Merge remote-tracking branch 'Baeldung/master' into active_mq

# Conflicts:
#	.gitignore
#	LICENSE
#	README.md
#	core-java-modules/README.md
#	core-java-modules/core-java-11/README.md
#	core-java-modules/core-java-11/pom.xml
#	core-java-modules/core-java-8/README.md
#	core-java-modules/core-java-8/pom.xml
#	core-java-modules/core-java-8/src/main/resources/logback.xml
#	core-java-modules/core-java-annotations/README.md
#	core-java-modules/core-java-annotations/pom.xml
#	core-java-modules/core-java-collections-2/README.md
#	core-java-modules/core-java-collections-2/pom.xml
#	core-java-modules/core-java-collections-3/README.md
#	core-java-modules/core-java-collections-3/pom.xml
#	core-java-modules/core-java-collections-conversions-2/README.md
#	core-java-modules/core-java-collections-conversions-2/pom.xml
#	core-java-modules/core-java-collections-conversions/README.md
#	core-java-modules/core-java-collections-conversions/pom.xml
#	core-java-modules/core-java-collections-list/README.md
#	core-java-modules/core-java-collections-list/pom.xml
#	core-java-modules/core-java-collections/pom.xml
#	core-java-modules/core-java-datetime-conversion/README.md
#	core-java-modules/core-java-datetime-conversion/pom.xml
#	core-java-modules/core-java-datetime-conversion/src/test/java/com/baeldung/datetime/ConvertInstantToTimestampUnitTest.java
#	core-java-modules/core-java-io-2/pom.xml
#	core-java-modules/core-java-io/README.md
#	core-java-modules/core-java-io/pom.xml
#	core-java-modules/core-java-io/src/test/resources/fileTest.txt
#	core-java-modules/core-java-io/src/test/resources/sampleTextFile.txt
#	core-java-modules/core-java-lambdas/README.md
#	core-java-modules/core-java-lambdas/pom.xml
#	core-java-modules/core-java-serialization/pom.xml
#	core-java-modules/core-java-streams/README.md
#	core-java-modules/core-java-streams/pom.xml
#	core-java-modules/core-java-strings/README.md
#	core-java-modules/core-java-strings/pom.xml
#	core-java-modules/core-java-strings/src/test/resources/stringtoolong.txt
#	core-java-modules/core-java-uuid/README.md
#	core-java-modules/core-java-uuid/pom.xml
#	core-java-modules/pom.xml
#	image-processing/README.md
#	image-processing/pom.xml
#	image-processing/src/main/java/com/baeldung/imageprocessing/addingtext/AddText.java
#	image-processing/src/main/java/com/baeldung/imageprocessing/opencv/CameraStream.java
#	jackson-modules/jackson-annotations/README.md
#	jackson-modules/jackson-annotations/pom.xml
#	jackson-modules/jackson-conversions-2/README.md
#	jackson-modules/jackson-conversions-2/pom.xml
#	jackson-modules/jackson-conversions/README.md
#	jackson-modules/jackson-conversions/pom.xml
#	jackson-modules/jackson-custom-conversions/README.md
#	jackson-modules/jackson-custom-conversions/pom.xml
#	jackson-modules/jackson-custom-conversions/src/test/java/com/baeldung/defaultserializercustomserializer/CallingDefaultSerializerUnitTest.java
#	jackson-modules/jackson-custom-conversions/src/test/java/com/baeldung/deserialization/CustomDeserializationUnitTest.java
#	jackson-modules/jackson-exceptions/README.md
#	jackson-modules/jackson-exceptions/pom.xml
#	jackson-modules/jackson-exceptions/src/test/java/com/baeldung/exceptions/JacksonExceptionsUnitTest.java
#	jackson-modules/jackson-exceptions/src/test/java/com/baeldung/mappingexception/JacksonMappingExceptionUnitTest.java
#	jackson-modules/pom.xml
#	parent-boot-1/pom.xml
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#	parent-boot-3/pom.xml
#	patterns-modules/design-patterns-architectural/pom.xml
#	patterns-modules/design-patterns-architectural/src/main/java/com/baeldung/repositoryvsdaopattern/UserDaoImpl.java
#	patterns-modules/design-patterns-behavioral-2/README.md
#	patterns-modules/design-patterns-behavioral-2/pom.xml
#	patterns-modules/design-patterns-creational-2/README.md
#	patterns-modules/design-patterns-creational-2/pom.xml
#	patterns-modules/design-patterns-singleton/README.md
#	patterns-modules/design-patterns-structural/src/main/resources/log4jstructuraldp.properties
#	patterns-modules/enterprise-patterns/pom.xml
#	patterns-modules/intercepting-filter/pom.xml
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#	persistence-modules/activejdbc/pom.xml
#	persistence-modules/hibernate5/README.md
#	persistence-modules/hibernate5/pom.xml
#	persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/interceptors/CustomInterceptor.java
#	persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/interceptors/entity/User.java
#	persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/namingstrategy/CustomPhysicalNamingStrategy.java
#	persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/persistjson/Customer.java
#	persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/persistjson/HashMapConverter.java
#	persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/pojo/OrderEntryIdClass.java
#	persistence-modules/hibernate5/src/main/java/com/baeldung/hibernate/pojo/OrderEntryPK.java
#	persistence-modules/hibernate5/src/test/java/com/baeldung/hibernate/IdentifiersIntegrationTest.java
#	persistence-modules/hibernate5/src/test/java/com/baeldung/hibernate/bootstrap/BootstrapAPIIntegrationTest.java
#	persistence-modules/hibernate5/src/test/java/com/baeldung/hibernate/proxy/HibernateProxyUnitTest.java
#	persistence-modules/hibernate5/src/test/resources/hibernate-interceptors.properties
#	persistence-modules/hibernate5/src/test/resources/hibernate-lifecycle.properties
#	persistence-modules/hibernate5/src/test/resources/hibernate-namingstrategy.properties
#	persistence-modules/hibernate5/src/test/resources/hibernate-persistjson.properties
#	persistence-modules/hibernate5/src/test/resources/hibernate.properties
#	persistence-modules/pom.xml
#	persistence-modules/spring-data-jpa-crud/pom.xml
#	persistence-modules/spring-data-jpa-crud/src/main/java/com/baeldung/repository/FruitRepository.java
#	persistence-modules/spring-data-jpa-repo-2/README.md
#	persistence-modules/spring-data-jpa-repo-2/pom.xml
#	persistence-modules/spring-data-jpa-repo-2/src/main/java/com/baeldung/spring/data/persistence/customrepository/model/User.java
#	persistence-modules/spring-data-jpa-repo-2/src/main/java/com/baeldung/spring/data/persistence/customrepository/repository/CustomUserRepositoryImpl.java
#	persistence-modules/spring-data-jpa-repo-2/src/main/java/com/baeldung/spring/data/persistence/saveperformance/Book.java
#	persistence-modules/spring-data-jpa-repo-2/src/main/resources/application.properties
#	persistence-modules/spring-data-mongodb-reactive/pom.xml
#	persistence-modules/spring-data-redis/README.md
#	persistence-modules/spring-data-redis/pom.xml
#	persistence-modules/spring-data-redis/src/main/java/com/baeldung/spring/data/reactive/redis/config/RedisConfig.java
#	persistence-modules/spring-data-redis/src/main/java/com/baeldung/spring/data/redis/config/RedisConfig.java
#	persistence-modules/spring-data-redis/src/main/java/com/baeldung/spring/data/redis/model/Student.java
#	persistence-modules/spring-data-redis/src/main/java/com/baeldung/spring/data/redis/queue/RedisMessageSubscriber.java
#	persistence-modules/spring-data-redis/src/test/java/com/baeldung/spring/data/reactive/redis/template/RedisKeyCommandsManualTest.java
#	persistence-modules/spring-data-redis/src/test/java/com/baeldung/spring/data/reactive/redis/template/RedisTemplateListOpsManualTest.java
#	persistence-modules/spring-data-redis/src/test/java/com/baeldung/spring/data/reactive/redis/template/RedisTemplateValueOpsManualTest.java
#	persistence-modules/spring-data-redis/src/test/java/com/baeldung/spring/data/redis/repo/StudentRepositoryManualTest.java
#	pom.xml
#	testing-modules/assertion-libraries/README.md
#	testing-modules/assertion-libraries/pom.xml
#	testing-modules/junit-5-basics/README.md
#	testing-modules/junit-5-basics/pom.xml
#	testing-modules/mockito-2/src/main/java/com/baeldung/nullmatcher/Helper.java
#	testing-modules/mockito-2/src/main/java/com/baeldung/nullmatcher/Main.java
#	testing-modules/mockito-2/src/main/java/com/baeldung/wantedbutnotinvocked/Helper.java
#	testing-modules/mockito-2/src/main/java/com/baeldung/wantedbutnotinvocked/Main.java
#	testing-modules/mockito-2/src/test/java/com/baeldung/nullmatcher/MainUnitTest.java
#	testing-modules/mockito-2/src/test/java/com/baeldung/wantedbutnotinvocked/MainUnitTest.java
#	testing-modules/pom.xml
#	testing-modules/spring-mockito/pom.xml
#	web-modules/dropwizard/pom.xml
#	web-modules/jakarta-ee/README.md
#	web-modules/jakarta-ee/pom.xml
#	web-modules/jakarta-ee/src/test/java/com/baeldung/eclipse/krazo/UserControllerUnitTest.java
#	web-modules/java-lite/pom.xml
#	web-modules/javax-servlets-2/README.md
#	web-modules/javax-servlets-2/pom.xml
#	web-modules/javax-servlets/pom.xml
#	web-modules/jee-7/pom.xml
#	web-modules/jooby/pom.xml
#	web-modules/ninja/pom.xml
#	web-modules/pom.xml
#	web-modules/ratpack/pom.xml
#	web-modules/resteasy/pom.xml
#	web-modules/restx/pom.xml
#	web-modules/spark-java/pom.xml
#	web-modules/vraptor/pom.xml
#	xml/README.md
#	xml/pom.xml
#	xml/src/main/resources/customer-binding.xml
#	xml/src/main/resources/sax/baeldung.xml
#	xml/src/test/resources/example_default_parser.xml
#	xml/src/test/resources/example_dom4j.xml
#	xml/src/test/resources/example_jaxb.xml
#	xml/src/test/resources/example_jaxen.xml
#	xml/src/test/resources/example_jdom.xml
#	xml/src/test/resources/example_stax.xml
#	xml/src/test/resources/sax/baeldung.xml
#	xml/src/test/resources/xml/websites.xml
#	xml/src/test/resources/xml/xee_attribute.xml

patterns-modules/design-patterns-behavioral-2/src/main/java/com/baeldung/memento/TextEditor.java

@@ -0,0 +1,27 @@
+package com.baeldung.memento;
+
+public class TextEditor {
+
+    private TextWindow textWindow;
+    private TextWindowState savedTextWindow;
+
+    public TextEditor(TextWindow textWindow) {
+        this.textWindow = textWindow;
+    }
+
+    public void write(String text) {
+        textWindow.addText(text);
+    }
+
+    public String print() {
+        return textWindow.getCurrentText();
+    }
+
+    public void hitSave() {
+        savedTextWindow = textWindow.save();
+    }
+
+    public void hitUndo() {
+        textWindow.restore(savedTextWindow);
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/main/java/com/baeldung/memento/TextWindow.java

@@ -0,0 +1,26 @@
+package com.baeldung.memento;
+
+public class TextWindow {
+
+    private StringBuilder currentText;
+
+    public TextWindow() {
+        this.currentText = new StringBuilder();
+    }
+
+    public String getCurrentText() {
+        return currentText.toString();
+    }
+
+    public void addText(String text) {
+        currentText.append(text);
+    }
+
+    public TextWindowState save() {
+        return new TextWindowState(currentText.toString());
+    }
+
+    public void restore(TextWindowState save) {
+        currentText = new StringBuilder(save.getText());
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/main/java/com/baeldung/memento/TextWindowState.java

@@ -0,0 +1,14 @@
+package com.baeldung.memento;
+
+public class TextWindowState {
+
+    private String text;
+
+    public TextWindowState(String text) {
+        this.text = text;
+    }
+
+    public String getText() {
+        return text;
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/main/java/com/baeldung/nullconversion/Address.java

@@ -0,0 +1,26 @@
+package com.baeldung.nullconversion;
+
+public class Address implements Cloneable {
+
+    private ZipCode zipCode;
+
+    public ZipCode getZipCode() {
+        return zipCode;
+    }
+
+    public void setZipCode(ZipCode zipCode) {
+        this.zipCode = zipCode;
+    }
+
+    @Override
+    protected Address clone()  {
+        Address address;
+        try {
+            address = ((Address) super.clone());
+        } catch (CloneNotSupportedException e) {
+            throw new RuntimeException(e);
+        }
+        zipCode = zipCode.clone();
+        return address;
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/main/java/com/baeldung/nullconversion/Delivery.java

@@ -0,0 +1,38 @@
+package com.baeldung.nullconversion;
+
+import java.util.Objects;
+
+public class Delivery {
+
+    private String message;
+
+    public Delivery(String message) {
+        this.message = message;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+
+        Delivery delivery = (Delivery) o;
+
+        return Objects.equals(message, delivery.message);
+    }
+
+    @Override
+    public int hashCode() {
+        return message != null ? message.hashCode() : 0;
+    }
+
+    public static Delivery freeDelivery() {
+        return new Delivery("Free delivery");
+    }
+    public static Delivery defaultDelivery() {
+        return new Delivery("Default delivery");
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/main/java/com/baeldung/nullconversion/DeliveryService.java

@@ -0,0 +1,6 @@
+package com.baeldung.nullconversion;
+
+public interface DeliveryService {
+
+    Delivery calculateDeliveryForPerson(Long id);
+}

patterns-modules/design-patterns-behavioral-2/src/main/java/com/baeldung/nullconversion/Person.java

@@ -0,0 +1,26 @@
+package com.baeldung.nullconversion;
+
+public class Person implements Cloneable {
+
+    private Address address;
+
+    public Address getAddress() {
+        return address;
+    }
+
+    public void setAddress(Address address) {
+        this.address = address;
+    }
+
+    @Override
+    protected Person clone() {
+        Person person;
+        try {
+            person = (Person) super.clone();
+        } catch (CloneNotSupportedException e) {
+            throw new RuntimeException(e);
+        }
+        address = address.clone();
+        return person;
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/main/java/com/baeldung/nullconversion/ZipCode.java

@@ -0,0 +1,27 @@
+package com.baeldung.nullconversion;
+
+public class ZipCode implements Cloneable {
+
+    private String code;
+
+    public ZipCode(String code) {
+        this.code = code;
+    }
+
+    public String getCode() {
+        return code;
+    }
+
+    @Override
+    protected ZipCode clone() {
+        try {
+            return (ZipCode) super.clone();
+        } catch (CloneNotSupportedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public void setCode(String code) {
+        this.code = code;
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/memento/TextEditorUnitTest.java

@@ -0,0 +1,20 @@
+package com.baeldung.memento;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class TextEditorUnitTest {
+
+    @Test
+    void givenTextEditor_whenAddTextSaveAddMoreAndUndo_thenSavecStateRestored() {
+        TextEditor textEditor = new TextEditor(new TextWindow());
+        textEditor.write("The Memento Design Pattern\n");
+        textEditor.write("How to implement it in Java?\n");
+        textEditor.hitSave();
+        textEditor.write("Buy milk and eggs before coming home\n");
+        textEditor.hitUndo();
+
+        assertThat(textEditor.print()).isEqualTo("The Memento Design Pattern\nHow to implement it in Java?\n");
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/NullConversionUnitTest.java

@@ -0,0 +1,130 @@
+package com.baeldung.nullconversion;
+
+import static java.util.Objects.requireNonNullElse;
+import static java.util.Objects.requireNonNullElseGet;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+
+import com.google.common.base.MoreObjects;
+import java.util.Optional;
+import java.util.function.Supplier;
+import org.apache.commons.lang3.ObjectUtils;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ArgumentsSource;
+
+class NullConversionUnitTest {
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenIfWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = defaultValue;
+        if (givenValue != null) {
+            actual = givenValue;
+        }
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsSupplierProvider.class)
+    void givenIfWhenNotNullThenReturnsDefault(String givenValue, String expected,
+      Supplier<String> expensiveSupplier) {
+        String actual;
+        if (givenValue != null) {
+            actual = givenValue;
+        } else {
+            actual = expensiveSupplier.get();
+        }
+        assertDefaultConversion(givenValue, expected, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenTernaryWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = givenValue != null ? givenValue : defaultValue;
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsSupplierProvider.class)
+    void givenLazyTernaryWhenNotNullThenReturnsDefault(String givenValue, String expected,
+      Supplier<String> expensiveSupplier) {
+        String actual = givenValue != null ? givenValue : expensiveSupplier.get();
+        assertDefaultConversion(givenValue, expected, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenObjectsWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = requireNonNullElse(givenValue, defaultValue);
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsSupplierProvider.class)
+    void givenLazyObjectsWhenNotNullThenReturnsDefault(String givenValue, String expected,
+      Supplier<String> expensiveSupplier) {
+        String actual = requireNonNullElseGet(givenValue, expensiveSupplier);
+        assertDefaultConversion(givenValue, expected, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenOptionalWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = Optional.ofNullable(givenValue).orElse(defaultValue);
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsSupplierProvider.class)
+    void givenLazyOptionalWhenNotNullThenReturnsDefault(String givenValue, String expected,
+      Supplier<String> expensiveSupplier) {
+        String actual = Optional.ofNullable(givenValue).orElseGet(expensiveSupplier);
+        assertDefaultConversion(givenValue, expected, actual);
+    }
+
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenGuavaWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = MoreObjects.firstNonNull(givenValue, defaultValue);
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenGuavaOptionalWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = com.google.common.base.Optional.fromNullable(givenValue).or(defaultValue);
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsProvider.class)
+    void givenApacheWhenNotNullThenReturnsDefault(String givenValue, String defaultValue) {
+        String actual = ObjectUtils.firstNonNull(givenValue, defaultValue);
+        assertDefaultConversion(givenValue, defaultValue, actual);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(ObjectsSupplierProvider.class)
+    void givenLazyApacheWhenNotNullThenReturnsDefault(String givenValue, String expected,
+      Supplier<String> expensiveSupplier) {
+        String actual = ObjectUtils.getFirstNonNull(() -> givenValue, expensiveSupplier);
+        assertDefaultConversion(givenValue, expected, actual);
+    }
+
+    @Test
+    void givenAllNullsWithObjectsWhenNotNullThenThrowException() {
+        assertThatExceptionOfType(NullPointerException.class)
+          .isThrownBy(() -> requireNonNullElse(null, null));
+    }
+
+    private static void assertDefaultConversion(String given, String expected, String actual) {
+        if (given == null) {
+            assertThat(actual).isEqualTo(expected);
+        } else {
+            assertThat(actual).isEqualTo(given);
+        }
+    }
+
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/NullReturningPersonChainProvider.java

@@ -0,0 +1,26 @@
+package com.baeldung.nullconversion;
+
+import java.util.stream.Stream;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.ArgumentsProvider;
+
+public class NullReturningPersonChainProvider implements ArgumentsProvider {
+
+    @Override
+    public Stream<? extends Arguments> provideArguments(ExtensionContext context) {
+        Person person = new Person();
+        Address address = new Address();
+        ZipCode zipCode = new ZipCode("98-323");
+        address.setZipCode(zipCode);
+        person.setAddress(address);
+
+        return Stream.of(
+          Arguments.of(PersonMutatorUtil.cloneAndMutate(person, p -> p.getAddress().getZipCode().setCode(""))),
+          Arguments.of(PersonMutatorUtil.cloneAndMutate(person, p -> p.getAddress().setZipCode(null))),
+          Arguments.of(PersonMutatorUtil.cloneAndMutate(person, p -> p.setAddress(null)))
+        );
+
+    }
+
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/ObjectsProvider.java

@@ -0,0 +1,18 @@
+package com.baeldung.nullconversion;
+
+import java.util.stream.Stream;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.ArgumentsProvider;
+
+public class ObjectsProvider implements ArgumentsProvider {
+
+    @Override
+    public Stream<? extends Arguments> provideArguments(ExtensionContext context) {
+        return Stream.of(
+          Arguments.of(null, "default"),
+          Arguments.of("not null", "default")
+        );
+
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/ObjectsSupplierProvider.java

@@ -0,0 +1,20 @@
+package com.baeldung.nullconversion;
+
+import java.util.function.Supplier;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.ArgumentsProvider;
+
+public class ObjectsSupplierProvider implements ArgumentsProvider {
+
+    @Override
+    public Stream<? extends Arguments> provideArguments(ExtensionContext context) {
+        Supplier<String> supplier = () -> "default";
+        return Stream.of(
+          Arguments.of(null, "default", supplier),
+          Arguments.of("not null", "default", supplier)
+        );
+
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/OnePersonDeliveryServiceUnitTest.java

@@ -0,0 +1,31 @@
+package com.baeldung.nullconversion;
+
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+
+import com.baeldung.nullconversion.service.OnePersonExplicitDeliveryService;
+import com.baeldung.nullconversion.service.OnePersonGuavaOptionalDeliveryService;
+import com.baeldung.nullconversion.service.OnePersonOptionalDeliveryService;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ArgumentsSource;
+
+class OnePersonDeliveryServiceUnitTest {
+
+    @ParameterizedTest
+    @ArgumentsSource(PersonProvider.class)
+    void givenMockDeliverServiceWhenNullValuesThenExplicitServiceHandleThem(Person person, Delivery expected) {
+        DeliveryService deliveryService = new OnePersonExplicitDeliveryService(person);
+        Delivery actual = deliveryService.calculateDeliveryForPerson(1L);
+        assertThat(actual).isEqualTo(expected);
+    }
+
+    @ParameterizedTest
+    @ArgumentsSource(PersonProvider.class)
+    void givenMockDeliverServiceWhenNullValuesThenOptionalServiceHandleThem(Person person, Delivery expected) {
+        DeliveryService deliveryService = new OnePersonOptionalDeliveryService(person);
+        Delivery actual = deliveryService.calculateDeliveryForPerson(1L);
+        assertThat(actual).isEqualTo(expected);
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/PersonMutatorUtil.java

@@ -0,0 +1,12 @@
+package com.baeldung.nullconversion;
+
+import java.util.function.Consumer;
+
+public class PersonMutatorUtil {
+
+    public static Person cloneAndMutate(Person person, Consumer<Person> mutator) {
+        Person clone = person.clone();
+        mutator.accept(clone);
+        return clone;
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/PersonProvider.java

@@ -0,0 +1,34 @@
+package com.baeldung.nullconversion;
+
+import java.util.function.Consumer;
+import java.util.stream.Stream;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.ArgumentsProvider;
+
+public class PersonProvider implements ArgumentsProvider {
+
+    @Override
+    public Stream<? extends Arguments> provideArguments(ExtensionContext context) {
+        Person person = new Person();
+        Address address = new Address();
+        ZipCode zipCode = new ZipCode("98-323");
+        address.setZipCode(zipCode);
+        person.setAddress(address);
+
+        return Stream.of(
+          Arguments.of(person, Delivery.freeDelivery()),
+          Arguments.of(cloneAndMutate(person, p -> p.getAddress().getZipCode().setCode("")), Delivery.defaultDelivery()),
+          Arguments.of(cloneAndMutate(person, p -> p.getAddress().setZipCode(null)), Delivery.defaultDelivery()),
+          Arguments.of(cloneAndMutate(person, p -> p.setAddress(null)), Delivery.defaultDelivery()),
+          Arguments.of(null, Delivery.defaultDelivery())
+        );
+
+    }
+
+    private static Person cloneAndMutate(Person person, Consumer<Person> mutator) {
+        Person clone = person.clone();
+        mutator.accept(clone);
+        return clone;
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/service/MockOnePersonDeliveryServiceBase.java

@@ -0,0 +1,50 @@
+package com.baeldung.nullconversion.service;
+
+import com.baeldung.nullconversion.Address;
+import com.baeldung.nullconversion.Delivery;
+import com.baeldung.nullconversion.DeliveryService;
+import com.baeldung.nullconversion.Person;
+import com.baeldung.nullconversion.ZipCode;
+import java.util.Optional;
+
+public abstract class MockOnePersonDeliveryServiceBase implements DeliveryService {
+
+    private final Person person;
+
+    public MockOnePersonDeliveryServiceBase(Person person) {
+        this.person = person;
+    }
+
+    @Override
+    public Delivery calculateDeliveryForPerson(Long id) {
+        Person person = getPersonById(id);
+        if (person != null && person.getAddress() != null && person.getAddress().getZipCode() != null) {
+            ZipCode zipCode = person.getAddress().getZipCode();
+            String code = zipCode.getCode();
+            return calculateDeliveryForZipCode(code);
+        }
+        return Delivery.defaultDelivery();
+    }
+
+    public Delivery calculateDeliveryForPersonWithOptional(Long id) {
+        return Optional.ofNullable(getPersonById(id))
+          .map(Person::getAddress)
+          .map(Address::getZipCode)
+          .map(ZipCode::getCode)
+          .map(this::calculateDeliveryForZipCode)
+          .orElse(Delivery.defaultDelivery());
+    }
+
+    protected Person getPersonById(Long id) {
+        return person;
+    }
+
+    protected Delivery calculateDeliveryForZipCode(String zipCode) {
+        if (zipCode == null || zipCode.isEmpty()) {
+            return Delivery.defaultDelivery();
+        } else {
+            return Delivery.freeDelivery();
+        }
+    }
+
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/service/OnePersonExplicitDeliveryService.java

@@ -0,0 +1,24 @@
+package com.baeldung.nullconversion.service;
+
+import com.baeldung.nullconversion.Delivery;
+import com.baeldung.nullconversion.Person;
+import com.baeldung.nullconversion.ZipCode;
+
+public class OnePersonExplicitDeliveryService extends MockOnePersonDeliveryServiceBase {
+
+
+    public OnePersonExplicitDeliveryService(Person person) {
+        super(person);
+    }
+
+    @Override
+    public Delivery calculateDeliveryForPerson(Long id) {
+        Person person = getPersonById(id);
+        if (person != null && person.getAddress() != null && person.getAddress().getZipCode() != null) {
+            ZipCode zipCode = person.getAddress().getZipCode();
+            String code = zipCode.getCode();
+            return calculateDeliveryForZipCode(code);
+        }
+        return Delivery.defaultDelivery();
+    }
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/service/OnePersonGuavaOptionalDeliveryService.java

@@ -0,0 +1,26 @@
+package com.baeldung.nullconversion.service;
+
+import com.baeldung.nullconversion.Address;
+import com.baeldung.nullconversion.Delivery;
+import com.baeldung.nullconversion.Person;
+import com.baeldung.nullconversion.ZipCode;
+import com.google.common.base.Optional;
+
+public class OnePersonGuavaOptionalDeliveryService extends MockOnePersonDeliveryServiceBase {
+
+
+    public OnePersonGuavaOptionalDeliveryService(Person person) {
+        super(person);
+    }
+
+    @Override
+    public Delivery calculateDeliveryForPerson(Long id) {
+        return Optional.fromNullable(getPersonById(id))
+          .transform(Person::getAddress)
+          .transform(Address::getZipCode)
+          .transform(ZipCode::getCode)
+          .transform(this::calculateDeliveryForZipCode)
+          .or(Delivery.defaultDelivery());
+    }
+
+}

patterns-modules/design-patterns-behavioral-2/src/test/java/com/baeldung/nullconversion/service/OnePersonOptionalDeliveryService.java

@@ -0,0 +1,26 @@
+package com.baeldung.nullconversion.service;
+
+import com.baeldung.nullconversion.Address;
+import com.baeldung.nullconversion.Delivery;
+import com.baeldung.nullconversion.Person;
+import com.baeldung.nullconversion.ZipCode;
+import java.util.Optional;
+
+public class OnePersonOptionalDeliveryService extends MockOnePersonDeliveryServiceBase {
+
+
+    public OnePersonOptionalDeliveryService(Person person) {
+        super(person);
+    }
+
+    @Override
+    public Delivery calculateDeliveryForPerson(Long id) {
+        return Optional.ofNullable(getPersonById(id))
+          .map(Person::getAddress)
+          .map(Address::getZipCode)
+          .map(ZipCode::getCode)
+          .map(this::calculateDeliveryForZipCode)
+          .orElse(Delivery.defaultDelivery());
+    }
+
+}