Inheritance and Composition (Is-a vs Has-a relationship) in Java - BAEL-1598

core-java/src/main/java/com/baeldung/inheritancecomposition/application/Application.java

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+package com.baeldung.inheritancecomposition.application;
+
+import com.baeldung.inheritancecomposition.model.Actress;
+import com.baeldung.inheritancecomposition.model.Computer;
+import com.baeldung.inheritancecomposition.model.StandardMemory;
+import com.baeldung.inheritancecomposition.model.Person;
+import com.baeldung.inheritancecomposition.model.StandardProcessor;
+import com.baeldung.inheritancecomposition.model.StandardSoundCard;
+import com.baeldung.inheritancecomposition.model.Waitress;
+
+public class Application {
+
+    public static void main(String[] args) {
+
+        Person person = new Person("John", "john@domain.com", 35);
+        Waitress waitress = new Waitress("Mary", "mary@domain.com", 22);
+        System.out.println(waitress.serveStarter("mixed salad"));
+        System.out.println(waitress.serveMainCourse("steak"));
+        System.out.println(waitress.serveDessert("cup of cofee"));
+        Actress actress = new Actress("Susan", "susan@domain.com", 30);
+        System.out.println(actress.readScript("Psycho"));
+        System.out.println(actress.performRole());
+        Computer computer = new Computer(new StandardProcessor("Intel I3"), new StandardMemory("Kingston", "1TB"));
+        computer.setSoundCard(new StandardSoundCard("Generic Sound Card"));
+        System.out.println(computer);
+    }
+}

core-java/src/main/java/com/baeldung/inheritancecomposition/model/Actress.java

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+package com.baeldung.inheritancecomposition.model;
+
+public class Actress extends Person {
+
+    public Actress(String name, String email, int age) {
+        super(name, email, age);
+    }
+
+    public String readScript(String movie) {
+        return "Reading the script of " + movie;
+    }
+
+    public String performRole() {
+        return "Performing a role";
+    }
+}

core-java/src/main/java/com/baeldung/inheritancecomposition/model/Computer.java

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+package com.baeldung.inheritancecomposition.model;
+
+import java.util.Optional;
+
+public class Computer {
+
+    private Processor processor;
+    private Memory memory;
+    private SoundCard soundCard;
+
+    public Computer(Processor processor, Memory memory) {
+        this.processor = processor;
+        this.memory = memory;
+    }
+
+    public void setSoundCard(SoundCard soundCard) {
+        this.soundCard = soundCard;
+    }
+
+    public Processor getProcessor() {
+        return processor;
+    }
+
+    public Memory getMemory() {
+        return memory;
+    }
+
+    public Optional<SoundCard> getSoundCard() {
+        return Optional.ofNullable(soundCard);
+    }
+
+    @Override
+    public String toString() {
+        return "Computer{" + "processor=" + processor + ", memory=" + memory + ", soundcard=" + soundCard +"}";
+    }
+}

core-java/src/main/java/com/baeldung/inheritancecomposition/model/Memory.java

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+package com.baeldung.inheritancecomposition.model;
+
+public interface Memory {
+
+    String getBrand();
+
+    String getSize();   
+}

core-java/src/main/java/com/baeldung/inheritancecomposition/model/Person.java

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+package com.baeldung.inheritancecomposition.model;
+
+public class Person {
+
+    private final String name;
+    private final String email;
+    private final int age;
+
+    public Person(String name, String email, int age) {
+        this.name = name;
+        this.email = email;
+        this.age = age;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    @Override
+    public String toString() {
+        return "Person{" + "name=" + name + ", email=" + email + ", age=" + age + "}";
+    }
+}

core-java/src/main/java/com/baeldung/inheritancecomposition/model/Processor.java

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+package com.baeldung.inheritancecomposition.model;
+
+public interface Processor {
+
+    String getModel();
+}

core-java/src/main/java/com/baeldung/inheritancecomposition/model/SoundCard.java

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+package com.baeldung.inheritancecomposition.model;
+
+public interface SoundCard {
+
+    String getBrand();
+}

core-java/src/main/java/com/baeldung/inheritancecomposition/model/StandardMemory.java

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+package com.baeldung.inheritancecomposition.model;
+
+public class StandardMemory implements Memory {
+
+    private String brand;
+    private String size;
+
+    public StandardMemory(String brand, String size) {
+        this.brand = brand;
+        this.size = size;
+    }
+
+    public String getBrand() {
+        return brand;
+    }
+
+    public String getSize() {
+        return size;
+    }
+
+    @Override
+    public String toString() {
+        return "Memory{" + "brand=" + brand + ", size=" + size + "}";
+    }
+}

core-java/src/main/java/com/baeldung/inheritancecomposition/model/StandardProcessor.java

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+package com.baeldung.inheritancecomposition.model;
+
+public class StandardProcessor implements Processor {
+
+    private String model;
+
+    public StandardProcessor(String model) {
+        this.model = model;
+    }
+
+    @Override
+    public String getModel() {
+        return model;
+    }
+
+    @Override
+    public String toString() {
+        return "Processor{" + "model=" + model + "}";
+    }
+}

core-java/src/main/java/com/baeldung/inheritancecomposition/model/StandardSoundCard.java

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+package com.baeldung.inheritancecomposition.model;
+
+public class StandardSoundCard implements SoundCard {
+
+    private String brand;
+
+    public StandardSoundCard(String brand) {
+        this.brand = brand;
+    }
+
+    @Override
+    public String getBrand() {
+        return brand;
+    }
+
+    @Override
+    public String toString() {
+        return "SoundCard{" + "brand=" + brand + "}";
+    }  
+}

core-java/src/main/java/com/baeldung/inheritancecomposition/model/Waitress.java

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+package com.baeldung.inheritancecomposition.model;
+
+public class Waitress extends Person {
+
+    public Waitress(String name, String email, int age) {
+        super(name, email, age);
+    }
+
+    public String serveStarter(String starter) {
+        return "Serving a " + starter;
+    }
+
+    public String serveMainCourse(String mainCourse) {
+        return "Serving a " + mainCourse;
+    }
+
+    public String serveDessert(String dessert) {
+        return "Serving a " + dessert;
+    }
+}

core-java/src/test/java/com/baeldung/inheritancecomposition/test/ActressUnitTest.java

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+package com.baeldung.inheritancecomposition.test;
+
+import com.baeldung.inheritancecomposition.model.Actress;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import static org.assertj.core.api.Assertions.*;
+
+public class ActressUnitTest {
+
+    private static Actress actress;
+
+    @BeforeClass
+    public static void setUpActressInstance() {
+        actress = new Actress("Susan", "susan@domain.com", 30);
+    }
+
+    @Test
+    public void givenActressInstance_whenCalledgetName_thenEqual() {
+        assertThat(actress.getName()).isEqualTo("Susan");
+    }
+
+    @Test
+    public void givenActressInstance_whenCalledgetEmail_thenEqual() {
+        assertThat(actress.getEmail()).isEqualTo("susan@domain.com");
+    }
+
+    @Test
+    public void givenActressInstance_whenCalledgetAge_thenEqual() {
+        assertThat(actress.getAge()).isEqualTo(30);
+    }
+
+    @Test
+    public void givenActressInstance_whenCalledreadScript_thenEqual() {
+        assertThat(actress.readScript("Psycho")).isEqualTo("Reading the script of Psycho");
+    }
+
+    @Test
+    public void givenActressInstance_whenCalledperfomRole_thenEqual() {
+        assertThat(actress.performRole()).isEqualTo("Performing a role");
+    }
+}

core-java/src/test/java/com/baeldung/inheritancecomposition/test/CompositionUnitTest.java

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+package com.baeldung.inheritancecomposition.test;
+
+import com.baeldung.inheritancecomposition.model.Computer;
+import com.baeldung.inheritancecomposition.model.Memory;
+import com.baeldung.inheritancecomposition.model.Processor;
+import com.baeldung.inheritancecomposition.model.StandardMemory;
+import com.baeldung.inheritancecomposition.model.StandardProcessor;
+import com.baeldung.inheritancecomposition.model.StandardSoundCard;
+import java.util.Optional;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.Test;
+
+public class CompositionUnitTest {
+
+
+    @Test
+    public void givenComputerInstance_whenExtractedEachField_thenThreeAssertions() {
+        Computer computer = new Computer(new StandardProcessor("Intel I3"), new StandardMemory("Kingston", "1TB"));
+        computer.setSoundCard(new StandardSoundCard("Generic Sound Card"));
+        assertThat(computer.getProcessor()).isInstanceOf(Processor.class);
+        assertThat(computer.getMemory()).isInstanceOf(Memory.class);
+        assertThat(computer.getSoundCard()).isInstanceOf(Optional.class);
+    }
+}

core-java/src/test/java/com/baeldung/inheritancecomposition/test/InheritanceUnitTest.java

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+package com.baeldung.inheritancecomposition.test;
+
+import com.baeldung.inheritancecomposition.model.Actress;
+import com.baeldung.inheritancecomposition.model.Person;
+import com.baeldung.inheritancecomposition.model.Waitress;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.Test;
+
+public class InheritanceUnitTest {
+
+    @Test
+    public void givenWaitressInstance_whenCheckedType_thenIsInstanceOfPerson() {
+        assertThat(new Waitress("Mary", "mary@domain.com", 22)).isInstanceOf(Person.class);
+    }
+
+    @Test
+    public void givenActressInstance_whenCheckedType_thenIsInstanceOfPerson() {
+        assertThat(new Actress("Susan", "susan@domain.com", 30)).isInstanceOf(Person.class);
+    }
+}

core-java/src/test/java/com/baeldung/inheritancecomposition/test/PersonUnitTest.java

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+package com.baeldung.inheritancecomposition.test;
+
+import com.baeldung.inheritancecomposition.model.Person;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import static org.assertj.core.api.Assertions.*;
+
+public class PersonUnitTest {
+
+    private static Person person;
+
+    @BeforeClass
+    public static void setPersonInstance() {
+        person = new Person("John", "john@domain.com", 35);
+    }
+
+    @Test
+    public void givenPersonInstance_whenCalledgetName_thenEqual() {
+        assertThat(person.getName()).isEqualTo("John");
+    }
+
+    @Test
+    public void givenPersonInstance_whenCalledgetEmail_thenEqual() {
+        assertThat(person.getEmail()).isEqualTo("john@domain.com");
+    }
+
+    @Test
+    public void givenPersonInstance_whenCalledgetAge_thenEqual() {
+        assertThat(person.getAge()).isEqualTo(35);
+    }
+}

core-java/src/test/java/com/baeldung/inheritancecomposition/test/WaitressUnitTest.java

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+package com.baeldung.inheritancecomposition.test;
+
+import com.baeldung.inheritancecomposition.model.Waitress;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import static org.assertj.core.api.Assertions.*;
+
+public class WaitressUnitTest {
+
+    private static Waitress waitress;
+
+    @BeforeClass
+    public static void setUpWaitressInstance() {
+        waitress = new Waitress("Mary", "mary@domain.com", 22);
+    }
+
+    @Test
+    public void givenWaitressInstance_whenCalledgetName_thenOneAssertion() {
+        assertThat(waitress.getName()).isEqualTo("Mary");
+    }
+
+    @Test
+    public void givenWaitressInstance_whenCalledgetEmail_thenOneAssertion() {
+        assertThat(waitress.getEmail()).isEqualTo("mary@domain.com");
+    }
+
+    @Test
+    public void givenWaitressInstance_whenCalledgetAge_thenOneAssertion() {
+        assertThat(waitress.getAge()).isEqualTo(22);
+    }
+
+    @Test
+    public void givenWaitressInstance_whenCalledserveStarter_thenOneAssertion() {
+        assertThat(waitress.serveStarter("mixed salad")).isEqualTo("Serving a mixed salad");
+    }
+
+    @Test
+    public void givenWaitressInstance_whenCalledserveMainCourse_thenOneAssertion() {
+        assertThat(waitress.serveMainCourse("steak")).isEqualTo("Serving a steak");
+    }
+
+    @Test
+    public void givenWaitressInstance_whenCalledserveDessert_thenOneAssertion() {
+        assertThat(waitress.serveDessert("cup of coffee")).isEqualTo("Serving a cup of coffee");
+    }
+}