Merge pull request #73 from eugenp/master

update

aws-lambda/README.md

@@ -5,3 +5,4 @@ This module contains articles about AWS Lambda
 ### Relevant Articles: 
 - [Using AWS Lambda with API Gateway](https://www.baeldung.com/aws-lambda-api-gateway)
 - [Introduction to AWS Serverless Application Model](https://www.baeldung.com/aws-serverless)
+- [How to Implement Hibernate in an AWS Lambda Function in Java](https://www.baeldung.com/java-aws-lambda-hibernate)

core-groovy-strings/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [How to Remove a Prefix From Strings in Groovy](https://www.baeldung.com/groovy-remove-string-prefix)

core-groovy-strings/pom.xml

@@ -0,0 +1,122 @@
+<?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-groovy-strings</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <name>core-groovy-strings</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.codehaus.groovy</groupId>
+            <artifactId>groovy</artifactId>
+            <version>${groovy.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.codehaus.groovy</groupId>
+            <artifactId>groovy-all</artifactId>
+            <version>${groovy-all.version}</version>
+            <type>pom</type>
+        </dependency>
+        <dependency>
+            <groupId>org.codehaus.groovy</groupId>
+            <artifactId>groovy-dateutil</artifactId>
+            <version>${groovy.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.codehaus.groovy</groupId>
+            <artifactId>groovy-sql</artifactId>
+            <version>${groovy-sql.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.platform</groupId>
+            <artifactId>junit-platform-runner</artifactId>
+            <version>${junit.platform.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.hsqldb</groupId>
+            <artifactId>hsqldb</artifactId>
+            <version>${hsqldb.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.spockframework</groupId>
+            <artifactId>spock-core</artifactId>
+            <version>${spock-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.codehaus.gmavenplus</groupId>
+                <artifactId>gmavenplus-plugin</artifactId>
+                <version>${gmavenplus-plugin.version}</version>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>addSources</goal>
+                            <goal>addTestSources</goal>
+                            <goal>compile</goal>
+                            <goal>compileTests</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <artifactId>maven-failsafe-plugin</artifactId>
+                <version>${maven-failsafe-plugin.version}</version>
+                <dependencies>
+                    <dependency>
+                        <groupId>org.junit.platform</groupId>
+                        <artifactId>junit-platform-surefire-provider</artifactId>
+                        <version>${junit.platform.version}</version>
+                    </dependency>
+                </dependencies>
+                <executions>
+                    <execution>
+                        <id>junit5</id>
+                        <goals>
+                            <goal>integration-test</goal>
+                            <goal>verify</goal>
+                        </goals>
+                        <configuration>
+                            <includes>
+                                <include>**/*Test5.java</include>
+                            </includes>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+    <repositories>
+        <repository>
+            <id>central</id>
+            <url>https://jcenter.bintray.com</url>
+        </repository>
+    </repositories>
+
+    <properties>
+        <junit.platform.version>1.0.0</junit.platform.version>
+        <groovy.version>2.5.6</groovy.version>
+        <groovy-all.version>2.5.6</groovy-all.version>
+        <groovy-sql.version>2.5.6</groovy-sql.version>
+        <hsqldb.version>2.4.0</hsqldb.version>
+        <spock-core.version>1.1-groovy-2.4</spock-core.version>
+        <gmavenplus-plugin.version>1.6</gmavenplus-plugin.version>
+    </properties>
+
+</project>

core-groovy-strings/src/test/groovy/com/baeldung/removeprefix/RemovePrefixTest.groovy

@@ -0,0 +1,70 @@
+package com.baeldung.removeprefix
+
+import org.junit.Assert
+import org.junit.Test
+
+class RemovePrefixTest {
+
+
+    @Test
+    public void whenCasePrefixIsRemoved_thenReturnTrue() {
+        def trimPrefix = {
+            it.startsWith('Groovy-') ? it.minus('Groovy-') : it
+        }
+        
+        def actual = trimPrefix("Groovy-Tutorials at Baeldung")
+        def expected = "Tutorials at Baeldung"
+
+        Assert.assertEquals(expected, actual)
+    }
+
+    @Test
+    public void whenPrefixIsRemoved_thenReturnTrue() {
+
+        String prefix = "groovy-"
+        String trimPrefix = "Groovy-Tutorials at Baeldung"
+        def actual;
+        if(trimPrefix.startsWithIgnoreCase(prefix)) {
+            actual = trimPrefix.substring(prefix.length())
+        }
+        
+        def expected = "Tutorials at Baeldung"
+
+        Assert.assertEquals(expected, actual)
+    }
+
+    @Test
+    public void whenPrefixIsRemovedUsingRegex_thenReturnTrue() {
+
+        def regex = ~"^([Gg])roovy-"
+        String trimPrefix = "Groovy-Tutorials at Baeldung"
+        String actual = trimPrefix - regex
+        
+        def expected = "Tutorials at Baeldung"
+
+        Assert.assertEquals(expected, actual)
+    }
+
+    @Test 
+    public void whenPrefixIsRemovedUsingReplaceFirst_thenReturnTrue() {
+        def regex = ~"^groovy" 
+        String trimPrefix = "groovyTutorials at Baeldung's groovy page" 
+        String actual = trimPrefix.replaceFirst(regex, "")
+        
+        def expected = "Tutorials at Baeldung's groovy page"
+        
+        Assert.assertEquals(expected, actual)
+    }
+
+    @Test
+    public void whenPrefixIsRemovedUsingReplaceAll_thenReturnTrue() {
+
+        String trimPrefix = "groovyTutorials at Baeldung groovy"
+        String actual = trimPrefix.replaceAll(/^groovy/, "")
+        
+        def expected = "Tutorials at Baeldung groovy"
+
+        Assert.assertEquals(expected, actual)
+    }
+
+}

core-java-modules/core-java-10/src/test/java/com/baeldung/AppUnitTest.java

@@ -7,7 +7,7 @@ import junit.framework.TestSuite;
 /**
  * Unit test for simple App.
  */
-public class AppTest 
+public class AppUnitTest
     extends TestCase
 {
     /**
@@ -15,7 +15,7 @@ public class AppTest
      *
      * @param testName name of the test case
      */
-    public AppTest( String testName )
+    public AppUnitTest(String testName )
     {
         super( testName );
     }
@@ -25,7 +25,7 @@ public class AppTest
      */
     public static Test suite()
     {
-        return new TestSuite( AppTest.class );
+        return new TestSuite( AppUnitTest.class );
     }
 
     /**

core-java-modules/core-java-12/src/test/java/com/baeldung/string/StringAPIUnitTest.java

@@ -5,7 +5,7 @@ import static org.hamcrest.MatcherAssert.assertThat;
 
 import org.junit.Test;
 
-public class StringAPITest {
+public class StringAPIUnitTest {
 
     @Test
     public void whenPositiveArgument_thenReturnIndentedString() {

core-java-modules/core-java-14/src/test/java/com/baeldung/java14/record/PersonUnitTest.java

@@ -7,7 +7,7 @@ import static org.junit.Assert.assertTrue;
 
 import org.junit.Test;
 
-public class PersonTest {
+public class PersonUnitTest {
 
     @Test
     public void givenSameNameAndAddress_whenEquals_thenPersonsEqual() {

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

@@ -44,6 +44,16 @@
             <artifactId>commons-collections4</artifactId>
             <version>${commons-collections4.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>3.11</version>
+        </dependency>
+        <dependency>
+            <groupId>commons-io</groupId>
+            <artifactId>commons-io</artifactId>
+            <version>2.7</version>
+        </dependency>
     </dependencies>
 
     <build>
@@ -77,6 +87,7 @@
         <maven.compiler.target>1.9</maven.compiler.target>
         <guava.version>25.1-jre</guava.version>
         <commons-collections4.version>4.1</commons-collections4.version>
+        <commons-collections3.version>3.2.2</commons-collections3.version>
     </properties>
 
 </project>

core-java-modules/core-java-9/src/test/java/com/baeldung/java9/methodhandles/MethodHandlesUnitTest.java

@@ -17,7 +17,7 @@ import org.junit.Test;
 /**
  * Test case for the {@link MethodHandles} API
  */
-public class MethodHandlesTest {
+public class MethodHandlesUnitTest {
 
     @Test
     public void givenConcatMethodHandle_whenInvoked_thenCorrectlyConcatenated() throws Throwable {

core-java-modules/core-java-arrays-guides/README.md

@@ -6,3 +6,4 @@ This module contains complete guides about arrays in Java
 - [Arrays in Java: A Reference Guide](https://www.baeldung.com/java-arrays-guide)
 - [Guide to the java.util.Arrays Class](https://www.baeldung.com/java-util-arrays)
 - [What is \[Ljava.lang.Object;?](https://www.baeldung.com/java-tostring-array)
+- [Guide to ArrayStoreException](https://www.baeldung.com/java-arraystoreexception)

core-java-modules/core-java-collections-3/src/main/java/com/baeldung/collections/removeallperformance/HashSetBenchmark.java

@@ -0,0 +1,86 @@
+package com.baeldung.collections.removeallperformance;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+
+import org.apache.commons.lang3.RandomStringUtils;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Level;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+import com.baeldung.collections.containsperformance.Employee;
+
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@Warmup(iterations = 5)
+public class HashSetBenchmark {
+
+    @State(Scope.Thread)
+    public static class MyState {
+        private Set<Employee> employeeSet1 = new HashSet<>();
+        private List<Employee> employeeList1 = new ArrayList<>();
+        private Set<Employee> employeeSet2 = new HashSet<>();
+        private List<Employee> employeeList2 = new ArrayList<>();
+
+        private long set1Size = 60000;
+        private long list1Size = 50000;
+        private long set2Size = 50000;
+        private long list2Size = 60000;
+
+        @Setup(Level.Trial)
+        public void setUp() {
+
+            for (long i = 0; i < set1Size; i++) {
+                employeeSet1.add(new Employee(i, RandomStringUtils.random(7, true, false)));
+            }
+
+            for (long i = 0; i < list1Size; i++) {
+                employeeList1.add(new Employee(i, RandomStringUtils.random(7, true, false)));
+            }
+
+            for (long i = 0; i < set2Size; i++) {
+                employeeSet2.add(new Employee(i, RandomStringUtils.random(7, true, false)));
+            }
+
+            for (long i = 0; i < list2Size; i++) {
+                employeeList2.add(new Employee(i, RandomStringUtils.random(7, true, false)));
+            }
+
+        }
+
+    }
+
+    @Benchmark
+    public boolean given_SizeOfHashsetGreaterThanSizeOfCollection_When_RemoveAllFromHashSet_Then_GoodPerformance(MyState state) {
+        return state.employeeSet1.removeAll(state.employeeList1);
+    }
+
+    @Benchmark
+    public boolean given_SizeOfHashsetSmallerThanSizeOfCollection_When_RemoveAllFromHashSet_Then_BadPerformance(MyState state) {
+        return state.employeeSet2.removeAll(state.employeeList2);
+    }
+
+    public static void main(String[] args) throws Exception {
+        Options options = new OptionsBuilder().include(HashSetBenchmark.class.getSimpleName())
+            .threads(1)
+            .forks(1)
+            .shouldFailOnError(true)
+            .shouldDoGC(true)
+            .jvmArgs("-server")
+            .build();
+        new Runner(options).run();
+    }
+
+}

core-java-modules/core-java-collections-3/src/test/java/com/baeldung/collections/hashset/HashSetUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.collections.hashset;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+
+import org.junit.jupiter.api.Test;
+
+class HashSetUnitTest {
+
+    @Test
+    void whenRemoveAllFromHashset_thenRemovesAllElementsFromHashsetThatArePresentInCollection() {
+        Set<Integer> set = new HashSet<>();
+        Collection<Integer> collection = new ArrayList<>();
+        set.add(1);
+        set.add(2);
+        set.add(3);
+        set.add(4);
+        collection.add(1);
+        collection.add(3);
+
+        set.removeAll(collection);
+
+        assertEquals(2, set.size());
+        Integer[] actualElements = new Integer[set.size()];
+        Integer[] expectedElements = new Integer[] { 2, 4 };
+        assertArrayEquals(expectedElements, set.toArray(actualElements));
+    }
+
+}

core-java-modules/core-java-collections-3/src/test/java/com/baeldung/collections/mapfirstpair/MapFirstPairUnitTest.java

@@ -15,21 +15,24 @@ import org.junit.Test;
 public class MapFirstPairUnitTest {
 
     private Map.Entry<Integer, String> getFirstPairUsingIterator(Map<Integer, String> map) {
-        if (map == null || map.size() == 0)
+        if (map == null || map.size() == 0) {
             return null;
+        }
 
         Iterator<Map.Entry<Integer, String>> iterator = map.entrySet()
             .iterator();
 
-        if (iterator.hasNext())
+        if (iterator.hasNext()) {
             return iterator.next();
+        }
 
         return null;
     }
 
     private Map.Entry<Integer, String> getFirstPairUsingStream(Map<Integer, String> map) {
-        if (map == null || map.size() == 0)
+        if (map == null || map.size() == 0) {
             return null;
+        }
 
         Set<Map.Entry<Integer, String>> entrySet = map.entrySet();
 

core-java-modules/core-java-date-operations-1/src/test/java/com/baeldung/date/DateDiffUnitTest.java

@@ -1,6 +1,8 @@
 package com.baeldung.date;
 
-import static org.junit.Assert.assertEquals;
+import org.joda.time.Days;
+import org.joda.time.Minutes;
+import org.junit.Test;
 
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
@@ -16,7 +18,7 @@ import java.util.Locale;
 import java.util.TimeZone;
 import java.util.concurrent.TimeUnit;
 
-import org.junit.Test;
+import static org.junit.Assert.*;
 
 public class DateDiffUnitTest {
 
@@ -29,18 +31,39 @@ public class DateDiffUnitTest {
         long diffInMillies = Math.abs(secondDate.getTime() - firstDate.getTime());
         long diff = TimeUnit.DAYS.convert(diffInMillies, TimeUnit.MILLISECONDS);
 
-        assertEquals(diff, 6);
+        assertEquals(6, diff);
     }
 
     @Test
-    public void givenTwoDatesInJava8_whenDifferentiating_thenWeGetSix() {
-        LocalDate now = LocalDate.now();
-        LocalDate sixDaysBehind = now.minusDays(6);
+    public void givenTwoDatesInJava8_whenUsingPeriodGetDays_thenWorks() {
+        LocalDate aDate = LocalDate.of(2020, 9, 11);
+        LocalDate sixDaysBehind = aDate.minusDays(6);
 
-        Period period = Period.between(now, sixDaysBehind);
+        Period period = Period.between(aDate, sixDaysBehind);
         int diff = Math.abs(period.getDays());
 
-        assertEquals(diff, 6);
+        assertEquals(6, diff);
+    }
+
+    @Test
+    public void givenTwoDatesInJava8_whenUsingPeriodGetDays_thenDoesNotWork() {
+        LocalDate aDate = LocalDate.of(2020, 9, 11);
+        LocalDate sixtyDaysBehind = aDate.minusDays(60);
+        Period period = Period.between(aDate, sixtyDaysBehind);
+        int diff = Math.abs(period.getDays());
+        //not equals
+        assertNotEquals(60, diff);
+    }
+
+    @Test
+    public void givenTwoDatesInJava8_whenUsingPeriod_thenWeGet0Year1Month29Days() {
+        LocalDate aDate = LocalDate.of(2020, 9, 11);
+        LocalDate sixtyDaysBehind = aDate.minusDays(60);
+        Period period = Period.between(aDate, sixtyDaysBehind);
+        int years = Math.abs(period.getYears());
+        int months = Math.abs(period.getMonths());
+        int days = Math.abs(period.getDays());
+        assertArrayEquals(new int[] { 0, 1, 29 }, new int[] { years, months, days });
     }
 
     @Test
@@ -51,7 +74,7 @@ public class DateDiffUnitTest {
         Duration duration = Duration.between(now, sixMinutesBehind);
         long diff = Math.abs(duration.toMinutes());
 
-        assertEquals(diff, 6);
+        assertEquals(6, diff);
     }
 
     @Test
@@ -61,7 +84,7 @@ public class DateDiffUnitTest {
 
         long diff = ChronoUnit.SECONDS.between(now, tenSecondsLater);
 
-        assertEquals(diff, 10);
+        assertEquals(10, diff);
     }
 
     @Test
@@ -71,7 +94,7 @@ public class DateDiffUnitTest {
         ZonedDateTime sixDaysBehind = now.withZoneSameInstant(ZoneId.of("Asia/Singapore"))
                                          .minusDays(6);
         long diff = ChronoUnit.DAYS.between(sixDaysBehind, now);
-        assertEquals(diff, 6);
+        assertEquals(6, diff);
     }
 
     @Test
@@ -81,7 +104,7 @@ public class DateDiffUnitTest {
 
         long diff = now.until(tenSecondsLater, ChronoUnit.SECONDS);
 
-        assertEquals(diff, 10);
+        assertEquals(10, diff);
     }
 
     @Test
@@ -89,10 +112,9 @@ public class DateDiffUnitTest {
         org.joda.time.LocalDate now = org.joda.time.LocalDate.now();
         org.joda.time.LocalDate sixDaysBehind = now.minusDays(6);
 
-        org.joda.time.Period period = new org.joda.time.Period(now, sixDaysBehind);
-        long diff = Math.abs(period.getDays());
+        long diff = Math.abs(Days.daysBetween(now, sixDaysBehind).getDays());
 
-        assertEquals(diff, 6);
+        assertEquals(6, diff);
     }
 
     @Test
@@ -100,8 +122,9 @@ public class DateDiffUnitTest {
         org.joda.time.LocalDateTime now = org.joda.time.LocalDateTime.now();
         org.joda.time.LocalDateTime sixMinutesBehind = now.minusMinutes(6);
 
-        org.joda.time.Period period = new org.joda.time.Period(now, sixMinutesBehind);
-        long diff = Math.abs(period.getDays());
+        long diff = Math.abs(Minutes.minutesBetween(now, sixMinutesBehind).getMinutes());
+        assertEquals(6, diff);
+
     }
 
     @Test
@@ -111,6 +134,6 @@ public class DateDiffUnitTest {
 
         long diff = Math.abs(now.numDaysFrom(sixDaysBehind));
 
-        assertEquals(diff, 6);
+        assertEquals(6, diff);
     }
 }

core-java-modules/core-java-datetime-string/src/test/java/com/baeldung/timestamp/TimestampToStringConverterUnitTest.java

@@ -6,7 +6,7 @@ import org.junit.jupiter.api.Test;
 import java.sql.Timestamp;
 import java.time.format.DateTimeFormatter;
 
-public class TimestampToStringConverterTest {
+public class TimestampToStringConverterUnitTest {
 
     @Test
     public void givenDatePattern_whenFormatting_thenResultingStringIsCorrect() {

core-java-modules/core-java-exceptions-3/README.md

@@ -1,3 +1,5 @@
 ### Relevant Articles:
 
 - [NoSuchMethodError in Java](https://www.baeldung.com/java-nosuchmethod-error)
+- [IllegalArgumentException or NullPointerException for a Null Parameter?](https://www.baeldung.com/java-illegalargumentexception-or-nullpointerexception)
+- [IllegalMonitorStateException in Java](https://www.baeldung.com/java-illegalmonitorstateexception)

core-java-modules/core-java-io-3/README.md

@@ -9,4 +9,6 @@ This module contains articles about core Java input and output (IO)
 - [Check If a File or Directory Exists in Java](https://www.baeldung.com/java-file-directory-exists)
 - [Copy a Directory in Java](https://www.baeldung.com/java-copy-directory)
 - [Java Files Open Options](https://www.baeldung.com/java-file-options)
+- [Creating Temporary Directories in Java](https://www.baeldung.com/java-temp-directories)
+- [Reading a Line at a Given Line Number From a File in Java](https://www.baeldung.com/java-read-line-at-number)
 - [[<-- Prev]](/core-java-modules/core-java-io-2)

core-java-modules/core-java-io-3/src/test/java/com/baeldung/emptiness/DirectoryEmptinessUnitTest.java

@@ -4,6 +4,7 @@ import org.junit.Test;
 
 import java.io.File;
 import java.io.IOException;
+import java.net.URISyntaxException;
 import java.nio.file.DirectoryStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -20,8 +21,8 @@ public class DirectoryEmptinessUnitTest {
     }
 
     @Test
-    public void givenPath_whenNotDirectory_thenReturnsFalse() throws IOException {
-        Path aFile = Paths.get(getClass().getResource("/notDir.txt").getPath());
+    public void givenPath_whenNotDirectory_thenReturnsFalse() throws IOException, URISyntaxException {
+        Path aFile = Paths.get(getClass().getResource("/notDir.txt").toURI());
         assertThat(isEmpty(aFile)).isFalse();
     }
 

core-java-modules/core-java-io-3/src/test/java/com/baeldung/existence/ExistenceUnitTest.java

@@ -4,10 +4,7 @@ import org.junit.Test;
 
 import java.io.File;
 import java.io.IOException;
-import java.nio.file.Files;
-import java.nio.file.LinkOption;
-import java.nio.file.Path;
-import java.nio.file.Paths;
+import java.nio.file.*;
 import java.util.concurrent.ThreadLocalRandom;
 
 import static org.junit.Assert.assertFalse;
@@ -47,8 +44,18 @@ public class ExistenceUnitTest {
     public void givenSymbolicLink_whenTargetDoesNotExists_thenFollowOrNotBasedOnTheOptions() throws IOException {
         Path target = Files.createTempFile("baeldung", "target");
         Path symbol = Paths.get("test-link-" + ThreadLocalRandom.current().nextInt());
+        Path symbolicLink = null;
+
+        try {
+            symbolicLink = Files.createSymbolicLink(symbol, target);
+        } catch (FileSystemException ex) {
+            System.out.println("Your OS security policy prevents the current user from creating symbolic links.\n" +
+                    "Most probably you're running Windows with UAC.\n" +
+                    "If this is the case, please see - https://docs.microsoft.com/en-us/windows/security/threat-protection/security-policy-settings/create-symbolic-links\n" +
+                    "You must change your security settings to run this test under Windows.");
+            return;
+        }
 
-        Path symbolicLink = Files.createSymbolicLink(symbol, target);
         assertTrue(Files.exists(symbolicLink));
         assertTrue(Files.isSymbolicLink(symbolicLink));
         assertFalse(Files.isSymbolicLink(target));

core-java-modules/core-java-io-3/src/test/java/com/baeldung/tempdirectory/TemporaryDirectoriesUnitTest.java

@@ -4,6 +4,7 @@ import org.apache.commons.io.FileUtils;
 import org.junit.Test;
 
 import java.io.IOException;
+import java.nio.file.FileSystems;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
@@ -66,6 +67,11 @@ public class TemporaryDirectoriesUnitTest {
 
     @Test
     public void givenTempDirWithPrefixWithFileAttrs_whenCreatePlainJava_thenAttributesAreSet() throws IOException {
+        boolean isPosix = FileSystems.getDefault().supportedFileAttributeViews().contains("posix");
+
+        if(!isPosix){
+            System.out.println("You must be under a Posix Compliant Filesystem to run this test.");
+        } else {
             final FileAttribute<Set<PosixFilePermission>> attrs = PosixFilePermissions.asFileAttribute(PosixFilePermissions.fromString("r--------"));
 
             final Path tmpdir = Files.createTempDirectory(Paths.get("target"), "tmpDirPrefix", attrs);
@@ -73,3 +79,4 @@ public class TemporaryDirectoriesUnitTest {
             assertThat(tmpdir.toFile().canWrite()).isFalse();
         }
     }
+}

core-java-modules/core-java-jpms/decoupling-pattern1/consumermodule/pom.xml

@@ -17,7 +17,7 @@
     <dependencies>
         <dependency>
             <groupId>com.baeldung.servicemodule</groupId>
-            <artifactId>servicemodule</artifactId>
+            <artifactId>servicemodule1</artifactId>
             <version>${servicemodule.version}</version>
         </dependency>
     </dependencies>

core-java-modules/core-java-jpms/decoupling-pattern1/servicemodule/pom.xml

@@ -4,7 +4,8 @@
     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>servicemodule</artifactId>
+    <groupId>com.baeldung.servicemodule</groupId>
+    <artifactId>servicemodule1</artifactId>
     <packaging>jar</packaging>
 
     <parent>

core-java-modules/core-java-jpms/decoupling-pattern2/providermodule/pom.xml

@@ -17,7 +17,7 @@
     <dependencies>
         <dependency>
             <groupId>com.baeldung.servicemodule</groupId>
-            <artifactId>servicemodule</artifactId>
+            <artifactId>servicemodule2</artifactId>
             <version>${servicemodule.version}</version>
         </dependency>
     </dependencies>

core-java-modules/core-java-jpms/decoupling-pattern2/servicemodule/pom.xml

@@ -4,7 +4,8 @@
     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>servicemodule</artifactId>
+    <groupId>com.baeldung.servicemodule</groupId>
+    <artifactId>servicemodule2</artifactId>
     <version>1.0</version>
 
     <parent>

core-java-modules/core-java-lang-3/README.md

@@ -5,4 +5,5 @@ This module contains articles about core features in the Java language
 - [Class.isInstance vs Class.isAssignableFrom](https://www.baeldung.com/java-isinstance-isassignablefrom)
 - [Converting a Java String Into a Boolean](https://www.baeldung.com/java-string-to-boolean)
 - [When are Static Variables Initialized in Java?](https://www.baeldung.com/java-static-variables-initialization)
+- [Checking if a Class Exists in Java](https://www.baeldung.com/java-check-class-exists)
 - [[<-- Prev]](/core-java-modules/core-java-lang-2)

core-java-modules/core-java-lang-math-2/README.md

@@ -13,4 +13,5 @@
 - [Convert Latitude and Longitude to a 2D Point in Java](https://www.baeldung.com/java-convert-latitude-longitude)
 - [Debugging with Eclipse](https://www.baeldung.com/eclipse-debugging)
 - [Matrix Multiplication in Java](https://www.baeldung.com/java-matrix-multiplication)
+- [Largest Power of 2 That Is Less Than the Given Number](https://www.baeldung.com/java-largest-power-of-2-less-than-number)
 - More articles: [[<-- Prev]](/core-java-modules/core-java-lang-math)

core-java-modules/core-java-lang-oop-methods/README.md

@@ -9,3 +9,4 @@ This module contains articles about methods in Java
 - [Java equals() and hashCode() Contracts](https://www.baeldung.com/java-equals-hashcode-contracts)
 - [Guide to hashCode() in Java](https://www.baeldung.com/java-hashcode)
 - [The Covariant Return Type in Java](https://www.baeldung.com/java-covariant-return-type)
+- [Does a Method’s Signature Include the Return Type in Java?](https://www.baeldung.com/java-method-signature-return-type)

core-java-modules/core-java-lang-oop-methods/src/main/java/com/baeldung/signature/OverloadingErrors.java

@@ -0,0 +1,72 @@
+package com.baeldung.signature;
+
+import java.io.Serializable;
+
+public class OverloadingErrors<T extends Serializable> {
+
+    public void print() {
+        System.out.println("Signature is: print()");
+    }
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: method print() is already defined in class
+    // The method signature is independent from return type
+    public int print() {
+        System.out.println("Signature is: print()");
+        return 0;
+    }
+    */
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: method print() is already defined in class
+    // The method signature is independent from modifiers
+    private final void print() {
+        System.out.println("Signature is: print()");
+    }
+    */
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: method print() is already defined in class
+    // The method signature is independent from thrown exception declaration
+    public void print() throws IllegalStateException {
+        System.out.println("Signature is: print()");
+        throw new IllegalStateException();
+    }
+    */
+
+    public void print(int parameter) {
+        System.out.println("Signature is: print(int)");
+    }
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: method print(int) is already defined in class
+    // The method signature is independent from parameter names
+    public void print(int anotherParameter) {
+        System.out.println("Signature is: print(int)");
+    }
+    */
+
+    public void printElement(T t) {
+        System.out.println("Signature is: printElement(T)");
+    }
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java: name clash: printElement(java.io.Serializable) and printElement(T) have the same erasure
+    // Even though the signatures appear different, the compiler cannot statically bind the correct method after type erasure
+    public void printElement(Serializable o) {
+        System.out.println("Signature is: printElement(Serializable)");
+    }
+    */
+
+    public void print(Object... parameter) {
+        System.out.println("Signature is: print(Object...)");
+    }
+
+    /*
+    // Uncommenting this method will lead to a compilation error: java cannot declare both sum(Object...) and sum(Object[])
+    // Even though the signatures appear different, after compilation they both resolve to sum(Object[])
+    public void print(Object[] parameter) {
+        System.out.println("Signature is: print(Object[])");
+    }
+    */
+}

core-java-modules/core-java-lang-oop-methods/src/main/java/com/baeldung/signature/StaticBinding.java

@@ -0,0 +1,46 @@
+package com.baeldung.signature;
+
+public class StaticBinding {
+
+    public Number sum(Integer term1, Integer term2) {
+        System.out.println("Adding integers");
+        return term1 + term2;
+    }
+
+    public Number sum(Number term1, Number term2) {
+        System.out.println("Adding numbers");
+        return term1.doubleValue() + term2.doubleValue();
+    }
+
+    public Number sum(Object term1, Object term2) {
+        System.out.println("Adding objects");
+        return term1.hashCode() + term2.hashCode();
+    }
+
+    public Number sum(Object term1, Object... term2) {
+        System.out.println("Adding variable arguments: " + term2.length);
+        int result = term1.hashCode();
+        for (Object o : term2) {
+            result += o.hashCode();
+        }
+        return result;
+    }
+
+    public static void main(String[] args) {
+        StaticBinding obj = new StaticBinding();
+
+        obj.sum(2, 3); // "Adding integers" due to auto-boxing from int to Integer
+        obj.sum(Integer.valueOf(2), Integer.valueOf(3)); // "Adding integers" due to exact parameter types
+        obj.sum(2, 0x1); // "Adding integers" due to type promotion from byte to int
+
+        obj.sum((Number) 2, (Number) 3); // "Adding numbers" due to explicit cast to Number
+        obj.sum(2.0d, 3.0d); // "Adding numbers" due to auto-boxing from double to Double
+        obj.sum(Float.valueOf(2), Float.valueOf(3)); // "Adding numbers" due to polimorphism
+
+        obj.sum((Object) 2, (Object) 3); // "Adding objects" due to explicit cast to Object
+        obj.sum(2, "John"); // "Adding objects" due to polimorphism
+
+        obj.sum(new Object(), new Object(), new Object()); // "Adding variable arguments 2"
+        obj.sum(new Object(), new Object[]{new Object()}); // "Adding variable arguments 1"
+    }
+}

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

@@ -13,4 +13,5 @@ This module contains articles about networking in Java
 - [Download a File from an URL in Java](https://www.baeldung.com/java-download-file)
 - [Handling java.net.ConnectException](https://www.baeldung.com/java-net-connectexception)
 - [Getting MAC addresses in Java](https://www.baeldung.com/java-mac-address)
+- [Sending Emails with Attachments in Java](https://www.baeldung.com/java-send-emails-attachments)
 - [[<-- Prev]](/core-java-modules/core-java-networking)

core-java-modules/core-java-os/src/test/java/com/baeldung/core/pwd/CurrentDirectoryFetcherUnitTest.java

@@ -4,7 +4,7 @@ import static org.junit.Assert.assertTrue;
 
 import org.junit.Test;
 
-public class CurrentDirectoryFetcherTest {
+public class CurrentDirectoryFetcherUnitTest {
 
     private static final String CURRENT_DIR = "core-java-os";
 

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

@@ -2,3 +2,4 @@
 
 - [Reading the Value of ‘private’ Fields from a Different Class in Java](https://www.baeldung.com/java-reflection-read-private-field-value)
 - [Set Field Value With Reflection](https://www.baeldung.com/java-set-private-field-value)
+- [Checking If a Method is Static Using Reflection in Java](https://www.baeldung.com/java-check-method-is-static)

core-java-modules/core-java-reflection-2/src/main/java/com/baeldung/reflection/check/staticmethods/StaticUtility.java

@@ -0,0 +1,19 @@
+package com.baeldung.reflection.check.staticmethods;
+
+import java.time.LocalDate;
+import java.time.LocalTime;
+
+public class StaticUtility {
+
+    public static String getAuthorName() {
+        return "Umang Budhwar";
+    }
+
+    public static LocalDate getLocalDate() {
+        return LocalDate.now();
+    }
+
+    public static LocalTime getLocalTime() {
+        return LocalTime.now();
+    }
+}

core-java-modules/core-java-reflection-2/src/test/java/com/baeldung/reflection/check/staticmethods/StaticUtilityUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.reflection.check.staticmethods;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class StaticUtilityUnitTest {
+
+    @Test
+    void whenCheckStaticMethod_ThenSuccess() throws Exception {
+        Method method = StaticUtility.class.getMethod("getAuthorName", null);
+        Assertions.assertTrue(Modifier.isStatic(method.getModifiers()));
+    }
+
+    @Test
+    void whenCheckAllStaticMethods_thenSuccess() {
+        List<Method> methodList = Arrays.asList(StaticUtility.class.getMethods())
+          .stream()
+          .filter(method -> Modifier.isStatic(method.getModifiers()))
+          .collect(Collectors.toList());
+        Assertions.assertEquals(3, methodList.size());
+    }
+
+}

core-java-modules/core-java-security-2/src/test/java/com/baeldung/cipher/AvailableCiphersUnitTest.java

@@ -0,0 +1,35 @@
+package com.baeldung.cipher;
+
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.security.Provider;
+import java.security.Security;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class AvailableCiphersUnitTest {
+    private final Logger logger = LoggerFactory.getLogger(AvailableCiphersUnitTest.class);
+
+    @Test
+    public void whenGetServices_thenGetAllCipherAlgorithms() {
+        for (Provider provider : Security.getProviders()) {
+            for (Provider.Service service : provider.getServices()) {
+                logger.info(service.getAlgorithm());
+            }
+        }
+    }
+
+    @Test
+    public void whenGetServicesWithFilter_thenGetAllCompatibleCipherAlgorithms() {
+        List<String> algorithms = Arrays.stream(Security.getProviders())
+          .flatMap(provider -> provider.getServices().stream())
+          .filter(service -> "Cipher".equals(service.getType()))
+          .map(Provider.Service::getAlgorithm)
+          .collect(Collectors.toList());
+
+        algorithms.forEach(logger::info);
+    }
+}

core-java-modules/multimodulemavenproject/daomodule/pom.xml

@@ -20,6 +20,10 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
             </plugin>
         </plugins>
     </build>

core-java-modules/multimodulemavenproject/entitymodule/pom.xml

@@ -20,6 +20,10 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
             </plugin>
         </plugins>
     </build>

core-java-modules/multimodulemavenproject/mainappmodule/pom.xml

@@ -38,6 +38,10 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
             </plugin>
         </plugins>
     </build>

core-java-modules/multimodulemavenproject/userdaomodule/pom.xml

@@ -33,6 +33,10 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
             </plugin>
         </plugins>
     </build>

core-java-modules/pom.xml

@@ -18,20 +18,9 @@
 
     <modules>
         <module>core-java</module>
-        <!-- <module>core-java-10</module> --> <!-- We haven't upgraded to java 10. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-11</module> --> <!-- We haven't upgraded to java 11. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-12</module> --> <!-- We haven't upgraded to java 12. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-13</module> --> <!-- We haven't upgraded to java 12. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-14</module> --> <!-- We haven't upgraded to java 14.-->
         <module>core-java-8</module>
         <module>core-java-8-2</module>
 
-        <!-- <module>core-java-9</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-9-improvements</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-9-jigsaw</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-9-new-features</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
-        <!-- <module>core-java-9-streams</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
-
         <module>core-java-annotations</module>
 
         <module>core-java-arrays-sorting</module>
@@ -51,7 +40,6 @@
         <module>core-java-collections-maps</module>
         <module>core-java-collections-maps-2</module>
         <module>core-java-collections-maps-3</module>
-        <!-- <module>core-java-collections-set</module> --> <!-- We haven't upgraded to java 11. Fixing in BAEL-10841 -->
 
         <module>core-java-concurrency-2</module>
         <module>core-java-concurrency-advanced</module>
@@ -65,10 +53,7 @@
 
         <!--<module>core-java-8-datetime</module>--> <!-- unit test case failure -->
         <module>core-java-8-datetime-2</module>
-        <!-- <module>core-java-date-operations-1</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
         <module>core-java-date-operations-2</module>
-        <!-- We haven't upgraded to java 9. -->
-        <!-- <module>core-java-datetime-computations</module> <module>core-java-datetime-conversion</module> <module>core-java-datetime-java8</module> <module>core-java-datetime-string</module> -->
         <module>core-java-8-datetime</module>
 
         <module>core-java-exceptions</module>
@@ -85,7 +70,6 @@
 
         <module>core-java-jar</module>
         <module>core-java-jndi</module>
-        <!-- <module>core-java-jpms</module> --> <!-- We haven't upgraded to java 10. Fixing in BAEL-10841 -->
         <module>core-java-jvm</module>
         <module>core-java-jvm-2</module>
 
@@ -113,7 +97,6 @@
         <module>core-java-nio-2</module>
 
         <module>core-java-optional</module>
-        <!--<module>core-java-os</module> --> <!-- We haven't upgraded to java 9. -->
 
         <module>core-java-perf</module>
 
@@ -138,9 +121,6 @@
         <module>core-java-sun</module>
 
         <module>core-java-regex</module>
-        <!-- <module>core-java-time-measurements</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
-
-        <!-- <module>multimodulemavenproject</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
         <module>pre-jpms</module>
     </modules>
 

core-kotlin-modules/core-kotlin-collections-2/README.md

@@ -2,6 +2,6 @@
 
 This module contains articles about core Kotlin collections.
 
-### Relevant articles:
-
+## Relevant articles:
 
+- [Aggregate Operations in Kotlin](https://www.baeldung.com/kotlin/aggregate-operations)

gradle-5/cmd-line-args/README.md

@@ -0,0 +1,3 @@
+## Relevant Articles:
+
+- [Passing Command Line Arguments in Gradle](https://www.baeldung.com/gradle-command-line-arguments)

gradle-5/source-sets/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Gradle Source Sets](https://www.baeldung.com/gradle-source-sets)

gradle/gradle-wrapper/gradle/wrapper/README.md

@@ -0,0 +1,35 @@
+The files in this project were generated using gradle wrapper command.
+`gradle wrapper`
+
+To test, download this project on your machine and run the following:
+`./wrapper tasks`
+
+This should generate output similar to:
+```
+> Task :tasks
+
+------------------------------------------------------------
+Tasks runnable from root project
+------------------------------------------------------------
+
+Build Setup tasks
+-----------------
+init - Initializes a new Gradle build.
+wrapper - Generates Gradle wrapper files.
+
+Help tasks
+----------
+buildEnvironment - Displays all buildscript dependencies declared in root project 'gradle-wrapper'.
+components - Displays the components produced by root project 'gradle-wrapper'. [incubating]
+dependencies - Displays all dependencies declared in root project 'gradle-wrapper'.
+dependencyInsight - Displays the insight into a specific dependency in root project 'gradle-wrapper'.
+dependentComponents - Displays the dependent components of components in root project 'gradle-wrapper'. [incubating]
+help - Displays a help message.
+model - Displays the configuration model of root project 'gradle-wrapper'. [incubating]
+outgoingVariants - Displays the outgoing variants of root project 'gradle-wrapper'.
+projects - Displays the sub-projects of root project 'gradle-wrapper'.
+properties - Displays the properties of root project 'gradle-wrapper'.
+tasks - Displays the tasks runnable from root project 'gradle-wrapper'.
+
+To see all tasks and more detail, run gradlew tasks --all
+```

gradle/gradle-wrapper/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.3-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

gradle/gradle-wrapper/gradlew

@@ -0,0 +1,183 @@
+#!/usr/bin/env sh
+
+#
+# Copyright 2015 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if [ "$cygwin" = "true" -o "$msys" = "true" ] ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=`expr $i + 1`
+    done
+    case $i in
+        0) set -- ;;
+        1) set -- "$args0" ;;
+        2) set -- "$args0" "$args1" ;;
+        3) set -- "$args0" "$args1" "$args2" ;;
+        4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=`save "$@"`
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+exec "$JAVACMD" "$@"

gradle/gradle-wrapper/gradlew.bat

@@ -0,0 +1,103 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto init
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto init
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:init
+@rem Get command-line arguments, handling Windows variants
+
+if not "%OS%" == "Windows_NT" goto win9xME_args
+
+:win9xME_args
+@rem Slurp the command line arguments.
+set CMD_LINE_ARGS=
+set _SKIP=2
+
+:win9xME_args_slurp
+if "x%~1" == "x" goto execute
+
+set CMD_LINE_ARGS=%*
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

hazelcast/pom.xml

@@ -15,7 +15,6 @@
     </parent>
 
     <dependencies>
-        <!-- Hazelcast Jet -->
         <dependency>
             <groupId>com.hazelcast.jet</groupId>
             <artifactId>hazelcast-jet</artifactId>
@@ -34,8 +33,7 @@
     </build>
 
     <properties>
-        <!-- hazelcast jet -->
-        <hazelcast.jet.version>0.6</hazelcast.jet.version>
+        <hazelcast.jet.version>4.2</hazelcast.jet.version>
     </properties>
 
 </project>

hazelcast/src/main/java/com/baeldung/hazelcast/cluster/NativeClient.java

@@ -1,24 +1,20 @@
 package com.baeldung.hazelcast.cluster;
 
-import java.util.Map.Entry;
-
 import com.hazelcast.client.HazelcastClient;
 import com.hazelcast.client.config.ClientConfig;
-import com.hazelcast.config.GroupConfig;
 import com.hazelcast.core.HazelcastInstance;
-import com.hazelcast.core.IMap;
+
+import java.util.Map;
 
 public class NativeClient {
 
-    public static void main(String[] args) throws InterruptedException {
+    public static void main(String[] args) {
         ClientConfig config = new ClientConfig();
-        GroupConfig groupConfig = config.getGroupConfig();
-        groupConfig.setName("dev");
-        groupConfig.setPassword("dev-pass");
+        config.setClusterName("dev");
         HazelcastInstance hazelcastInstanceClient = HazelcastClient.newHazelcastClient(config);
-        IMap<Long, String> map = hazelcastInstanceClient.getMap("data");
-        for (Entry<Long, String> entry : map.entrySet()) {
-            System.out.println(String.format("Key: %d, Value: %s", entry.getKey(), entry.getValue()));
+        Map<Long, String> map = hazelcastInstanceClient.getMap("data");
+        for (Map.Entry<Long, String> entry : map.entrySet()) {
+            System.out.printf("Key: %d, Value: %s%n", entry.getKey(), entry.getValue());
         }
     }
 }

hazelcast/src/main/java/com/baeldung/hazelcast/cluster/ServerNode.java

@@ -1,19 +1,19 @@
 package com.baeldung.hazelcast.cluster;
 
-import java.util.Map;
-
 import com.hazelcast.core.Hazelcast;
 import com.hazelcast.core.HazelcastInstance;
-import com.hazelcast.core.IdGenerator;
+import com.hazelcast.flakeidgen.FlakeIdGenerator;
+
+import java.util.Map;
 
 public class ServerNode {
 
     public static void main(String[] args) {
         HazelcastInstance hazelcastInstance = Hazelcast.newHazelcastInstance();
         Map<Long, String> map = hazelcastInstance.getMap("data");
-        IdGenerator idGenerator = hazelcastInstance.getIdGenerator("newid");
+        FlakeIdGenerator idGenerator = hazelcastInstance.getFlakeIdGenerator("newid");
         for (int i = 0; i < 10; i++) {
-            map.put(idGenerator.newId(), "message" + 1);
+            map.put(idGenerator.newId(), "message" + i);
         }
     }
 }

hazelcast/src/main/java/com/baeldung/hazelcast/jet/WordCounter.java

@@ -1,33 +1,31 @@
 package com.baeldung.hazelcast.jet;
 
-import java.util.List;
-import java.util.Map;
-
-import static com.hazelcast.jet.Traversers.traverseArray;
-import static com.hazelcast.jet.aggregate.AggregateOperations.counting;
-import static com.hazelcast.jet.function.DistributedFunctions.wholeItem;
-
 import com.hazelcast.jet.Jet;
 import com.hazelcast.jet.JetInstance;
 import com.hazelcast.jet.pipeline.Pipeline;
 import com.hazelcast.jet.pipeline.Sinks;
 import com.hazelcast.jet.pipeline.Sources;
 
+import java.util.List;
+import java.util.Map;
+
+import static com.hazelcast.function.Functions.wholeItem;
+import static com.hazelcast.jet.Traversers.traverseArray;
+import static com.hazelcast.jet.aggregate.AggregateOperations.counting;
+
 public class WordCounter {
 
     private static final String LIST_NAME = "textList";
-
     private static final String MAP_NAME = "countMap";
 
     private Pipeline createPipeLine() {
         Pipeline p = Pipeline.create();
-        p.drawFrom(Sources.<String> list(LIST_NAME))
-            .flatMap(word -> traverseArray(word.toLowerCase()
-                .split("\\W+")))
+        p.readFrom(Sources.<String>list(LIST_NAME))
+            .flatMap(word -> traverseArray(word.toLowerCase().split("\\W+")))
             .filter(word -> !word.isEmpty())
             .groupingKey(wholeItem())
             .aggregate(counting())
-            .drainTo(Sinks.map(MAP_NAME));
+            .writeTo(Sinks.map(MAP_NAME));
         return p;
     }
 
@@ -38,8 +36,7 @@ public class WordCounter {
             List<String> textList = jet.getList(LIST_NAME);
             textList.addAll(sentences);
             Pipeline p = createPipeLine();
-            jet.newJob(p)
-                .join();
+            jet.newJob(p).join();
             Map<String, Long> counts = jet.getMap(MAP_NAME);
             count = counts.get(word);
         } finally {

hazelcast/src/main/resources/hazelcast.xml

@@ -1,12 +1,12 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<hazelcast xsi:schemaLocation="http://www.hazelcast.com/schema/config hazelcast-config-3.7.xsd"
-           xmlns="http://www.hazelcast.com/schema/config"
-           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+<hazelcast xmlns="http://www.hazelcast.com/schema/config"
+           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+           xsi:schemaLocation="http://www.hazelcast.com/schema/config
+                               http://www.hazelcast.com/schema/config/hazelcast-config-4.0.xsd">
     <network>
         <port auto-increment="true" port-count="20">5701</port>
         <join>
-            <multicast enabled="false">
-	        </multicast>
+            <multicast enabled="false"/>
             <tcp-ip enabled="true">
                 <member>machine1</member>
                 <member>localhost</member>

hazelcast/src/test/java/com/baeldung/hazelcast/jet/WordCounterUnitTest.java

@@ -1,11 +1,11 @@
 package com.baeldung.hazelcast.jet;
 
-import static org.junit.Assert.assertTrue;
+import org.junit.Test;
 
 import java.util.ArrayList;
 import java.util.List;
 
-import org.junit.Test;
+import static org.junit.Assert.assertEquals;
 
 public class WordCounterUnitTest {
 
@@ -15,7 +15,7 @@ public class WordCounterUnitTest {
         sentences.add("The first second was alright, but the second second was tough.");
         WordCounter wordCounter = new WordCounter();
         long countSecond = wordCounter.countWord(sentences, "second");
-        assertTrue(countSecond == 3);
+        assertEquals(3, countSecond);
     }
 
 }

httpclient-2/README.md

@@ -0,0 +1,12 @@
+## HttpClient 4.x
+
+This module contains articles about HttpClient 4.x
+
+### The Course
+
+The "REST With Spring" Classes: http://bit.ly/restwithspring
+
+### Relevant Articles: 
+
+- [How to Set TLS Version in Apache HttpClient](https://www.baeldung.com/TODO)
+- More articles: [[<-- prev]](../httpclient)

httpclient-2/pom.xml

@@ -0,0 +1,43 @@
+<?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>httpclient-2</artifactId>
+    <version>0.1-SNAPSHOT</version>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.httpcomponents</groupId>
+            <artifactId>httpclient</artifactId>
+            <version>${httpclient.version}</version>
+            <exclusions>
+                <exclusion>
+                    <artifactId>commons-logging</artifactId>
+                    <groupId>commons-logging</groupId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>httpclient-2</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+        <httpclient.version>4.5.8</httpclient.version>
+    </properties>
+
+</project>

httpclient-2/src/main/java/com/baeldung/tlsversion/ClientTlsVersionExamples.java

@@ -0,0 +1,64 @@
+package com.baeldung.tlsversion;
+
+import javax.net.ssl.SSLSocket;
+
+import org.apache.http.HttpEntity;
+import org.apache.http.client.methods.CloseableHttpResponse;
+import org.apache.http.client.methods.HttpGet;
+import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
+import org.apache.http.impl.client.CloseableHttpClient;
+import org.apache.http.impl.client.HttpClients;
+import org.apache.http.ssl.SSLContexts;
+import org.apache.http.util.EntityUtils;
+
+import java.io.IOException;
+
+public class ClientTlsVersionExamples {
+
+    public static CloseableHttpClient setViaSocketFactory() {
+        SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(
+          SSLContexts.createDefault(),
+          new String[] { "TLSv1.2", "TLSv1.3" },
+          null,
+          SSLConnectionSocketFactory.getDefaultHostnameVerifier());
+
+        return HttpClients.custom().setSSLSocketFactory(sslsf).build();
+    }
+
+    public static CloseableHttpClient setTlsVersionPerConnection() {
+        SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(SSLContexts.createDefault()) {
+
+            @Override
+            protected void prepareSocket(SSLSocket socket) {
+                String hostname = socket.getInetAddress().getHostName();
+                if (hostname.endsWith("internal.system.com")) {
+                    socket.setEnabledProtocols(new String[] { "TLSv1", "TLSv1.1", "TLSv1.2", "TLSv1.3" });
+                } else {
+                    socket.setEnabledProtocols(new String[] { "TLSv1.3" });
+                }
+            }
+        };
+
+        return HttpClients.custom().setSSLSocketFactory(sslsf).build();
+    }
+
+    // To configure the TLS versions for the client, set the https.protocols system property during runtime.
+    // For example: java -Dhttps.protocols=TLSv1.1,TLSv1.2,TLSv1.3 -jar webClient.jar
+    public static CloseableHttpClient setViaSystemProperties() {
+        return HttpClients.createSystem();
+        // Alternatively:
+        // return HttpClients.custom().useSystemProperties().build();
+    }
+
+    public static void main(String[] args) throws IOException {
+        // Alternatively:
+        // CloseableHttpClient httpClient = setTlsVersionPerConnection();
+        // CloseableHttpClient httpClient = setViaSystemProperties();
+        try (CloseableHttpClient httpClient = setViaSocketFactory();
+           CloseableHttpResponse response = httpClient.execute(new HttpGet("https://httpbin.org/"))) {
+
+            HttpEntity entity = response.getEntity();
+            EntityUtils.consume(entity);
+        }
+    }
+}

httpclient/README.md

@@ -18,3 +18,4 @@ The "REST With Spring" Classes: http://bit.ly/restwithspring
 - [Advanced HttpClient Configuration](https://www.baeldung.com/httpclient-advanced-config)
 - [HttpClient 4 – Do Not Follow Redirects](https://www.baeldung.com/httpclient-stop-follow-redirect)
 - [Custom User-Agent in HttpClient 4](https://www.baeldung.com/httpclient-user-agent-header)
+- More articles: [[next -->]](../httpclient-2)

java-collections-conversions-2/README.md

@@ -7,4 +7,5 @@ This module contains articles about conversions among Collection types and array
 - [Array to String Conversions](https://www.baeldung.com/java-array-to-string)
 - [Mapping Lists with ModelMapper](https://www.baeldung.com/java-modelmapper-lists)
 - [Converting List to Map With a Custom Supplier](https://www.baeldung.com/list-to-map-supplier)
+- [Arrays.asList vs new ArrayList(Arrays.asList())](https://www.baeldung.com/java-arrays-aslist-vs-new-arraylist)
 - More articles: [[<-- prev]](../java-collections-conversions)

json-2/pom.xml

@@ -116,4 +116,41 @@
         <moshi.version>1.9.2</moshi.version>
         <commons-lang3.version>3.9</commons-lang3.version>
     </properties>
+    <build>
+    	<pluginManagement>
+    		<plugins>
+    			<!--This plugin's configuration is used to store Eclipse m2e settings only. It has no influence on the Maven build itself.-->
+    			<plugin>
+    				<groupId>org.eclipse.m2e</groupId>
+    				<artifactId>lifecycle-mapping</artifactId>
+    				<version>1.0.0</version>
+    				<configuration>
+    					<lifecycleMappingMetadata>
+    						<pluginExecutions>
+    							<pluginExecution>
+    								<pluginExecutionFilter>
+    									<groupId>
+    										org.apache.maven.plugins
+    									</groupId>
+    									<artifactId>
+    										maven-pmd-plugin
+    									</artifactId>
+    									<versionRange>
+    										[3.13.0,)
+    									</versionRange>
+    									<goals>
+    										<goal>check</goal>
+    									</goals>
+    								</pluginExecutionFilter>
+    								<action>
+    									<ignore></ignore>
+    								</action>
+    							</pluginExecution>
+    						</pluginExecutions>
+    					</lifecycleMappingMetadata>
+    				</configuration>
+    			</plugin>
+    		</plugins>
+    	</pluginManagement>
+    </build>
 </project>

json-2/src/main/java/com/baeldung/jsonoptimization/Customer.java

@@ -0,0 +1,123 @@
+package com.baeldung.jsonoptimization;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Objects;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+public class Customer {
+
+    private long id;
+    private String firstName;
+    private String lastName;
+    private String street;
+    private String postalCode;
+    private String city;
+    private String state;
+    private String phoneNumber;
+    private String email;
+
+    public long getId() {
+        return id;
+    }
+
+    public void setId(long id) {
+        this.id = id;
+    }
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public void setFirstName(String firstName) {
+        this.firstName = firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public void setLastName(String lastName) {
+        this.lastName = lastName;
+    }
+
+    public String getStreet() {
+        return street;
+    }
+
+    public void setStreet(String street) {
+        this.street = street;
+    }
+
+    public String getPostalCode() {
+        return postalCode;
+    }
+
+    public void setPostalCode(String postalCode) {
+        this.postalCode = postalCode;
+    }
+
+    public String getCity() {
+        return city;
+    }
+
+    public void setCity(String city) {
+        this.city = city;
+    }
+
+    public String getState() {
+        return state;
+    }
+
+    public void setState(String state) {
+        this.state = state;
+    }
+
+    public String getPhoneNumber() {
+        return phoneNumber;
+    }
+
+    public void setPhoneNumber(String phoneNumber) {
+        this.phoneNumber = phoneNumber;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(city, email, firstName, id, lastName, phoneNumber, postalCode, state, street);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (!(obj instanceof Customer)) {
+            return false;
+        }
+        Customer other = (Customer) obj;
+        return Objects.equals(city, other.city) && Objects.equals(email, other.email) && Objects.equals(firstName, other.firstName) && id == other.id && Objects.equals(lastName, other.lastName) && Objects.equals(phoneNumber, other.phoneNumber)
+            && Objects.equals(postalCode, other.postalCode) && Objects.equals(state, other.state) && Objects.equals(street, other.street);
+    }
+
+    @Override
+    public String toString() {
+        return "Customer [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", street=" + street + ", postalCode=" + postalCode + ", city=" + city + ", state=" + state + ", phoneNumber=" + phoneNumber + ", email=" + email + "]";
+    }
+
+    public static Customer[] fromMockFile() throws IOException {
+        ObjectMapper objectMapper = new ObjectMapper();
+        InputStream jsonFile = new FileInputStream("src/test/resources/json_optimization_mock_data.json");
+        Customer[] feedback = objectMapper.readValue(jsonFile, Customer[].class);
+        return feedback;
+    }
+}

json-2/src/main/java/com/baeldung/jsonoptimization/CustomerDeserializer.java

@@ -0,0 +1,49 @@
+package com.baeldung.jsonoptimization;
+
+import java.io.IOException;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.ObjectCodec;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.deser.std.StdDeserializer;
+
+public class CustomerDeserializer extends StdDeserializer<Customer> {
+    private static final long serialVersionUID = 1L;
+
+    public CustomerDeserializer() {
+        this(null);
+    }
+
+    public CustomerDeserializer(Class<Customer> t) {
+        super(t);
+    }
+
+    @Override
+    public Customer deserialize(JsonParser parser, DeserializationContext deserializer) throws IOException {
+        Customer feedback = new Customer();
+        ObjectCodec codec = parser.getCodec();
+        JsonNode node = codec.readTree(parser);
+
+        feedback.setId(node.get(0)
+            .asLong());
+        feedback.setFirstName(node.get(1)
+            .asText());
+        feedback.setLastName(node.get(2)
+            .asText());
+        feedback.setStreet(node.get(3)
+            .asText());
+        feedback.setPostalCode(node.get(4)
+            .asText());
+        feedback.setCity(node.get(5)
+            .asText());
+        feedback.setState(node.get(6)
+            .asText());
+        JsonNode phoneNumber = node.get(7);
+        feedback.setPhoneNumber(phoneNumber.isNull() ? null : phoneNumber.asText());
+        JsonNode email = node.get(8);
+        feedback.setEmail(email.isNull() ? null : email.asText());
+
+        return feedback;
+    }
+}

json-2/src/main/java/com/baeldung/jsonoptimization/CustomerSerializer.java

@@ -0,0 +1,34 @@
+package com.baeldung.jsonoptimization;
+
+import java.io.IOException;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.SerializerProvider;
+import com.fasterxml.jackson.databind.ser.std.StdSerializer;
+
+public class CustomerSerializer extends StdSerializer<Customer> {
+    private static final long serialVersionUID = 1L;
+
+    public CustomerSerializer() {
+        this(null);
+    }
+
+    public CustomerSerializer(Class<Customer> t) {
+        super(t);
+    }
+
+    @Override
+    public void serialize(Customer customer, JsonGenerator jsonGenerator, SerializerProvider serializer) throws IOException {
+        jsonGenerator.writeStartArray();
+        jsonGenerator.writeNumber(customer.getId());
+        jsonGenerator.writeString(customer.getFirstName());
+        jsonGenerator.writeString(customer.getLastName());
+        jsonGenerator.writeString(customer.getStreet());
+        jsonGenerator.writeString(customer.getPostalCode());
+        jsonGenerator.writeString(customer.getCity());
+        jsonGenerator.writeString(customer.getState());
+        jsonGenerator.writeString(customer.getPhoneNumber());
+        jsonGenerator.writeString(customer.getEmail());
+        jsonGenerator.writeEndArray();
+    }
+}

json-2/src/main/java/com/baeldung/jsonoptimization/CustomerShortNames.java

@@ -0,0 +1,155 @@
+package com.baeldung.jsonoptimization;
+
+import java.util.Objects;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+public class CustomerShortNames {
+
+    @JsonProperty("i")
+    private long id;
+
+    @JsonProperty("f")
+    private String firstName;
+
+    @JsonProperty("l")
+    private String lastName;
+
+    @JsonProperty("s")
+    private String street;
+
+    @JsonProperty("p")
+    private String postalCode;
+
+    @JsonProperty("c")
+    private String city;
+
+    @JsonProperty("a")
+    private String state;
+
+    @JsonProperty("o")
+    private String phoneNumber;
+
+    @JsonProperty("e")
+    private String email;
+
+    public long getId() {
+        return id;
+    }
+
+    public void setId(long id) {
+        this.id = id;
+    }
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public void setFirstName(String firstName) {
+        this.firstName = firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public void setLastName(String lastName) {
+        this.lastName = lastName;
+    }
+
+    public String getStreet() {
+        return street;
+    }
+
+    public void setStreet(String street) {
+        this.street = street;
+    }
+
+    public String getPostalCode() {
+        return postalCode;
+    }
+
+    public void setPostalCode(String postalCode) {
+        this.postalCode = postalCode;
+    }
+
+    public String getCity() {
+        return city;
+    }
+
+    public void setCity(String city) {
+        this.city = city;
+    }
+
+    public String getState() {
+        return state;
+    }
+
+    public void setState(String state) {
+        this.state = state;
+    }
+
+    public String getPhoneNumber() {
+        return phoneNumber;
+    }
+
+    public void setPhoneNumber(String phoneNumber) {
+        this.phoneNumber = phoneNumber;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(city, email, firstName, id, lastName, phoneNumber, postalCode, state, street);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (!(obj instanceof CustomerShortNames)) {
+            return false;
+        }
+        CustomerShortNames other = (CustomerShortNames) obj;
+        return Objects.equals(city, other.city) && Objects.equals(email, other.email) && Objects.equals(firstName, other.firstName) && id == other.id && Objects.equals(lastName, other.lastName) && Objects.equals(phoneNumber, other.phoneNumber)
+            && Objects.equals(postalCode, other.postalCode) && Objects.equals(state, other.state) && Objects.equals(street, other.street);
+    }
+
+    @Override
+    public String toString() {
+        return "CustomerWithShorterAttributes [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", street=" + street + ", postalCode=" + postalCode + ", city=" + city + ", state=" + state + ", phoneNumber=" + phoneNumber + ", email=" + email
+            + "]";
+    }
+
+    public static CustomerShortNames[] fromCustomers(Customer[] customers) {
+        CustomerShortNames[] feedback = new CustomerShortNames[customers.length];
+
+        for (int i = 0; i < customers.length; i++) {
+            Customer aCustomer = customers[i];
+            CustomerShortNames newOne = new CustomerShortNames();
+
+            newOne.setId(aCustomer.getId());
+            newOne.setFirstName(aCustomer.getFirstName());
+            newOne.setLastName(aCustomer.getLastName());
+            newOne.setStreet(aCustomer.getStreet());
+            newOne.setCity(aCustomer.getCity());
+            newOne.setPostalCode(aCustomer.getPostalCode());
+            newOne.setState(aCustomer.getState());
+            newOne.setPhoneNumber(aCustomer.getPhoneNumber());
+            newOne.setEmail(aCustomer.getEmail());
+
+            feedback[i] = newOne;
+        }
+
+        return feedback;
+    }
+
+}

json-2/src/main/java/com/baeldung/jsonoptimization/CustomerSlim.java

@@ -0,0 +1,73 @@
+package com.baeldung.jsonoptimization;
+
+import java.util.Objects;
+
+public class CustomerSlim {
+    private long id;
+    private String name;
+    private String address;
+
+    public long getId() {
+        return id;
+    }
+
+    public void setId(long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getAddress() {
+        return address;
+    }
+
+    public void setAddress(String address) {
+        this.address = address;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(address, id, name);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (!(obj instanceof CustomerSlim)) {
+            return false;
+        }
+        CustomerSlim other = (CustomerSlim) obj;
+        return Objects.equals(address, other.address) && id == other.id && Objects.equals(name, other.name);
+    }
+
+    @Override
+    public String toString() {
+        return "CustomerSlim [id=" + id + ", name=" + name + ", address=" + address + "]";
+    }
+
+    public static CustomerSlim[] fromCustomers(Customer[] customers) {
+        CustomerSlim[] feedback = new CustomerSlim[customers.length];
+
+        for (int i = 0; i < customers.length; i++) {
+            Customer aCustomer = customers[i];
+            CustomerSlim newOne = new CustomerSlim();
+
+            newOne.setId(aCustomer.getId());
+            newOne.setName(aCustomer.getFirstName() + " " + aCustomer.getLastName());
+            newOne.setAddress(aCustomer.getStreet() + ", " + aCustomer.getCity() + " " + aCustomer.getState() + " " + aCustomer.getPostalCode());
+
+            feedback[i] = newOne;
+        }
+
+        return feedback;
+    }
+
+}

json-2/src/main/java/com/baeldung/jsonoptimization/CustomerSlimDeserializer.java

@@ -0,0 +1,37 @@
+package com.baeldung.jsonoptimization;
+
+import java.io.IOException;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.ObjectCodec;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.deser.std.StdDeserializer;
+
+public class CustomerSlimDeserializer extends StdDeserializer<CustomerSlim> {
+    private static final long serialVersionUID = 1L;
+
+    public CustomerSlimDeserializer() {
+        this(null);
+    }
+
+    public CustomerSlimDeserializer(Class<CustomerSlim> t) {
+        super(t);
+    }
+
+    @Override
+    public CustomerSlim deserialize(JsonParser parser, DeserializationContext deserializer) throws IOException {
+        CustomerSlim feedback = new CustomerSlim();
+        ObjectCodec codec = parser.getCodec();
+        JsonNode node = codec.readTree(parser);
+
+        feedback.setId(node.get(0)
+            .asLong());
+        feedback.setName(node.get(1)
+            .asText());
+        feedback.setAddress(node.get(2)
+            .asText());
+
+        return feedback;
+    }
+}

json-2/src/main/java/com/baeldung/jsonoptimization/CustomerSlimSerializer.java

@@ -0,0 +1,28 @@
+package com.baeldung.jsonoptimization;
+
+import java.io.IOException;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.SerializerProvider;
+import com.fasterxml.jackson.databind.ser.std.StdSerializer;
+
+public class CustomerSlimSerializer extends StdSerializer<CustomerSlim> {
+    private static final long serialVersionUID = 1L;
+
+    public CustomerSlimSerializer() {
+        this(null);
+    }
+
+    public CustomerSlimSerializer(Class<CustomerSlim> t) {
+        super(t);
+    }
+
+    @Override
+    public void serialize(CustomerSlim customer, JsonGenerator jsonGenerator, SerializerProvider serializer) throws IOException {
+        jsonGenerator.writeStartArray();
+        jsonGenerator.writeNumber(customer.getId());
+        jsonGenerator.writeString(customer.getName());
+        jsonGenerator.writeString(customer.getAddress());
+        jsonGenerator.writeEndArray();
+    }
+}

json-2/src/main/java/com/baeldung/jsonoptimization/CustomerSlimShortNames.java

@@ -0,0 +1,81 @@
+package com.baeldung.jsonoptimization;
+
+import java.util.Objects;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+public class CustomerSlimShortNames {
+
+    @JsonProperty("i")
+    private long id;
+
+    @JsonProperty("n")
+    private String name;
+
+    @JsonProperty("a")
+    private String address;
+
+    public long getId() {
+        return id;
+    }
+
+    public void setId(long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getAddress() {
+        return address;
+    }
+
+    public void setAddress(String address) {
+        this.address = address;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(address, id, name);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (!(obj instanceof CustomerSlimShortNames)) {
+            return false;
+        }
+        CustomerSlimShortNames other = (CustomerSlimShortNames) obj;
+        return Objects.equals(address, other.address) && id == other.id && Objects.equals(name, other.name);
+    }
+
+    @Override
+    public String toString() {
+        return "CustomerSlim [id=" + id + ", name=" + name + ", address=" + address + "]";
+    }
+
+    public static CustomerSlimShortNames[] fromCustomers(Customer[] customers) {
+        CustomerSlimShortNames[] feedback = new CustomerSlimShortNames[customers.length];
+
+        for (int i = 0; i < customers.length; i++) {
+            Customer aCustomer = customers[i];
+            CustomerSlimShortNames newOne = new CustomerSlimShortNames();
+
+            newOne.setId(aCustomer.getId());
+            newOne.setName(aCustomer.getFirstName() + " " + aCustomer.getLastName());
+            newOne.setAddress(aCustomer.getStreet() + ", " + aCustomer.getCity() + " " + aCustomer.getState() + " " + aCustomer.getPostalCode());
+
+            feedback[i] = newOne;
+        }
+
+        return feedback;
+    }
+
+}

json-2/src/test/java/com/baeldung/jsonoptimization/JsonOptimizationUnitTest.java

@@ -0,0 +1,180 @@
+package com.baeldung.jsonoptimization;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.text.DecimalFormat;
+import java.util.zip.GZIPOutputStream;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import com.fasterxml.jackson.annotation.JsonInclude.Include;
+import com.fasterxml.jackson.core.Version;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.ObjectWriter;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+
+class JsonOptimizationUnitTest {
+    private static final String TEST_LABEL_JACKSON_DEFAULT_OPTIONS = "Default JSON";
+    private static final String TEST_LABEL_DEFAULT_JSON_NO_NULL = "Default JSON without null";
+    private static final String TEST_LABEL_SHORTER_FIELD_NAMES = "Shorter field names";
+    private static final String TEST_LABEL_SHORTER_FIELD_NAMES_AND_NO_NULL = "Shorter field names without null";
+    private static final String TEST_LABEL_SERIALIZING_TO_ARRAY = "Custom serializer";
+    private static final String TEST_LABEL_SLIM_CUSTOM_SERIALIZER = "Slim custom serializer";
+    private static final String TEST_LABEL_SLIM_CUSTOMER = "Slim customer";
+    private static final String TEST_LABEL_SLIM_CUSTOMER_SHORT_NAMES = "Slim customer with shorter field names";
+    private static DecimalFormat LENGTH_FORMATTER = new DecimalFormat("###,###.0");
+    private static DecimalFormat PERCENT_FORMATTER = new DecimalFormat("###.0");
+    private static Customer[] customers;
+    private ObjectMapper mapper;
+    private static int defaultJsonLength;
+
+    @BeforeAll
+    static void setUpOnce() throws Exception {
+        customers = Customer.fromMockFile();
+        ObjectMapper oneTimeMapper = new ObjectMapper();
+        byte[] feedback = oneTimeMapper.writeValueAsBytes(customers);
+        defaultJsonLength = feedback.length;
+        System.out.println();        
+        System.out.println("Default JSON length: " + defaultJsonLength);        
+        System.out.println();        
+    }
+
+    @BeforeEach
+    void setUp() {
+        mapper = new ObjectMapper();
+    }
+
+    @Test
+    void whenSetUp_ThenOneThousandCustomers() {
+        assertEquals(1000, customers.length, "There should be a 1000 customers");
+    }
+
+    @Test
+    void whenJacksonDefaultOptions_thenValid() throws IOException {
+        printBanner(TEST_LABEL_JACKSON_DEFAULT_OPTIONS);
+        byte[] plainJson = createJsonAndVerify(TEST_LABEL_JACKSON_DEFAULT_OPTIONS, customers);
+        compressJson(TEST_LABEL_JACKSON_DEFAULT_OPTIONS, plainJson);
+    }
+
+    @Test
+    void whenExcludingNull_thenValid() throws IOException {
+        printBanner(TEST_LABEL_DEFAULT_JSON_NO_NULL);
+        mapper.setSerializationInclusion(Include.NON_NULL);
+        byte[] plainJson = createJsonAndVerify(TEST_LABEL_DEFAULT_JSON_NO_NULL, customers);
+        compressJson(TEST_LABEL_DEFAULT_JSON_NO_NULL, plainJson);
+    }
+
+    @Test
+    void whenShorterFieldNames_thenValid() throws IOException {
+        printBanner(TEST_LABEL_SHORTER_FIELD_NAMES);
+        CustomerShortNames[] shorterOnes = CustomerShortNames.fromCustomers(customers);
+        byte[] shorterJson = createJsonAndVerify(TEST_LABEL_SHORTER_FIELD_NAMES, shorterOnes);
+        compressJson(TEST_LABEL_SHORTER_FIELD_NAMES, shorterJson);
+    }
+
+    @Test
+    void whenShorterFieldNamesAndExcludingNull_thenValid() throws IOException {
+        printBanner(TEST_LABEL_SHORTER_FIELD_NAMES_AND_NO_NULL);
+        CustomerShortNames[] shorterOnes = CustomerShortNames.fromCustomers(customers);
+        mapper.setSerializationInclusion(Include.NON_NULL);
+        byte[] shorterJson = createJsonAndVerify(TEST_LABEL_SHORTER_FIELD_NAMES_AND_NO_NULL, shorterOnes);
+        compressJson(TEST_LABEL_SHORTER_FIELD_NAMES_AND_NO_NULL, shorterJson);
+    }
+
+    @Test
+    void whenSlimCustomer_thenValid() throws IOException {
+        printBanner(TEST_LABEL_SLIM_CUSTOMER);
+        CustomerSlim[] slimOnes = CustomerSlim.fromCustomers(customers);
+        byte[] slimJson = createJsonAndVerify(TEST_LABEL_SLIM_CUSTOMER, slimOnes);
+        compressJson(TEST_LABEL_SLIM_CUSTOMER, slimJson);
+    }
+
+    @Test
+    void whenSlimCustomerAndShorterFieldNames_thenValid() throws IOException {
+        printBanner(TEST_LABEL_SLIM_CUSTOMER_SHORT_NAMES);
+        CustomerSlimShortNames[] slimOnes = CustomerSlimShortNames.fromCustomers(customers);
+        byte[] slimJson = createJsonAndVerify(TEST_LABEL_SLIM_CUSTOMER_SHORT_NAMES, slimOnes);
+        compressJson(TEST_LABEL_SLIM_CUSTOMER_SHORT_NAMES, slimJson);
+    }
+
+    @Test
+    void whenSerializingToArray_thenValid() throws IOException {
+        printBanner(TEST_LABEL_SERIALIZING_TO_ARRAY);
+        SimpleModule serializer = new SimpleModule("CustomDeSerializer", new Version(1, 0, 0, null, null, null));
+        serializer.addSerializer(Customer.class, new CustomerSerializer());
+        serializer.addDeserializer(Customer.class, new CustomerDeserializer());
+        mapper.registerModule(serializer);
+
+        byte[] plainJson = createJsonAndVerify(TEST_LABEL_SERIALIZING_TO_ARRAY, customers);
+        compressJson(TEST_LABEL_SERIALIZING_TO_ARRAY, plainJson);
+    }
+
+    @Test
+    void whenSerializingToArrayAndSlimCustomer_thenValid() throws IOException {
+        printBanner(TEST_LABEL_SLIM_CUSTOM_SERIALIZER);
+        SimpleModule serializer = new SimpleModule("SlimCustomDeSerializer", new Version(1, 0, 0, null, null, null));
+        serializer.addSerializer(CustomerSlim.class, new CustomerSlimSerializer());
+        serializer.addDeserializer(CustomerSlim.class, new CustomerSlimDeserializer());
+        mapper.registerModule(serializer);
+
+        CustomerSlim[] slimOnes = CustomerSlim.fromCustomers(customers);
+        byte[] plainJson = createJsonAndVerify(TEST_LABEL_SLIM_CUSTOM_SERIALIZER, slimOnes);
+        compressJson(TEST_LABEL_SLIM_CUSTOM_SERIALIZER, plainJson);
+    }
+
+    private void printBanner(String name) {
+        System.out.println();
+        System.out.println("************************************************");
+        System.out.println("Testing " + name);
+        System.out.println();
+    }
+
+    void compressJson(String label, byte[] plainJson) throws IOException {
+        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+        GZIPOutputStream gzipStream = new GZIPOutputStream(outputStream);
+        gzipStream.write(plainJson);
+        gzipStream.close();
+        outputStream.close();
+        byte[] gzippedJson = outputStream.toByteArray();
+        double length = gzippedJson.length / 1024d;
+        double percent = gzippedJson.length * 100d / defaultJsonLength;
+        System.out.println(label + " GZIPped length: " + LENGTH_FORMATTER.format(length) 
+        + "kB (" + PERCENT_FORMATTER.format(percent) + "%)");
+        assertTrue(plainJson.length > gzippedJson.length, label + " should be longer than GZIPped data");
+    }
+
+    private byte[] createJsonAndVerify(String label, Object[] customers) throws IOException {
+        System.out.println(label + " sample: ");
+        ObjectWriter prettyWritter = mapper.writerWithDefaultPrettyPrinter();
+        System.out.println(prettyWritter.writeValueAsString(customers[0]));
+
+        byte[] feedback = mapper.writeValueAsBytes(customers);
+        double length = feedback.length / 1024d;
+        double percent = feedback.length * 100d / defaultJsonLength;
+        System.out.println(label + " length:         " + LENGTH_FORMATTER.format(length) 
+        + "kB (" + PERCENT_FORMATTER.format(percent) + "%)");
+        assertTrue(feedback.length > 1, label + " should be there");
+
+        String prefix = label.replaceAll(" ", "-")
+            .toLowerCase();
+        File tempFile = File.createTempFile("jon-optimization-" + prefix, ".json");
+        FileOutputStream fos = new FileOutputStream(tempFile);
+        fos.write(feedback);
+        fos.close();
+        System.out.println(label + " file:           " + tempFile.toString());
+
+        Object[] restoredOnes = mapper.readValue(feedback, customers.getClass());
+        assertArrayEquals(TEST_LABEL_JACKSON_DEFAULT_OPTIONS + ": restoring from JSON should work", customers, restoredOnes);
+
+        return feedback;
+    }
+
+}

json/README.md

@@ -13,3 +13,4 @@ This module contains articles about JSON.
 - [Get a Value by Key in a JSONArray](https://www.baeldung.com/java-jsonarray-get-value-by-key)
 - [Iterating Over an Instance of org.json.JSONObject](https://www.baeldung.com/jsonobject-iteration)
 - [Escape JSON String in Java](https://www.baeldung.com/java-json-escaping)
+- [Reducing JSON Data Size](https://www.baeldung.com/json-reduce-data-size)

libraries-security/README.md

@@ -11,3 +11,4 @@ This module contains articles about security libraries.
 - [Intro to Jasypt](https://www.baeldung.com/jasypt)
 - [Digital Signatures in Java](https://www.baeldung.com/java-digital-signature)
 - [How to Read PEM File to Get Public and Private Keys](https://www.baeldung.com/java-read-pem-file-keys)
+- [SSH Connection With Java](https://www.baeldung.com/java-ssh-connection)

libraries-testing/README.md

@@ -12,3 +12,4 @@ This module contains articles about test libraries.
 - [Introduction to Hoverfly in Java](https://www.baeldung.com/hoverfly)
 - [Testing with Hamcrest](https://www.baeldung.com/java-junit-hamcrest-guide)
 - [Introduction To DBUnit](https://www.baeldung.com/java-dbunit)
+- [Introduction to ArchUnit](https://www.baeldung.com/java-archunit-intro)

lombok/src/main/java/com/baeldung/lombok/builder/RequiredFieldAnnotation.java

@@ -0,0 +1,18 @@
+package com.baeldung.lombok.builder;
+
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NonNull;
+
+@Builder(builderMethodName = "internalBuilder")
+@Getter
+public class RequiredFieldAnnotation {
+
+    @NonNull
+    String name;
+    String description;
+
+    public static RequiredFieldAnnotationBuilder builder(String name) {
+        return internalBuilder().name(name);
+    }
+}

lombok/src/test/java/com/baeldung/lombok/builder/RequiredFieldAnnotationUnitTest.java

@@ -0,0 +1,21 @@
+package com.baeldung.lombok.builder;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class RequiredFieldAnnotationUnitTest {
+    RequiredFieldAnnotation requiredFieldTest;
+
+    @Before
+    public void setUp() {
+        requiredFieldTest = RequiredFieldAnnotation.builder("NameField").description("Field Description").build();
+    }
+
+    @Test
+    public void givenBuilderWithRequiredParameter_thenParameterIsPresent() {
+        assertEquals("NameField", requiredFieldTest.getName());
+    }
+
+}

mapstruct/pom.xml

@@ -71,7 +71,7 @@
     </build>
 
     <properties>
-        <org.mapstruct.version>1.4.0.Beta1</org.mapstruct.version>
+        <org.mapstruct.version>1.3.1.Final</org.mapstruct.version>
         <springframework.version>4.3.4.RELEASE</springframework.version>
         <maven.compiler.source>1.8</maven.compiler.source>
         <maven.compiler.target>1.8</maven.compiler.target>

mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/CompanyMapperAdderPreferred.java

@@ -5,7 +5,8 @@ import com.baeldung.mapstruct.mappingCollections.model.Company;
 import org.mapstruct.CollectionMappingStrategy;
 import org.mapstruct.Mapper;
 
-@Mapper(collectionMappingStrategy = CollectionMappingStrategy.ADDER_PREFERRED)
+@Mapper(collectionMappingStrategy = CollectionMappingStrategy.ADDER_PREFERRED,
+        uses = EmployeeMapper.class)
 public interface CompanyMapperAdderPreferred {
 
     CompanyDTO map(Company company);

mapstruct/src/main/java/com/baeldung/mapstruct/mappingCollections/mapper/EmployeeMapper.java

@@ -11,6 +11,8 @@ import java.util.Set;
 @Mapper
 public interface EmployeeMapper {
 
+    EmployeeDTO map(Employee employee);
+
     List<EmployeeDTO> map(List<Employee> employees);
 
     Set<EmployeeDTO> map(Set<Employee> employees);

maven-java-11/multimodule-maven-project/entitymodule/pom.xml

@@ -1,22 +0,0 @@
-<?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.entitymodule</groupId>
-    <artifactId>entitymodule</artifactId>
-    <version>1.0</version>
-    <name>entitymodule</name>
-    <packaging>jar</packaging>
-
-    <parent>
-        <groupId>com.baeldung.multimodule-maven-project</groupId>
-        <artifactId>multimodule-maven-project</artifactId>
-        <version>1.0</version>
-    </parent>
-
-    <properties>
-        <maven.compiler.source>11</maven.compiler.source>
-        <maven.compiler.target>11</maven.compiler.target>
-    </properties>
-
-</project>

maven-java-11/multimodule-maven-project/entitymodule/src/main/java/com/baeldung/entity/User.java

@@ -1,19 +0,0 @@
-package com.baeldung.entity;
-
-public class User {
-
-    private final String name;
-
-    public User(String name) {
-        this.name = name;
-    }
-
-    public String getName() {
-        return name;
-    }
-
-    @Override
-    public String toString() {
-        return "User{" + "name=" + name + '}';
-    }
-}

maven-java-11/multimodule-maven-project/entitymodule/src/main/java/module-info.java

@@ -1,3 +0,0 @@
-module com.baeldung.entity {
-    exports com.baeldung.entity;
-}

maven-java-11/multimodule-maven-project/mainappmodule/pom.xml

@@ -1,41 +0,0 @@
-<?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.mainappmodule</groupId>
-    <artifactId>mainappmodule</artifactId>
-    <version>1.0</version>
-    <name>mainappmodule</name>
-    <packaging>jar</packaging>
-
-    <parent>
-        <groupId>com.baeldung.multimodule-maven-project</groupId>
-        <artifactId>multimodule-maven-project</artifactId>
-        <version>1.0</version>
-    </parent>
-
-    <dependencies>
-        <dependency>
-            <groupId>com.baeldung.entitymodule</groupId>
-            <artifactId>entitymodule</artifactId>
-            <version>${entitymodule.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.baeldung.daomodule</groupId>
-            <artifactId>daomodule</artifactId>
-            <version>${daomodule.version}</version>
-        </dependency>
-        <dependency>
-            <groupId>com.baeldung.userdaomodule</groupId>
-            <artifactId>userdaomodule</artifactId>
-            <version>${userdaomodule.version}</version>
-        </dependency>
-    </dependencies>
-
-    <properties>
-        <entitymodule.version>1.0</entitymodule.version>
-        <daomodule.version>1.0</daomodule.version>
-        <userdaomodule.version>1.0</userdaomodule.version>
-    </properties>
-
-</project>

maven-java-11/multimodule-maven-project/mainappmodule/src/main/java/com/baeldung/mainapp/Application.java

@@ -1,19 +0,0 @@
-package com.baeldung.mainapp;
-
-import com.baeldung.dao.Dao;
-import com.baeldung.entity.User;
-import com.baeldung.userdao.UserDao;
-import java.util.HashMap;
-import java.util.Map;
-
-public class Application {
-    
-    public static void main(String[] args) {
-        Map<Integer, User> users = new HashMap<>();
-        users.put(1, new User("Julie"));
-        users.put(2, new User("David"));
-        Dao userDao = new UserDao(users);
-        userDao.findAll().forEach(System.out::println);
-    }
-    
-}

maven-java-11/multimodule-maven-project/mainappmodule/src/main/java/module-info.java

@@ -1,6 +0,0 @@
-module com.baeldung.mainapp {
-    requires com.baeldung.entity;
-    requires com.baeldung.userdao;
-    requires com.baeldung.dao;
-    uses com.baeldung.dao.Dao;
-}

maven-modules/maven-plugins/pom.xml

@@ -14,6 +14,11 @@
         <relativePath>../..</relativePath>
     </parent>
 
+    <modules>
+        <!--<module>custom-rule</module>--> <!-- Fixing in JAVA-2819 -->
+        <module>maven-enforcer</module>
+    </modules>
+
     <build>
         <plugins>
             <plugin>

patterns/design-patterns-architectural/README.md

@@ -1,3 +1,4 @@
 ### Relevant Articles:
 - [Service Locator Pattern](https://www.baeldung.com/java-service-locator-pattern)
 - [The DAO Pattern in Java](https://www.baeldung.com/java-dao-pattern)
+- [DAO vs Repository Patterns](https://www.baeldung.com/java-dao-vs-repository)

persistence-modules/apache-bookkeeper/pom.xml

@@ -11,9 +11,8 @@
 
     <parent>
         <groupId>com.baeldung</groupId>
-        <artifactId>parent-modules</artifactId>
+        <artifactId>persistence-modules</artifactId>
         <version>1.0.0-SNAPSHOT</version>
-        <relativePath>../../</relativePath>
     </parent>
 
     <dependencies>

persistence-modules/deltaspike/pom.xml

@@ -188,13 +188,6 @@
             <scope>provided</scope>
         </dependency>
 
-        <!-- Needed for running tests (you may also use TestNG) -->
-        <dependency>
-            <groupId>junit</groupId>
-            <artifactId>junit</artifactId>
-            <scope>test</scope>
-        </dependency>
-
         <!-- Others -->
         <dependency>
             <groupId>org.apache.commons</groupId>

persistence-modules/flyway-repair/pom.xml

@@ -75,6 +75,11 @@
 
     <properties>
         <flyway.configFiles>src/main/resources/application-${spring-boot.run.profiles}.properties</flyway.configFiles>
+
+        <!-- testing -->
+        <maven-surefire-plugin.version>2.22.2</maven-surefire-plugin.version>
+        <junit-jupiter.version>5.6.2</junit-jupiter.version>
+        <junit.version>4.13</junit.version>
     </properties>
 
 </project>

persistence-modules/flyway/README.md

@@ -1,3 +1,4 @@
 ### Relevant Articles:
 - [Database Migrations with Flyway](http://www.baeldung.com/database-migrations-with-flyway)
 - [A Guide to Flyway Callbacks](http://www.baeldung.com/flyway-callbacks)
+- [Rolling Back Migrations with Flyway](https://www.baeldung.com/flyway-roll-back)

persistence-modules/flyway/pom.xml

@@ -65,6 +65,11 @@
     <properties>
         <flyway-core.version>5.2.3</flyway-core.version>
         <flyway-maven-plugin.version>5.0.2</flyway-maven-plugin.version>
+
+        <!-- testing -->
+        <maven-surefire-plugin.version>2.22.2</maven-surefire-plugin.version>
+        <junit-jupiter.version>5.6.2</junit-jupiter.version>
+        <junit.version>4.13</junit.version>
     </properties>
 
 </project>

persistence-modules/jooq/pom.xml

@@ -0,0 +1,46 @@
+<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>jooq</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>jooq-examples</name>
+    <packaging>jar</packaging>
+    <description>jOOQ Examples</description>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>persistence-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.jooq</groupId>
+            <artifactId>jooq</artifactId>
+            <version>3.13.4</version>
+        </dependency>
+        <dependency>
+            <groupId>org.jooq</groupId>
+            <artifactId>jooq-meta</artifactId>
+            <version>3.13.4</version>
+        </dependency>
+        <dependency>
+            <groupId>org.jooq</groupId>
+            <artifactId>jooq-codegen</artifactId>
+            <version>3.13.4</version>
+        </dependency>
+        <dependency>
+            <groupId>org.postgresql</groupId>
+            <artifactId>postgresql</artifactId>
+            <version>42.2.16</version>
+        </dependency>
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <version>1.4.200</version>
+        </dependency>
+    </dependencies>
+
+</project>

persistence-modules/jooq/src/main/java/com/baeldung/jooq/Crud.java

@@ -0,0 +1,57 @@
+package com.baeldung.jooq;
+
+import org.jooq.Condition;
+import org.jooq.DSLContext;
+import org.jooq.Field;
+import org.jooq.Record;
+import org.jooq.Result;
+import org.jooq.SelectFieldOrAsterisk;
+import org.jooq.Table;
+import org.jooq.UpdatableRecord;
+
+import java.util.Map;
+
+public class Crud {
+
+    public static <R extends UpdatableRecord<R>> void save(UpdatableRecord<R> record) {
+        record.store();
+    }
+
+    public static Result<Record> getAll(DSLContext context, Table<? extends Record> table) {
+        return context.select()
+                .from(table)
+                .fetch();
+    }
+
+    public static Result<Record> getFields(DSLContext context, Table<? extends Record> table, SelectFieldOrAsterisk... fields) {
+        return context.select(fields)
+                .from(table)
+                .fetch();
+    }
+
+    public static <R extends Record> R getOne(DSLContext context, Table<R> table, Condition condition) {
+        return context.fetchOne(table, condition);
+    }
+
+    public static <T> void update(DSLContext context, Table<? extends Record> table, Map<Field<T>, T> values, Condition condition) {
+        context.update(table)
+                .set(values)
+                .where(condition)
+                .execute();
+    }
+
+    public static <R extends UpdatableRecord<R>> void update(UpdatableRecord<R> record) {
+        record.update();
+    }
+
+    public static void delete(DSLContext context, Table<? extends Record> table, Condition condition) {
+        context.delete(table)
+                .where(condition)
+                .execute();
+    }
+
+    public static <R extends UpdatableRecord<R>> void delete(UpdatableRecord<R> record) {
+        record.delete();
+    }
+
+}

persistence-modules/jooq/src/main/java/com/baeldung/jooq/CrudExamples.java

@@ -0,0 +1,117 @@
+package com.baeldung.jooq;
+
+import com.baeldung.jooq.model.tables.Article;
+import com.baeldung.jooq.model.tables.Author;
+import com.baeldung.jooq.model.tables.records.ArticleRecord;
+import com.baeldung.jooq.model.tables.records.AuthorRecord;
+import org.jooq.DSLContext;
+import org.jooq.Field;
+import org.jooq.Record;
+import org.jooq.Result;
+import org.jooq.SQLDialect;
+import org.jooq.impl.DSL;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.SQLException;
+import java.util.HashMap;
+
+import static com.baeldung.jooq.Crud.delete;
+import static com.baeldung.jooq.Crud.getAll;
+import static com.baeldung.jooq.Crud.getFields;
+import static com.baeldung.jooq.Crud.getOne;
+import static com.baeldung.jooq.Crud.save;
+import static com.baeldung.jooq.Crud.update;
+
+public class CrudExamples {
+
+    public void crudExamples() throws SQLException {
+        String userName = "username";
+        String password = "password";
+        String url = "jdbc:postgresql://db_url:5432/baeldung_database";
+
+        Connection conn = DriverManager.getConnection(url, userName, password);
+        DSLContext context = DSL.using(conn, SQLDialect.POSTGRES);
+
+        createValues(context);
+        readValues(context);
+        updateValues(context);
+        deleteValues(context);
+    }
+
+    private void createValues(DSLContext context) {
+        ArticleRecord article = context.newRecord(Article.ARTICLE);
+
+        article.setId(2);
+        article.setTitle("jOOQ examples");
+        article.setDescription("A few examples of jOOQ CRUD operations");
+        article.setAuthorId(1);
+
+        save(article);
+
+        AuthorRecord author = context.newRecord(Author.AUTHOR);
+        author.setId(1);
+        author.setFirstName("John");
+        author.setLastName("Smith");
+        author.setAge(40);
+
+        save(author);
+    }
+
+    private void readValues(DSLContext context) {
+        Result<Record> authors = getAll(
+                context,
+                Author.AUTHOR
+        );
+
+        authors.forEach(author -> {
+            Integer id = author.getValue(Author.AUTHOR.ID);
+            String firstName = author.getValue(Author.AUTHOR.FIRST_NAME);
+            String lastName = author.getValue(Author.AUTHOR.LAST_NAME);
+            Integer age = author.getValue(Author.AUTHOR.AGE);
+            System.out.printf("Author %s %s has id: %d and age: %d%n", firstName, lastName, id, age);
+        });
+
+        Result<Record> articles = getFields(
+                context,
+                Author.AUTHOR,
+                Article.ARTICLE.ID, Article.ARTICLE.TITLE
+        );
+
+        AuthorRecord author = getOne(
+                context,
+                Author.AUTHOR,
+                Author.AUTHOR.ID.eq(1)
+        );
+    }
+
+    private void updateValues(DSLContext context) {
+        HashMap<Field<String>, String> fieldsToUpdate = new HashMap<>();
+        fieldsToUpdate.put(Author.AUTHOR.FIRST_NAME, "David");
+        fieldsToUpdate.put(Author.AUTHOR.LAST_NAME, "Brown");
+        update(
+                context,
+                Author.AUTHOR,
+                fieldsToUpdate,
+                Author.AUTHOR.ID.eq(1)
+        );
+
+        ArticleRecord article = context.fetchOne(Article.ARTICLE, Article.ARTICLE.ID.eq(1));
+        article.setTitle("A New Article Title");
+        update(
+                article
+        );
+    }
+
+    private void deleteValues(DSLContext context) {
+        delete(
+                context,
+                Article.ARTICLE,
+                Article.ARTICLE.ID.eq(1)
+        );
+
+        AuthorRecord author = context.fetchOne(Author.AUTHOR, Author.AUTHOR.ID.eq(1));
+        delete(author);
+    }
+
+}

persistence-modules/jooq/src/main/java/com/baeldung/jooq/model/DefaultCatalog.java

@@ -0,0 +1,44 @@
+/*
+ * This file is generated by jOOQ.
+ */
+package com.baeldung.jooq.model;
+
+
+import org.jooq.Schema;
+import org.jooq.impl.CatalogImpl;
+
+import java.util.Arrays;
+import java.util.List;
+
+
+/**
+ * This class is generated by jOOQ.
+ */
+@SuppressWarnings({ "all", "unchecked", "rawtypes" })
+public class DefaultCatalog extends CatalogImpl {
+
+    private static final long serialVersionUID = 1035293962;
+
+    /**
+     * The reference instance of <code>DEFAULT_CATALOG</code>
+     */
+    public static final DefaultCatalog DEFAULT_CATALOG = new DefaultCatalog();
+
+    /**
+     * The schema <code>public</code>.
+     */
+    public final Public PUBLIC = Public.PUBLIC;
+
+    /**
+     * No further instances allowed
+     */
+    private DefaultCatalog() {
+        super("");
+    }
+
+    @Override
+    public final List<Schema> getSchemas() {
+        return Arrays.<Schema>asList(
+            Public.PUBLIC);
+    }
+}