Update README.md

immutables/README.md

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+## Immutables
+
+This module contains articles about the Immutables library.
+
+### Relevant Articles:
+- [Introduction to Immutables](https://www.baeldung.com/immutables)

immutables/pom.xml

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+<?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>immutables</artifactId>
+    <name>immutables</name>
+    
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.immutables</groupId>
+            <artifactId>value</artifactId>
+            <version>${immutables.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.mutabilitydetector</groupId>
+            <artifactId>MutabilityDetector</artifactId>
+            <version>${mutabilitydetector.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <immutables.version>2.5.6</immutables.version>
+        <assertj.version>3.6.1</assertj.version>
+        <mutabilitydetector.version>0.9.6</mutabilitydetector.version>
+    </properties>
+
+</project>

immutables/src/main/java/com/baeldung/immutable/Address.java

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+package com.baeldung.immutable;
+
+import org.immutables.value.Value;
+
+@Value.Immutable
+public interface Address {
+    String getStreetName();
+    Integer getNumber();
+}

immutables/src/main/java/com/baeldung/immutable/Person.java

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+package com.baeldung.immutable;
+
+import org.immutables.value.Value;
+
+@Value.Immutable
+public abstract class Person {
+    abstract String getName();
+    abstract Integer getAge();
+}

immutables/src/main/java/com/baeldung/immutable/auxiliary/Person.java

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+package com.baeldung.immutable.auxiliary;
+
+
+import org.immutables.value.Value;
+
+@Value.Immutable
+public abstract class Person {
+    abstract String getName();
+    abstract Integer getAge();
+
+    @Value.Auxiliary
+    abstract String getAuxiliaryField();
+}

immutables/src/main/java/com/baeldung/immutable/default_/Person.java

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+package com.baeldung.immutable.default_;
+
+import org.immutables.value.Value;
+
+@Value.Immutable(prehash = true)
+public abstract class Person {
+
+    abstract String getName();
+
+    @Value.Default
+    Integer getAge() {
+        return 42;
+    }
+}

immutables/src/main/java/com/baeldung/immutable/parameter/Person.java

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+package com.baeldung.immutable.parameter;
+
+
+import org.immutables.value.Value;
+
+@Value.Immutable
+public abstract class Person {
+
+    @Value.Parameter
+    abstract String getName();
+
+    @Value.Parameter
+    abstract Integer getAge();
+}

immutables/src/main/java/com/baeldung/immutable/prehash/Person.java

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+package com.baeldung.immutable.prehash;
+
+import org.immutables.value.Value;
+
+@Value.Immutable(prehash = true)
+public abstract class Person {
+    abstract String getName();
+    abstract Integer getAge();
+}

immutables/src/main/resources/logback.xml

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

immutables/src/test/java/com/baeldung/immutable/ImmutablePersonUnitTest.java

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+package com.baeldung.immutable;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mutabilitydetector.unittesting.MutabilityAssert.assertImmutable;
+
+public class ImmutablePersonUnitTest {
+
+    @Test
+    public void whenModifying_shouldCreateNewInstance() throws Exception {
+        final ImmutablePerson john = ImmutablePerson.builder()
+          .age(42)
+          .name("John")
+          .build();
+
+        final ImmutablePerson john43 = john.withAge(43);
+
+        assertThat(john)
+          .isNotSameAs(john43);
+
+        assertThat(john.getAge())
+          .isEqualTo(42);
+
+        assertImmutable(ImmutablePerson.class);
+    }
+}

immutables/src/test/java/com/baeldung/immutable/auxiliary/ImmutablePersonAuxiliaryUnitTest.java

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+package com.baeldung.immutable.auxiliary;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ImmutablePersonAuxiliaryUnitTest {
+
+    @Test
+    public void whenComparing_shouldIgnore() throws Exception {
+        final ImmutablePerson john1 = ImmutablePerson.builder()
+          .name("John")
+          .age(42)
+          .auxiliaryField("Value1")
+          .build();
+
+        final ImmutablePerson john2 = ImmutablePerson.builder()
+          .name("John")
+          .age(42)
+          .auxiliaryField("Value2")
+          .build();
+
+
+        assertThat(john1.equals(john2))
+          .isTrue();
+
+        assertThat(john1.toString())
+          .isEqualTo(john2.toString());
+
+        assertThat(john1.hashCode())
+          .isEqualTo(john2.hashCode());
+    }
+}

immutables/src/test/java/com/baeldung/immutable/default_/ImmutablePersonDefaultUnitTest.java

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+package com.baeldung.immutable.default_;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ImmutablePersonDefaultUnitTest {
+
+    @Test
+    public void whenInstantiating_shouldUseDefaultValue() throws Exception {
+
+        final ImmutablePerson john = ImmutablePerson.builder().name("John").build();
+
+        assertThat(john.getAge()).isEqualTo(42);
+
+    }
+}