId>core-java-11</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-11</name>
@@ -29,6 +28,27 @@
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh.version}</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.eclipse.collections</groupId>
+            <artifactId>eclipse-collections</artifactId>
+            <version>10.0.0</version>
+        </dependency>
+        <dependency>
+            <groupId>org.eclipse.collections</groupId>
+            <artifactId>eclipse-collections-api</artifactId>
+            <version>10.0.0</version>
+        </dependency>
     </dependencies>
 
     <build>
@@ -42,6 +62,42 @@
                     <target>${maven.compiler.target.version}</target>
                 </configuration>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-shade-plugin</artifactId>
+                <version>3.2.1</version>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>shade</goal>
+                        </goals>
+                        <configuration>
+                            <finalName>${uberjar.name}</finalName>
+                            <transformers>
+                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+                                    <mainClass>org.openjdk.jmh.Main</mainClass>
+                                </transformer>
+                                <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
+                            </transformers>
+                            <filters>
+                                <filter>
+                                    <!--
+                                        Shading signed JARs will fail without this.
+                                        http://stackoverflow.com/questions/999489/invalid-signature-file-when-attempting-to-run-a-jar
+                                    -->
+                                    <artifact>*:*</artifact>
+                                    <excludes>
+                                        <exclude>META-INF/*.SF</exclude>
+                                        <exclude>META-INF/*.DSA</exclude>
+                                        <exclude>META-INF/*.RSA</exclude>
+                                    </excludes>
+                                </filter>
+                            </filters>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
         </plugins>
     </build>
 
@@ -50,6 +106,8 @@
         <maven.compiler.target.version>11</maven.compiler.target.version>
         <guava.version>27.1-jre</guava.version>
         <assertj.version>3.11.1</assertj.version>
+        <uberjar.name>benchmarks</uberjar.name>
+        <jmh.version>1.22</jmh.version>
     </properties>
 
 </project>

core-java-modules/core-java-11/src/main/java/com/baeldung/benchmark/IntegerListFilter.java

@@ -0,0 +1,70 @@
+package com.baeldung.benchmark;
+
+import org.eclipse.collections.api.list.MutableList;
+import org.eclipse.collections.api.list.primitive.IntList;
+import org.eclipse.collections.api.list.primitive.MutableIntList;
+import org.eclipse.collections.impl.factory.primitive.IntLists;
+import org.eclipse.collections.impl.list.mutable.FastList;
+import org.eclipse.collections.impl.list.mutable.primitive.IntArrayList;
+import org.openjdk.jmh.annotations.*;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.PrimitiveIterator;
+import java.util.Random;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
+
+@State(Scope.Benchmark)
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.SECONDS)
+@Fork(2)
+public class IntegerListFilter {
+
+    private List<Integer> jdkIntList;
+    private MutableList<Integer> ecMutableList;
+    private IntList ecIntList;
+    private ExecutorService executor;
+
+    @Setup
+    public void setup() {
+        PrimitiveIterator.OfInt iterator = new Random(1L).ints(-10000, 10000).iterator();
+        ecMutableList = FastList.newWithNValues(1_000_000, iterator::nextInt);
+        jdkIntList = new ArrayList<>(1_000_000);
+        jdkIntList.addAll(ecMutableList);
+        ecIntList = ecMutableList.collectInt(i -> i, new IntArrayList(1_000_000));
+        executor = Executors.newWorkStealingPool();
+    }
+
+    @Benchmark
+    public List<Integer> jdkList() {
+        return jdkIntList.stream().filter(i -> i % 5 == 0).collect(Collectors.toList());
+    }
+
+    @Benchmark
+    public MutableList<Integer> ecMutableList() {
+        return ecMutableList.select(i -> i % 5 == 0);
+    }
+
+    @Benchmark
+    public List<Integer> jdkListParallel() {
+        return jdkIntList.parallelStream().filter(i -> i % 5 == 0).collect(Collectors.toList());
+    }
+
+    @Benchmark
+    public MutableList<Integer> ecMutableListParallel() {
+        return ecMutableList.asParallel(executor, 100_000).select(i -> i % 5 == 0).toList();
+    }
+
+    @Benchmark
+    public IntList ecPrimitive() {
+        return this.ecIntList.select(i -> i % 5 == 0);
+    }
+
+    @Benchmark
+    public IntList ecPrimitiveParallel() {
+        return this.ecIntList.primitiveParallelStream().filter(i -> i % 5 == 0).collect(IntLists.mutable::empty, MutableIntList::add, MutableIntList::addAll);
+    }
+}

core-java-modules/core-java-11/src/main/java/com/baeldung/benchmark/IntegerListSum.java

@@ -0,0 +1,67 @@
+package com.baeldung.benchmark;
+
+import org.eclipse.collections.api.list.MutableList;
+import org.eclipse.collections.api.list.primitive.IntList;
+import org.eclipse.collections.impl.list.mutable.FastList;
+import org.eclipse.collections.impl.list.mutable.primitive.IntArrayList;
+import org.openjdk.jmh.annotations.*;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.PrimitiveIterator;
+import java.util.Random;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+@State(Scope.Benchmark)
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.SECONDS)
+@Fork(2)
+public class IntegerListSum {
+
+    private List<Integer> jdkIntList;
+    private MutableList<Integer> ecMutableList;
+    private ExecutorService executor;
+    private IntList ecIntList;
+
+    @Setup
+    public void setup() {
+        PrimitiveIterator.OfInt iterator = new Random(1L).ints(-10000, 10000).iterator();
+        ecMutableList = FastList.newWithNValues(1_000_000, iterator::nextInt);
+        jdkIntList = new ArrayList<>(1_000_000);
+        jdkIntList.addAll(ecMutableList);
+        ecIntList = ecMutableList.collectInt(i -> i, new IntArrayList(1_000_000));
+        executor = Executors.newWorkStealingPool();
+    }
+
+    @Benchmark
+    public long jdkList() {
+        return jdkIntList.stream().mapToLong(i -> i).sum();
+    }
+
+    @Benchmark
+    public long ecMutableList() {
+        return ecMutableList.sumOfInt(i -> i);
+    }
+
+    @Benchmark
+    public long jdkListParallel() {
+        return jdkIntList.parallelStream().mapToLong(i -> i).sum();
+    }
+
+    @Benchmark
+    public long ecMutableListParallel() {
+        return ecMutableList.asParallel(executor, 100_000).sumOfInt(i -> i);
+    }
+
+    @Benchmark
+    public long ecPrimitive() {
+        return this.ecIntList.sum();
+    }
+
+    @Benchmark
+    public long ecPrimitiveParallel() {
+        return this.ecIntList.primitiveParallelStream().sum();
+    }
+}

core-java-modules/core-java-11/src/test/java/com/baeldung/benchmark/IntegerListFilterUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.benchmark;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+
+public class IntegerListFilterUnitTest {
+
+    private IntegerListFilter integerListFilter;
+
+    @Before
+    public void init() {
+        integerListFilter = new IntegerListFilter();
+        integerListFilter.setup();
+    }
+
+    @Test
+    public void whenBenchmarkIsExecute_thenJDKListsMustBeOfSameSize() {
+        assertEquals(integerListFilter.jdkList().size(), integerListFilter.jdkListParallel().size());
+    }
+
+    @Test
+    public void whenBenchmarkIsExecute_thenMutableListsMustBeOfSameSize() {
+        assertEquals(integerListFilter.ecMutableList().size(), integerListFilter.ecMutableListParallel().size());
+    }
+
+    @Test
+    public void whenBenchmarkIsExecute_thenPrimitiveListsMustBeOfSameSize() {
+        assertEquals(integerListFilter.ecPrimitive().size(), integerListFilter.ecPrimitiveParallel().size());
+    }
+}

core-java-modules/core-java-11/src/test/java/com/baeldung/benchmark/IntegerListSumUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.benchmark;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+
+public class IntegerListSumUnitTest {
+
+    private IntegerListSum integerListSum;
+
+    @Before
+    public void init() {
+        integerListSum = new IntegerListSum();
+        integerListSum.setup();
+    }
+
+    @Test
+    public void whenBenchmarkIsExecute_thenJDKListsMustHaveSameValue() {
+        assertEquals(integerListSum.jdkList(), integerListSum.jdkListParallel());
+    }
+
+    @Test
+    public void whenBenchmarkIsExecute_thenMutableListsMustHaveSameValue() {
+        assertEquals(integerListSum.ecMutableList(), integerListSum.ecMutableListParallel());
+    }
+
+    @Test
+    public void whenBenchmarkIsExecute_thenPrimitiveListsMustHaveSameValue() {
+        assertEquals(integerListSum.ecPrimitive(), integerListSum.ecPrimitiveParallel());
+    }
+}

core-java-modules/core-java-11/src/test/resources/sample.txt

@@ -0,0 +1 @@
+Sample file content

core-java-modules/core-java-12/pom.xml

@@ -1,9 +1,8 @@
 <?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">
+         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</groupId>
     <artifactId>core-java-12</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-12</name>

core-java-modules/core-java-13/pom.xml

@@ -0,0 +1,58 @@
+<?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</groupId>
+    <artifactId>core-java-13</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-13</name>
+    <packaging>jar</packaging>
+    <url>http://maven.apache.org</url>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source.version}</source>
+                    <target>${maven.compiler.target.version}</target>
+                    <release>13</release>
+                    <compilerArgs>--enable-preview</compilerArgs>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>3.0.0-M3</version>
+                <configuration>
+                    <argLine>--enable-preview</argLine>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <maven.compiler.source.version>13</maven.compiler.source.version>
+        <maven.compiler.target.version>13</maven.compiler.target.version>
+        <assertj.version>3.6.1</assertj.version>
+    </properties>
+
+</project>

core-java-modules/core-java-13/src/test/java/com/baeldung/switchExpression/SwitchExpressionsUnitTest.java

@@ -0,0 +1,76 @@
+package com.baeldung.switchExpression;
+
+import static java.time.Month.AUGUST;
+import static java.time.Month.JUNE;
+
+import static org.junit.Assert.assertEquals;
+
+import java.time.Month;
+import java.util.function.Function;
+
+import org.junit.Test;
+
+public class SwitchExpressionsUnitTest {
+
+  @Test
+  @SuppressWarnings ("preview")
+  public void whenSwitchingOverMonthJune_thenWillReturn3() {
+
+    var month = JUNE;
+
+    var result = switch (month) {
+      case JANUARY, JUNE, JULY -> 3;
+      case FEBRUARY, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER -> 1;
+      case MARCH, MAY, APRIL -> 2;
+      default -> 0;
+    };
+
+    assertEquals(result, 3);
+  }
+
+  @Test
+  @SuppressWarnings ("preview")
+  public void whenSwitchingOverMonthAugust_thenWillReturn24() {
+    var month = AUGUST;
+
+    var result = switch (month) {
+      case JANUARY, JUNE, JULY -> 3;
+      case FEBRUARY, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER -> 1;
+      case MARCH, MAY, APRIL, AUGUST -> {
+        int monthLength = month.toString().length();
+        yield monthLength * 4;
+      }
+      default -> 0;
+    };
+
+    assertEquals(24, result);
+  }
+
+  @Test
+  @SuppressWarnings ("preview")
+  public void whenSwitchingOverMonthJanuary_thenWillReturn3() {
+
+    Function<Month, Integer> func = (month) -> {
+      switch (month) {
+        case JANUARY, JUNE, JULY -> { return 3; }
+        default -> { return 0; }
+      }
+    };
+
+    assertEquals(Integer.valueOf(3), func.apply(Month.JANUARY));
+  }
+
+  @Test
+  @SuppressWarnings ("preview")
+  public void whenSwitchingOverMonthAugust_thenWillReturn2() {
+    var month = AUGUST;
+
+    var result = switch (month) {
+      case JANUARY, JUNE, JULY -> 3;
+      case FEBRUARY, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER -> 1;
+      case MARCH, MAY, APRIL, AUGUST -> 2;
+    };
+
+    assertEquals(result, 2);
+  }
+}

core-java-modules/core-java-8-2/README.md

@@ -3,9 +3,9 @@
 This module contains articles about Java 8 core features
 
 ### Relevant Articles: 
-- [Anonymous Classes in Java](http://www.baeldung.com/)
+- [Anonymous Classes in Java](https://www.baeldung.com/java-anonymous-classes)
 - [How to Delay Code Execution in Java](https://www.baeldung.com/java-delay-code-execution)
 - [Run a Java Application from the Command Line](https://www.baeldung.com/java-run-jar-with-arguments)
 - [Java 8 Stream skip() vs limit()](https://www.baeldung.com/java-stream-skip-vs-limit)
 - [Guide to Java BiFunction Interface](https://www.baeldung.com/java-bifunction-interface)
-- [[<-- Prev]](/core-java-modules/core-java-8)
+- [[<-- Prev]](/core-java-modules/core-java-8)

core-java-modules/core-java-8-2/pom.xml

@@ -1,7 +1,7 @@
 <?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">
+         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-8-2</artifactId>
     <version>0.1.0-SNAPSHOT</version>
@@ -33,4 +33,5 @@
         <icu.version>64.2</icu.version>
         <assertj.version>3.12.2</assertj.version>
     </properties>
+
 </project>

core-java-modules/core-java-8-2/src/main/resources/META-INF/persistence.xml

@@ -5,14 +5,14 @@
 	version="2.0">
 
 	<persistence-unit
-		name="com.baeldung.optionalReturnType"
+		name="com.baeldung.optionalreturntype"
 		transaction-type="RESOURCE_LOCAL">
 		<description>Persist Optional Return Type Demo</description>
 		<provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
-		<class>com.baeldung.optionalReturnType.User</class>
-		<class>com.baeldung.optionalReturnType.UserOptional</class>
+		<class>com.baeldung.optionalreturntype.User</class>
+		<class>com.baeldung.optionalreturntype.UserOptional</class>
 		<!-- 
-		<class>com.baeldung.optionalReturnType.UserOptionalField</class>
+		<class>com.baeldung.optionalreturntype.UserOptionalField</class>
 		-->
 		<exclude-unlisted-classes>true</exclude-unlisted-classes>
 

core-java-modules/core-java-8/pom.xml

@@ -1,3 +1,4 @@
+<?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>
@@ -76,4 +77,5 @@
         <!-- plugins -->
         <spring-boot-maven-plugin.version>2.0.4.RELEASE</spring-boot-maven-plugin.version>
     </properties>
+
 </project>

core-java-modules/core-java-8/src/main/java/com/baeldung/streamreduce/entities/Rating.java

@@ -0,0 +1,39 @@
+package com.baeldung.streamreduce.entities;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Rating {
+
+    double points;
+    List<Review> reviews = new ArrayList<>();
+
+    public Rating() {}
+
+    public void add(Review review) {
+        reviews.add(review);
+        computeRating();
+    }
+
+    private double computeRating() {
+        double totalPoints = reviews.stream().map(Review::getPoints).reduce(0, Integer::sum);
+        this.points = totalPoints / reviews.size();
+        return this.points;
+    }
+
+    public static Rating average(Rating r1, Rating r2) {
+        Rating combined = new Rating();
+        combined.reviews = new ArrayList<>(r1.reviews);
+        combined.reviews.addAll(r2.reviews);
+        combined.computeRating();
+        return combined;
+    }
+
+    public double getPoints() {
+        return points;
+    }
+
+    public List<Review> getReviews() {
+        return reviews;
+    }
+}

core-java-modules/core-java-8/src/main/java/com/baeldung/streamreduce/entities/Review.java

@@ -0,0 +1,28 @@
+package com.baeldung.streamreduce.entities;
+
+public class Review {
+
+    int points;
+    String review;
+
+    public Review(int points, String review) {
+        this.points = points;
+        this.review = review;
+    }
+
+    public int getPoints() {
+        return points;
+    }
+
+    public void setPoints(int points) {
+        this.points = points;
+    }
+
+    public String getReview() {
+        return review;
+    }
+
+    public void setReview(String review) {
+        this.review = review;
+    }
+}

core-java-modules/core-java-8/src/main/java/com/baeldung/streamreduce/entities/User.java

@@ -4,6 +4,7 @@ public class User {
 
     private final String name;
     private final int age;
+    private final Rating rating = new Rating();
 
     public User(String name, int age) {
         this.name = name;
@@ -17,7 +18,11 @@ public class User {
     public int getAge() {
         return age;
     }
-    
+
+    public Rating getRating() {
+        return rating;
+    }
+
     @Override
     public String toString() {
         return "User{" + "name=" + name + ", age=" + age + '}';

core-java-modules/core-java-8/src/test/java/com/baeldung/streamreduce/tests/StreamReduceManualTest.java

@@ -1,5 +1,7 @@
 package com.baeldung.streamreduce.tests;
 
+import com.baeldung.streamreduce.entities.Rating;
+import com.baeldung.streamreduce.entities.Review;
 import com.baeldung.streamreduce.entities.User;
 import com.baeldung.streamreduce.utilities.NumberUtils;
 import java.util.ArrayList;
@@ -64,6 +66,31 @@ public class StreamReduceManualTest {
         assertThat(result).isEqualTo(65);
     }
 
+    @Test
+    public void givenUserList_whenReduceWithGreaterAgeAccumulator_thenFindsOldest() {
+        List<User> users = Arrays.asList(new User("John", 30), new User("Alex", 40), new User("Julie", 35));
+
+        User oldest = users.stream().reduce(users.get(0), (user1, user2) -> user1.getAge() >= user2.getAge() ? user1 : user2);
+
+        assertThat(oldest).isEqualTo(users.get(1));
+    }
+
+    @Test
+    public void givenUserListWithRatings_whenReduceWithGreaterAgeAccumulator_thenFindsOldest() {
+        User john = new User("John", 30);
+        john.getRating().add(new Review(5, ""));
+        john.getRating().add(new Review(3, "not bad"));
+        User julie = new User("Julie", 35);
+        john.getRating().add(new Review(4, "great!"));
+        john.getRating().add(new Review(2, "terrible experience"));
+        john.getRating().add(new Review(4, ""));
+        List<User> users = Arrays.asList(john, julie);
+
+        Rating averageRating = users.stream().reduce(new Rating(), (rating, user) -> Rating.average(rating, user.getRating()), Rating::average);
+
+        assertThat(averageRating.getPoints()).isEqualTo(3.6);
+    }
+
     @Test
     public void givenStringList_whenReduceWithParallelStream_thenCorrect() {
         List<String> letters = Arrays.asList("a", "b", "c", "d", "e");

core-java-modules/core-java-9-improvements/README.md

@@ -0,0 +1,16 @@
+## Core Java 9
+
+This module contains articles about the improvements to core Java features introduced with Java 9.
+
+### Relevant Articles:
+
+- [New Stream Collectors in Java 9](http://www.baeldung.com/java9-stream-collectors)
+- [Java 9 Convenience Factory Methods for Collections](https://www.baeldung.com/java-9-collections-factory-methods)
+- [Java 9 Stream API Improvements](https://www.baeldung.com/java-9-stream-api)
+- [Java 9 java.util.Objects Additions](https://www.baeldung.com/java-9-objects-new)
+- [Java 9 CompletableFuture API Improvements](https://www.baeldung.com/java-9-completablefuture)
+
+#### Relevant articles not in this module:
+
+- [Java 9 Process API Improvements](https://www.baeldung.com/java-9-process-api) (see the [core-java-os](/core-java-os) module)
+

core-java-modules/core-java-9-improvements/pom.xml

@@ -0,0 +1,74 @@
+<?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-9-improvements</artifactId>
+    <version>0.2-SNAPSHOT</version>
+    <name>core-java-9-improvements</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.jayway.awaitility</groupId>
+            <artifactId>awaitility</artifactId>
+            <version>${awaitility.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-runner</artifactId>
+            <version>${junit.platform.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-9-improvements</finalName>
+        <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>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <pluginRepositories>
+        <pluginRepository>
+            <id>apache.snapshots</id>
+            <url>http://repository.apache.org/snapshots/</url>
+        </pluginRepository>
+    </pluginRepositories>
+
+    <properties>
+        <!-- testing -->
+        <assertj.version>3.10.0</assertj.version>
+        <junit.platform.version>1.2.0</junit.platform.version>
+        <awaitility.version>1.7.0</awaitility.version>
+        <maven.compiler.source>1.9</maven.compiler.source>
+        <maven.compiler.target>1.9</maven.compiler.target>
+        <guava.version>25.1-jre</guava.version>
+    </properties>
+
+</project>

core-java-modules/core-java-9-jigsaw/README.md

@@ -0,0 +1,11 @@
+## Core Java 9
+
+This module contains articles about Project Jigsaw and the Java Platform Module System (JPMS), introduced with Java 9.
+
+### Relevant Articles:
+
+- [Introduction to Project Jigsaw](http://www.baeldung.com/project-jigsaw-java-modularity)
+- [A Guide to Java 9 Modularity](https://www.baeldung.com/java-9-modularity)
+- [Java 9 java.lang.Module API](https://www.baeldung.com/java-9-module-api)
+
+

core-java-modules/core-java-9-jigsaw/pom.xml

@@ -0,0 +1,36 @@
+<?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-9-jigsaw</artifactId>
+    <version>0.2-SNAPSHOT</version>
+    <name>core-java-9-jigsaw</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <build>
+        <finalName>core-java-9-jigsaw</finalName>
+        <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>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <maven.compiler.source>1.9</maven.compiler.source>
+        <maven.compiler.target>1.9</maven.compiler.target>
+    </properties>
+
+</project>

core-java-modules/core-java-9-new-features/README.md

@@ -0,0 +1,14 @@
+## Core Java 9
+
+This module contains articles about core Java features that have been introduced in Java 9.
+
+### Relevant Articles:
+
+- [Java 9 New Features](https://www.baeldung.com/new-java-9)
+- [Java 9 Variable Handles Demystified](http://www.baeldung.com/java-variable-handles)
+- [Exploring the New HTTP Client in Java 9 and 11](http://www.baeldung.com/java-9-http-client)
+- [Multi-Release Jar Files](https://www.baeldung.com/java-multi-release-jar)
+- [Ahead of Time Compilation (AoT)](https://www.baeldung.com/ahead-of-time-compilation)
+- [Introduction to Java 9 StackWalking API](https://www.baeldung.com/java-9-stackwalking-api)
+- [Java 9 Platform Logging API](https://www.baeldung.com/java-9-logging-api)
+- [Java 9 Reactive Streams](https://www.baeldung.com/java-9-reactive-streams)

core-java-modules/core-java-9-new-features/pom.xml

@@ -0,0 +1,61 @@
+<?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-9-new-features</artifactId>
+    <version>0.2-SNAPSHOT</version>
+    <name>core-java-9-new-features</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-runner</artifactId>
+            <version>${junit.platform.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-9-new-features</finalName>
+        <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>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <pluginRepositories>
+        <pluginRepository>
+            <id>apache.snapshots</id>
+            <url>http://repository.apache.org/snapshots/</url>
+        </pluginRepository>
+    </pluginRepositories>
+
+    <properties>
+        <!-- testing -->
+        <assertj.version>3.10.0</assertj.version>
+        <junit.platform.version>1.2.0</junit.platform.version>
+        <maven.compiler.source>1.9</maven.compiler.source>
+        <maven.compiler.target>1.9</maven.compiler.target>
+    </properties>
+
+</project>

core-java-modules/core-java-9-streams/README.md

@@ -0,0 +1,6 @@
+## 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)

core-java-modules/core-java-9-streams/pom.xml

@@ -0,0 +1,27 @@
+<?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-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>
+
+    <build>
+        <finalName>core-java-9-streams</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+</project>

core-java-modules/core-java-9-streams/src/main/java/com/baeldung/streams/breakforeach/CustomForEach.java

@@ -0,0 +1,32 @@
+package com.baeldung.streams.breakforeach;
+
+import java.util.Spliterator;
+import java.util.function.BiConsumer;
+import java.util.stream.Stream;
+
+public class CustomForEach {
+
+    public static class Breaker {
+        private boolean shouldBreak = false;
+
+        public void stop() {
+            shouldBreak = true;
+        }
+
+        boolean get() {
+            return shouldBreak;
+        }
+    }
+
+    public static <T> void forEach(Stream<T> stream, BiConsumer<T, Breaker> consumer) {
+        Spliterator<T> spliterator = stream.spliterator();
+        boolean hadNext = true;
+        Breaker breaker = new Breaker();
+
+        while (hadNext && !breaker.get()) {
+            hadNext = spliterator.tryAdvance(elem -> {
+                consumer.accept(elem, breaker);
+            });
+        }
+    }
+}

core-java-modules/core-java-9-streams/src/main/java/com/baeldung/streams/breakforeach/CustomSpliterator.java

@@ -0,0 +1,31 @@
+package com.baeldung.streams.breakforeach;
+
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
+
+public class CustomSpliterator<T> extends Spliterators.AbstractSpliterator<T> {
+
+    private Spliterator<T> splitr;
+    private Predicate<T> predicate;
+    private boolean isMatched = true;
+
+    public CustomSpliterator(Spliterator<T> splitr, Predicate<T> predicate) {
+        super(splitr.estimateSize(), 0);
+        this.splitr = splitr;
+        this.predicate = predicate;
+    }
+
+    @Override
+    public boolean tryAdvance(Consumer<? super T> consumer) {
+        boolean hadNext = splitr.tryAdvance(elem -> {
+            if (predicate.test(elem) && isMatched) {
+                consumer.accept(elem);
+            } else {
+                isMatched = false;
+            }
+        });
+        return hadNext && isMatched;
+    }
+}

core-java-modules/core-java-9-streams/src/main/java/com/baeldung/streams/breakforeach/CustomTakeWhile.java

@@ -0,0 +1,14 @@
+package com.baeldung.streams.breakforeach;
+
+import java.util.function.Predicate;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+public class CustomTakeWhile {
+
+    public static <T> Stream<T> takeWhile(Stream<T> stream, Predicate<T> predicate) {
+        CustomSpliterator<T> customSpliterator = new CustomSpliterator<>(stream.spliterator(), predicate);
+        return StreamSupport.stream(customSpliterator, false);
+    }
+
+}