Merge branch 'master' of github.com:eugenp/tutorials

core-java-modules/README.md

@@ -1,6 +1,9 @@
+## Core Java Modules
+
+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/README.md

@@ -1,3 +1,6 @@
+## Core Java 10
+
+This module contains articles about Java 10 core features
 
 ### Relevant Articles: 
 

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

@@ -1,3 +1,7 @@
+## Core Java 11
+
+This module contains articles about Java 11 core features
+
 ### Relevant articles
 
 - [Java 11 Single File Source Code](https://www.baeldung.com/java-single-file-source-code)
@@ -8,4 +12,3 @@
 - [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-8-2/README.md

@@ -1,10 +1,11 @@
-=========
+## Core Java 8 (part 2)
 
-## Core Java 8 Cookbooks and Examples (part 2)
+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 JAR Application With Command Line Arguments](https://www.baeldung.com/java-run-jar-with-arguments)
+- [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)

core-java-modules/core-java-8-2/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-8-2</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-8-2</name>
@@ -30,25 +29,9 @@
         </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}</source>
-                    <target>${maven.compiler.target}</target>
-                </configuration>
-            </plugin>
-        </plugins>
-    </build>
-
     <properties>
-        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <maven.compiler.source>1.8</maven.compiler.source>
-        <maven.compiler.target>1.8</maven.compiler.target>
         <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/README.md

@@ -1,38 +1,15 @@
-=========
+## Core Java 8
 
-## Core Java 8 Cookbooks and Examples
+This module contains articles about Java 8 core features
 
 ### Relevant Articles: 
-- [Guide to Java 8’s Collectors](http://www.baeldung.com/java-8-collectors)
-- [New Features in Java 8](http://www.baeldung.com/java-8-new-features)
-- [The Double Colon Operator in Java 8](http://www.baeldung.com/java-8-double-colon-operator)
-- [Guide to Java 8 groupingBy Collector](http://www.baeldung.com/java-groupingby-collector)
-- [Strategy Design Pattern in Java 8](http://www.baeldung.com/java-strategy-pattern)
-- [Guide to Java 8 Comparator.comparing()](http://www.baeldung.com/java-8-comparator-comparing)
-- [Guide To Java 8 Optional](http://www.baeldung.com/java-optional)
-- [Guide to the Java 8 forEach](http://www.baeldung.com/foreach-java)
-- [The Difference Between map() and flatMap()](http://www.baeldung.com/java-difference-map-and-flatmap)
-- [Static and Default Methods in Interfaces in Java](http://www.baeldung.com/java-static-default-methods)
-- [Efficient Word Frequency Calculator in Java](http://www.baeldung.com/java-word-frequency)
-- [Introduction to Spliterator in Java](http://www.baeldung.com/java-spliterator)
-- [Java 8 Math New Methods](http://www.baeldung.com/java-8-math)
-- [Overview of Java Built-in Annotations](http://www.baeldung.com/java-default-annotations)
-- [Finding Min/Max in an Array with Java](http://www.baeldung.com/java-array-min-max)
-- [Internationalization and Localization in Java 8](http://www.baeldung.com/java-8-localization)
-- [Java Optional – orElse() vs orElseGet()](http://www.baeldung.com/java-optional-or-else-vs-or-else-get)
-- [Method Parameter Reflection in Java](http://www.baeldung.com/java-parameter-reflection)
-- [Java 8 Unsigned Arithmetic Support](http://www.baeldung.com/java-unsigned-arithmetic)
-- [Generalized Target-Type Inference in Java](http://www.baeldung.com/java-generalized-target-type-inference)
-- [Overriding System Time for Testing in Java](http://www.baeldung.com/java-override-system-time)
-- [Set the Time Zone of a Date in Java](https://www.baeldung.com/java-set-date-time-zone)
-- [An Overview of Regular Expressions Performance in Java](https://www.baeldung.com/java-regex-performance)
-- [Java Primitives versus Objects](https://www.baeldung.com/java-primitives-vs-objects)
-- [How to Use if/else Logic in Java 8 Streams](https://www.baeldung.com/java-8-streams-if-else-logic)
-- [How to Replace Many if Statements in Java](https://www.baeldung.com/java-replace-if-statements)
-- [Java @Override Annotation](https://www.baeldung.com/java-override)
-- [Java @SuppressWarnings Annotation](https://www.baeldung.com/java-suppresswarnings)
-- [Java @SafeVarargs Annotation](https://www.baeldung.com/java-safevarargs)
-- [Java @Deprecated Annotation](https://www.baeldung.com/java-deprecated)
-- [Java 8 Predicate Chain](https://www.baeldung.com/java-predicate-chain)
-- [Creating a Custom Annotation in Java](https://www.baeldung.com/java-custom-annotation)
-- [The Difference Between Collection.stream().forEach() and Collection.forEach()](https://www.baeldung.com/java-collection-stream-foreach)
+- [New Features in Java 8](https://www.baeldung.com/java-8-new-features)
+- [Guide to Java 8 groupingBy Collector](https://www.baeldung.com/java-groupingby-collector)
+- [Strategy Design Pattern in Java 8](https://www.baeldung.com/java-strategy-pattern)
+- [Guide to Java 8 Comparator.comparing()](https://www.baeldung.com/java-8-comparator-comparing)
+- [Guide to the Java 8 forEach](https://www.baeldung.com/foreach-java)
+- [Introduction to Spliterator in Java](https://www.baeldung.com/java-spliterator)
+- [Finding Min/Max in an Array with Java](https://www.baeldung.com/java-array-min-max)
+- [Internationalization and Localization in Java 8](https://www.baeldung.com/java-8-localization)
+- [Generalized Target-Type Inference in Java](https://www.baeldung.com/java-generalized-target-type-inference)
+- [[More -->]](/core-java-modules/core-java-8-2)

core-java-modules/core-java-8/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">
     <modelVersion>4.0.0</modelVersion>
-    <groupId>com.baeldung</groupId>
     <artifactId>core-java-8</artifactId>
     <version>0.1.0-SNAPSHOT</version>
     <name>core-java-8</name>
@@ -20,31 +20,11 @@
             <artifactId>commons-collections4</artifactId>
             <version>${commons-collections4.version}</version>
         </dependency>
-        <dependency>
-            <groupId>commons-io</groupId>
-            <artifactId>commons-io</artifactId>
-            <version>${commons-io.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.apache.commons</groupId>
-            <artifactId>commons-lang3</artifactId>
-            <version>${commons-lang3.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>org.apache.commons</groupId>
-            <artifactId>commons-math3</artifactId>
-            <version>${commons-math3.version}</version>
-        </dependency>
         <dependency>
             <groupId>log4j</groupId>
             <artifactId>log4j</artifactId>
             <version>${log4j.version}</version>
         </dependency>
-        <dependency>
-            <groupId>commons-codec</groupId>
-            <artifactId>commons-codec</artifactId>
-            <version>${commons-codec.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.projectlombok</groupId>
             <artifactId>lombok</artifactId>
@@ -58,70 +38,6 @@
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
-        <dependency>
-            <groupId>com.jayway.awaitility</groupId>
-            <artifactId>awaitility</artifactId>
-            <version>${avaitility.version}</version>
-            <scope>test</scope>
-        </dependency>
-        <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>org.openjdk.jmh</groupId>
-            <artifactId>jmh-generator-bytecode</artifactId>
-            <version>${jmh-generator.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.codepoetics</groupId>
-            <artifactId>protonpack</artifactId>
-            <version>${protonpack.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>io.vavr</groupId>
-            <artifactId>vavr</artifactId>
-            <version>${vavr.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>joda-time</groupId>
-            <artifactId>joda-time</artifactId>
-            <version>${joda.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>org.powermock</groupId>
-            <artifactId>powermock-module-junit4</artifactId>
-            <version>${powermock.version}</version>
-            <scope>test</scope>
-        </dependency>
-        <dependency>
-            <groupId>org.powermock</groupId>
-            <artifactId>powermock-api-mockito2</artifactId>
-            <version>${powermock.version}</version>
-            <scope>test</scope>
-        </dependency>
-        <dependency>
-            <groupId>org.jmockit</groupId>
-            <artifactId>jmockit</artifactId>
-            <version>${jmockit.version}</version>
-            <scope>test</scope>
-        </dependency>
     </dependencies>
 
     <build>
@@ -134,16 +50,6 @@
         </resources>
 
         <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-compiler-plugin</artifactId>
-                <version>${maven-compiler-plugin.version}</version>
-                <configuration>
-                    <source>1.8</source>
-                    <target>1.8</target>
-                    <compilerArgument>-parameters</compilerArgument>
-                </configuration>
-            </plugin>
             <plugin>
                 <groupId>org.springframework.boot</groupId>
                 <artifactId>spring-boot-maven-plugin</artifactId>
@@ -160,39 +66,16 @@
                     </execution>
                 </executions>
             </plugin>
-            <plugin>
-                <artifactId>maven-surefire-plugin</artifactId>
-                <version>${maven-surefire-plugin.version}</version>
-                <configuration>
-                    <argLine>
-                        -javaagent:${settings.localRepository}/org/jmockit/jmockit/${jmockit.version}/jmockit-${jmockit.version}.jar
-                    </argLine>
-                    <disableXmlReport>true</disableXmlReport>
-                </configuration>
-            </plugin>
         </plugins>
     </build>
 
     <properties>
         <!-- util -->
-        <commons-math3.version>3.6.1</commons-math3.version>
         <commons-collections4.version>4.1</commons-collections4.version>
-        <collections-generic.version>4.01</collections-generic.version>
-        <commons-codec.version>1.10</commons-codec.version>
-        <vavr.version>0.9.0</vavr.version>
-        <protonpack.version>1.13</protonpack.version>
-        <joda.version>2.10</joda.version>
         <!-- testing -->
         <assertj.version>3.6.1</assertj.version>
-        <asspectj.version>1.8.9</asspectj.version>
-        <powermock.version>2.0.0-RC.4</powermock.version>
-        <jmockit.version>1.44</jmockit.version>
-        <avaitility.version>1.7.0</avaitility.version>
-        <jmh-core.version>1.19</jmh-core.version>
-        <jmh-generator.version>1.19</jmh-generator.version>
-        <spring-boot-maven-plugin.version>2.0.4.RELEASE</spring-boot-maven-plugin.version>
         <!-- plugins -->
-        <maven-compiler-plugin.version>3.8.0</maven-compiler-plugin.version>
-        <maven-surefire-plugin.version>2.22.1</maven-surefire-plugin.version>
+        <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/java_8_features/groupingby/Tuple.java

@@ -1,12 +1,12 @@
 package com.baeldung.java_8_features.groupingby;
 
-public class Tuple {
+import java.util.Objects;
+
+public class Tuple {
+    private final BlogPostType type;
+    private final String author;
 
-    private BlogPostType type;
-    private String author;
-    
     public Tuple(BlogPostType type, String author) {
-        super();
         this.type = type;
         this.author = author;
     }
@@ -15,20 +15,27 @@ public class Tuple {
         return type;
     }
 
-    public void setType(BlogPostType type) {
-        this.type = type;
-    }
-
     public String getAuthor() {
         return author;
     }
 
-    public void setAuthor(String author) {
-        this.author = author;
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
+        Tuple tuple = (Tuple) o;
+        return type == tuple.type && author.equals(tuple.author);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(type, author);
     }
 
     @Override
     public String toString() {
-        return "Tuple [type=" + type + ", author=" + author + ", getType()=" + getType() + ", getAuthor()=" + getAuthor() + ", getClass()=" + getClass() + ", hashCode()=" + hashCode() + ", toString()=" + super.toString() + "]";
+        return "Tuple{" + "type=" + type + ", author='" + author + '\'' + '}';
     }
 }

core-java-modules/core-java-8/src/main/java/com/baeldung/optional/PersonRepository.java

@@ -1,9 +0,0 @@
-package com.baeldung.optional;
-
-public class PersonRepository {
-
-    public String findNameById(String id) {
-        return id == null ? null : "Name";
-    }
-
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/AddCommand.java

@@ -1,17 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public class AddCommand implements Command {
-
-    private int a;
-    private int b;
-
-    public AddCommand(int a, int b) {
-        this.a = a;
-        this.b = b;
-    }
-
-    @Override
-    public Integer execute() {
-        return a + b;
-    }
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/AddRule.java

@@ -1,21 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public class AddRule implements Rule {
-
-    private int result;
-
-    @Override
-    public boolean evaluate(Expression expression) {
-        boolean evalResult = false;
-        if (expression.getOperator() == Operator.ADD) {
-            this.result = expression.getX() + expression.getY();
-            evalResult = true;
-        }
-        return evalResult;
-    }
-
-    @Override
-    public Result getResult() {
-        return new Result(result);
-    }
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/Addition.java

@@ -1,8 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public class Addition implements Operation {
-    @Override
-    public int apply(int a, int b) {
-        return a + b;
-    }
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/Calculator.java

@@ -1,83 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public class Calculator {
-
-    public int calculate(int a, int b, String operator) {
-        int result = Integer.MIN_VALUE;
-
-        if ("add".equals(operator)) {
-            result = a + b;
-        } else if ("multiply".equals(operator)) {
-            result = a * b;
-        } else if ("divide".equals(operator)) {
-            result = a / b;
-        } else if ("subtract".equals(operator)) {
-            result = a - b;
-        } else if ("modulo".equals(operator)) {
-            result = a % b;
-        }
-        return result;
-    }
-
-    public int calculateUsingSwitch(int a, int b, String operator) {
-        int result = 0;
-        switch (operator) {
-        case "add":
-            result = a + b;
-            break;
-        case "multiply":
-            result = a * b;
-            break;
-        case "divide":
-            result = a / b;
-            break;
-        case "subtract":
-            result = a - b;
-            break;
-        case "modulo":
-            result = a % b;
-            break;
-        default:
-            result = Integer.MIN_VALUE;
-        }
-        return result;
-    }
-
-    public int calculateUsingSwitch(int a, int b, Operator operator) {
-        int result = 0;
-        switch (operator) {
-        case ADD:
-            result = a + b;
-            break;
-        case MULTIPLY:
-            result = a * b;
-            break;
-        case DIVIDE:
-            result = a / b;
-            break;
-        case SUBTRACT:
-            result = a - b;
-            break;
-        case MODULO:
-            result = a % b;
-            break;
-        default:
-            result = Integer.MIN_VALUE;
-        }
-        return result;
-    }
-
-    public int calculate(int a, int b, Operator operator) {
-        return operator.apply(a, b);
-    }
-
-    public int calculateUsingFactory(int a, int b, String operation) {
-        Operation targetOperation = OperatorFactory.getOperation(operation)
-            .orElseThrow(() -> new IllegalArgumentException("Invalid Operator"));
-        return targetOperation.apply(a, b);
-    }
-
-    public int calculate(Command command) {
-        return command.execute();
-    }
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/Command.java

@@ -1,5 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public interface Command {
-    Integer execute();
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/Division.java

@@ -1,7 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public class Division implements Operation {
-        @Override public int apply(int a, int b) {
-                return a / b;
-        }
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/Expression.java

@@ -1,26 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public class Expression {
-
-        private Integer x;
-        private Integer y;
-        private Operator operator;
-
-        public Expression(Integer x, Integer y, Operator operator) {
-                this.x = x;
-                this.y = y;
-                this.operator = operator;
-        }
-
-        public Integer getX() {
-                return x;
-        }
-
-        public Integer getY() {
-                return y;
-        }
-
-        public Operator getOperator() {
-                return operator;
-        }
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/Modulo.java

@@ -1,7 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public class Modulo implements Operation {
-        @Override public int apply(int a, int b) {
-                return a % b;
-        }
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/Multiplication.java

@@ -1,7 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public class Multiplication implements Operation {
-        @Override public int apply(int a, int b) {
-                return 0;
-        }
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/Operation.java

@@ -1,5 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public interface Operation {
-    int apply(int a, int b);
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/Operator.java

@@ -1,41 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public enum Operator {
-
-    ADD {
-        @Override
-        public int apply(int a, int b) {
-            return a + b;
-        }
-    },
-
-    MULTIPLY {
-        @Override
-        public int apply(int a, int b) {
-            return a * b;
-        }
-    },
-
-    SUBTRACT {
-        @Override
-        public int apply(int a, int b) {
-            return a - b;
-        }
-    },
-
-    DIVIDE {
-        @Override
-        public int apply(int a, int b) {
-            return a / b;
-        }
-    },
-
-    MODULO {
-        @Override
-        public int apply(int a, int b) {
-            return a % b;
-        }
-    };
-
-    public abstract int apply(int a, int b);
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/OperatorFactory.java

@@ -1,21 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-import java.util.HashMap;
-import java.util.Map;
-import java.util.Optional;
-
-public class OperatorFactory {
-
-    static Map<String, Operation> operationMap = new HashMap<>();
-    static {
-        operationMap.put("add", new Addition());
-        operationMap.put("divide", new Division());
-        operationMap.put("multiply", new Multiplication());
-        operationMap.put("subtract", new Subtraction());
-        operationMap.put("modulo", new Modulo());
-    }
-
-    public static Optional<Operation> getOperation(String operation) {
-        return Optional.ofNullable(operationMap.get(operation));
-    }
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/Result.java

@@ -1,13 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public class Result {
-    int value;
-
-    public Result(int value) {
-        this.value = value;
-    }
-
-    public int getValue() {
-        return value;
-    }
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/Rule.java

@@ -1,8 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public interface Rule {
-
-    boolean evaluate(Expression expression);
-
-    Result getResult();
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/RuleEngine.java

@@ -1,24 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-import java.util.ArrayList;
-import java.util.List;
-import java.util.Optional;
-import java.util.stream.Collectors;
-
-public class RuleEngine {
-
-    private static List<Rule> rules = new ArrayList<>();
-
-    static {
-        rules.add(new AddRule());
-    }
-
-    public Result process(Expression expression) {
-
-        Rule rule = rules.stream()
-            .filter(r -> r.evaluate(expression))
-            .findFirst()
-            .orElseThrow(() -> new IllegalArgumentException("Expression does not matches any Rule"));
-        return rule.getResult();
-    }
-}

core-java-modules/core-java-8/src/main/java/com/baeldung/reducingIfElse/Subtraction.java

@@ -1,7 +0,0 @@
-package com.baeldung.reducingIfElse;
-
-public class Subtraction implements Operation {
-        @Override public int apply(int a, int b) {
-                return a - b;
-        }
-}

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/counter/CounterStatistics.java

@@ -1,61 +0,0 @@
-package com.baeldung.counter;
-
-import java.util.HashMap;
-import java.util.Map;
-import java.util.Random;
-
-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 com.baeldung.counter.CounterUtil.MutableInteger;
-
-@Fork(value = 1, warmups = 3)
-@BenchmarkMode(Mode.All)
-public class CounterStatistics {
-
-    private static final Map<String, Integer> counterMap = new HashMap<>();
-    private static final Map<String, MutableInteger> counterWithMutableIntMap = new HashMap<>();
-    private static final Map<String, int[]> counterWithIntArrayMap = new HashMap<>();
-    private static final Map<String, Long> counterWithLongWrapperMap = new HashMap<>();
-    private static final Map<String, Long> counterWithLongWrapperStreamMap = new HashMap<>();
-    
-    static {
-        CounterUtil.COUNTRY_NAMES = new String[10000];
-        final String prefix = "NewString"; 
-        Random random = new Random();
-        for (int i=0; i<10000; i++) {
-            CounterUtil.COUNTRY_NAMES[i] = new String(prefix + random.nextInt(1000));
-        }
-    }
-
-  @Benchmark
-    public void wrapperAsCounter() {
-        CounterUtil.counterWithWrapperObject(counterMap);
-    }
-
-    @Benchmark
-    public void lambdaExpressionWithWrapper() {
-        CounterUtil.counterWithLambdaAndWrapper(counterWithLongWrapperMap);
-    }
-    
-    @Benchmark
-    public void parallelStreamWithWrapper() {
-        CounterUtil.counterWithParallelStreamAndWrapper(counterWithLongWrapperStreamMap);
-    }
-
-    @Benchmark
-    public void mutableIntegerAsCounter() {
-        CounterUtil.counterWithMutableInteger(counterWithMutableIntMap);
-    }
-
-    @Benchmark
-    public void primitiveArrayAsCounter() {
-        CounterUtil.counterWithPrimitiveArray(counterWithIntArrayMap);
-    }
-
-    public static void main(String[] args) throws Exception {
-        org.openjdk.jmh.Main.main(args);
-    }
-}

core-java-modules/core-java-8/src/test/java/com/baeldung/counter/CounterUnitTest.java

@@ -1,53 +0,0 @@
-package com.baeldung.counter;
-
-import java.util.HashMap;
-import java.util.Map;
-
-import static org.junit.Assert.*;
-
-import org.junit.Test;
-
-import com.baeldung.counter.CounterUtil.MutableInteger;
-
-public class CounterUnitTest {
-
-    @Test
-    public void whenMapWithWrapperAsCounter_runsSuccessfully() {
-        Map<String, Integer> counterMap = new HashMap<>();
-        CounterUtil.counterWithWrapperObject(counterMap);
-
-        assertEquals(3, counterMap.get("China")
-            .intValue());
-        assertEquals(2, counterMap.get("India")
-            .intValue());
-    }
-
-    @Test
-    public void whenMapWithLambdaAndWrapperCounter_runsSuccessfully() {
-        Map<String, Long> counterMap = new HashMap<>();
-        CounterUtil.counterWithLambdaAndWrapper(counterMap);
-
-        assertEquals(3l, counterMap.get("China")
-            .longValue());
-        assertEquals(2l, counterMap.get("India")
-            .longValue());
-    }
-
-    @Test
-    public void whenMapWithMutableIntegerCounter_runsSuccessfully() {
-        Map<String, MutableInteger> counterMap = new HashMap<>();
-        CounterUtil.counterWithMutableInteger(counterMap);
-        assertEquals(3, counterMap.get("China")
-            .getCount());
-        assertEquals(2, counterMap.get("India")
-            .getCount());
-    }
-
-    @Test
-    public void whenMapWithPrimitiveArray_runsSuccessfully() {
-        Map<String, int[]> counterMap = new HashMap<>();
-        CounterUtil.counterWithPrimitiveArray(counterMap);
-        assertEquals(3, counterMap.get("China")[0]);
-        assertEquals(2, counterMap.get("India")[0]);
-    }
-}

core-java-modules/core-java-8/src/test/java/com/baeldung/counter/CounterUtil.java

@@ -1,57 +0,0 @@
-package com.baeldung.counter;
-
-import java.util.Map;
-import java.util.stream.Collectors;
-import java.util.stream.Stream;
-
-public class CounterUtil {
-
-    public static String[] COUNTRY_NAMES = { "China", "Australia", "India", "USA", "USSR", "UK", "China", "France", "Poland", "Austria", "India", "USA", "Egypt", "China" };
-
-    public static void counterWithWrapperObject(Map<String, Integer> counterMap) {
-        for (String country : COUNTRY_NAMES) {
-            counterMap.compute(country, (k, v) -> v == null ? 1 : v + 1);
-        }
-    }
-
-    public static void counterWithLambdaAndWrapper(Map<String, Long> counterMap) {
-        Stream.of(COUNTRY_NAMES)
-            .collect(Collectors.groupingBy(k -> k, () -> counterMap, Collectors.counting()));
-    }
-
-    public static void counterWithParallelStreamAndWrapper(Map<String, Long> counterMap) {
-        Stream.of(COUNTRY_NAMES)
-            .parallel()
-            .collect(Collectors.groupingBy(k -> k, () -> counterMap, Collectors.counting()));
-    }
-
-    public static class MutableInteger {
-        int count;
-
-        public MutableInteger(int count) {
-            this.count = count;
-        }
-
-        public void increment() {
-            this.count++;
-        }
-
-        public int getCount() {
-            return this.count;
-        }
-    }
-
-    public static void counterWithMutableInteger(Map<String, MutableInteger> counterMap) {
-        for (String country : COUNTRY_NAMES) {
-            counterMap.compute(country, (k, v) -> v == null ? new MutableInteger(0) : v)
-                .increment();
-        }
-    }
-
-    public static void counterWithPrimitiveArray(Map<String, int[]> counterMap) {
-        for (String country : COUNTRY_NAMES) {
-            counterMap.compute(country, (k, v) -> v == null ? new int[] { 0 } : v)[0]++;
-        }
-    }
-
-}

core-java-modules/core-java-8/src/test/java/com/baeldung/java8/JavaTryWithResourcesLongRunningUnitTest.java

@@ -1,92 +0,0 @@
-package com.baeldung.java8;
-
-import java.io.PrintWriter;
-import java.io.StringWriter;
-import java.util.Date;
-import java.util.Scanner;
-
-import org.junit.Assert;
-import org.junit.Test;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-public class JavaTryWithResourcesLongRunningUnitTest {
-
-    private static final Logger LOG = LoggerFactory.getLogger(JavaTryWithResourcesLongRunningUnitTest.class);
-
-    private static final String TEST_STRING_HELLO_WORLD = "Hello World";
-    private Date resource1Date, resource2Date;
-
-    // tests
-
-    /* Example for using Try_with_resources */
-    @Test
-    public void whenWritingToStringWriter_thenCorrectlyWritten() {
-        final StringWriter sw = new StringWriter();
-        try (PrintWriter pw = new PrintWriter(sw, true)) {
-            pw.print(TEST_STRING_HELLO_WORLD);
-        }
-
-        Assert.assertEquals(sw.getBuffer()
-            .toString(), TEST_STRING_HELLO_WORLD);
-    }
-
-    /* Example for using multiple resources */
-    @Test
-    public void givenStringToScanner_whenWritingToStringWriter_thenCorrectlyWritten() {
-
-        final StringWriter sw = new StringWriter();
-        try (Scanner sc = new Scanner(TEST_STRING_HELLO_WORLD); PrintWriter pw = new PrintWriter(sw, true)) {
-            while (sc.hasNext()) {
-                pw.print(sc.nextLine());
-            }
-        }
-
-        Assert.assertEquals(sw.getBuffer()
-            .toString(), TEST_STRING_HELLO_WORLD);
-    }
-
-    /* Example to show order in which the resources are closed */
-    @Test
-    public void whenFirstAutoClosableResourceIsinitializedFirst_thenFirstAutoClosableResourceIsReleasedFirst() throws Exception {
-        try (AutoCloseableResourcesFirst af = new AutoCloseableResourcesFirst(); AutoCloseableResourcesSecond as = new AutoCloseableResourcesSecond()) {
-            af.doSomething();
-            as.doSomething();
-        }
-        Assert.assertTrue(resource1Date.after(resource2Date));
-    }
-
-    class AutoCloseableResourcesFirst implements AutoCloseable {
-        public AutoCloseableResourcesFirst() {
-            LOG.debug("Constructor -> AutoCloseableResources_First");
-        }
-
-        public void doSomething() {
-            LOG.debug("Something -> AutoCloseableResources_First");
-        }
-
-        @Override
-        public void close() throws Exception {
-            LOG.debug("Closed AutoCloseableResources_First");
-            resource1Date = new Date();
-        }
-    }
-
-    class AutoCloseableResourcesSecond implements AutoCloseable {
-        public AutoCloseableResourcesSecond() {
-            LOG.debug("Constructor -> AutoCloseableResources_Second");
-        }
-
-        public void doSomething() {
-            LOG.debug("Something -> AutoCloseableResources_Second");
-        }
-
-        @Override
-        public void close() throws Exception {
-            LOG.debug("Closed AutoCloseableResources_Second");
-            resource2Date = new Date();
-            Thread.sleep(10000);
-        }
-    }
-
-}

core-java-modules/core-java-8/src/test/java/com/baeldung/java_8_features/groupingby/Java8GroupingByCollectorUnitTest.java

@@ -1,15 +1,32 @@
-package com.baeldung.java8;
-
-import com.baeldung.java_8_features.groupingby.BlogPost;
-import com.baeldung.java_8_features.groupingby.BlogPostType;
-import org.junit.Test;
-
-import java.util.*;
-import java.util.concurrent.ConcurrentMap;
+package com.baeldung.java_8_features.groupingby;
 
 import static java.util.Comparator.comparingInt;
-import static java.util.stream.Collectors.*;
-import static org.junit.Assert.*;
+import static java.util.stream.Collectors.averagingInt;
+import static java.util.stream.Collectors.counting;
+import static java.util.stream.Collectors.groupingBy;
+import static java.util.stream.Collectors.groupingByConcurrent;
+import static java.util.stream.Collectors.joining;
+import static java.util.stream.Collectors.mapping;
+import static java.util.stream.Collectors.maxBy;
+import static java.util.stream.Collectors.summarizingInt;
+import static java.util.stream.Collectors.summingInt;
+import static java.util.stream.Collectors.toList;
+import static java.util.stream.Collectors.toSet;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+
+import java.util.Arrays;
+import java.util.EnumMap;
+import java.util.IntSummaryStatistics;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.ConcurrentMap;
+
+import org.junit.Test;
 
 public class Java8GroupingByCollectorUnitTest {
 
@@ -180,4 +197,19 @@ public class Java8GroupingByCollectorUnitTest {
         assertEquals(15, newsLikeStatistics.getMin());
     }
 
+    @Test
+    public void givenAListOfPosts_whenGroupedByComplexMapKeyType_thenGetAMapBetweenTupleAndList() {
+        Map<Tuple, List<BlogPost>> postsPerTypeAndAuthor = posts.stream()
+            .collect(groupingBy(post -> new Tuple(post.getType(), post.getAuthor())));
+
+        List<BlogPost> result = postsPerTypeAndAuthor.get(new Tuple(BlogPostType.GUIDE, "Author 1"));
+
+        assertThat(result.size()).isEqualTo(1);
+
+        BlogPost blogPost = result.get(0);
+
+        assertThat(blogPost.getTitle()).isEqualTo("Programming guide");
+        assertThat(blogPost.getType()).isEqualTo(BlogPostType.GUIDE);
+        assertThat(blogPost.getAuthor()).isEqualTo("Author 1");
+    }
 }

core-java-modules/core-java-8/src/test/java/com/baeldung/optional/PersonRepositoryUnitTest.java

@@ -1,43 +0,0 @@
-package com.baeldung.optional;
-
-import org.junit.Test;
-
-import java.util.Optional;
-
-import static org.junit.jupiter.api.Assertions.assertAll;
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertThrows;
-
-public class PersonRepositoryUnitTest {
-
-    PersonRepository personRepository = new PersonRepository();
-
-    @Test
-    public void whenIdIsNull_thenExceptionIsThrown() {
-        assertThrows(IllegalArgumentException.class,
-                () ->
-                        Optional
-                                .ofNullable(personRepository.findNameById(null))
-                                .orElseThrow(IllegalArgumentException::new));
-    }
-
-    @Test
-    public void whenIdIsNonNull_thenNoExceptionIsThrown() {
-        assertAll(
-                () ->
-                        Optional
-                                .ofNullable(personRepository.findNameById("id"))
-                                .orElseThrow(RuntimeException::new));
-    }
-
-    @Test
-    public void whenIdNonNull_thenReturnsNameUpperCase() {
-        String name = Optional
-                .ofNullable(personRepository.findNameById("id"))
-                .map(String::toUpperCase)
-                .orElseThrow(RuntimeException::new);
-
-        assertEquals("NAME", name);
-    }
-
-}

core-java-modules/core-java-8/src/test/java/com/baeldung/reduceIfelse/CalculatorUnitTest.java

@@ -1,39 +0,0 @@
-package com.baeldung.reduceIfelse;
-
-import com.baeldung.reducingIfElse.AddCommand;
-import com.baeldung.reducingIfElse.Calculator;
-import com.baeldung.reducingIfElse.Operator;
-import org.junit.Test;
-
-import static org.junit.Assert.assertEquals;
-
-public class CalculatorUnitTest {
-
-    @Test
-    public void whenCalculateUsingStringOperator_thenReturnCorrectResult() {
-        Calculator calculator = new Calculator();
-        int result = calculator.calculate(3, 4, "add");
-        assertEquals(7, result);
-    }
-
-    @Test
-    public void whenCalculateUsingEnumOperator_thenReturnCorrectResult() {
-        Calculator calculator = new Calculator();
-        int result = calculator.calculate(3, 4, Operator.valueOf("ADD"));
-        assertEquals(7, result);
-    }
-
-    @Test
-    public void whenCalculateUsingCommand_thenReturnCorrectResult() {
-        Calculator calculator = new Calculator();
-        int result = calculator.calculate(new AddCommand(3, 7));
-        assertEquals(10, result);
-    }
-
-    @Test
-    public void whenCalculateUsingFactory_thenReturnCorrectResult() {
-        Calculator calculator = new Calculator();
-        int result = calculator.calculateUsingFactory(3, 4, "add");
-        assertEquals(7, result);
-    }
-}

core-java-modules/core-java-8/src/test/java/com/baeldung/reduceIfelse/RuleEngineUnitTest.java

@@ -1,23 +0,0 @@
-package com.baeldung.reduceIfelse;
-
-import com.baeldung.reducingIfElse.Expression;
-import com.baeldung.reducingIfElse.Operator;
-import com.baeldung.reducingIfElse.Result;
-import com.baeldung.reducingIfElse.RuleEngine;
-import org.junit.Test;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertNotNull;
-
-public class RuleEngineUnitTest {
-
-    @Test
-    public void whenNumbersGivenToRuleEngine_thenReturnCorrectResult() {
-        Expression expression = new Expression(5, 5, Operator.ADD);
-        RuleEngine engine = new RuleEngine();
-        Result result = engine.process(expression);
-
-        assertNotNull(result);
-        assertEquals(10, result.getValue());
-    }
-}

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>