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BAEL-5419: List vs ArrayList in Java + tests (eugenp#11936)
* BAEL-5419: List vs ArrayList in Java + tests * BAEL-5419: Updated code +tests as per review comments * BAEL-5419: Fixed failing tests * BAEL-5419: Fixed JUnit test as per review comments
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‎core-java-modules/core-java-collections-list-3/src/main/java/com/baeldung/list/listvsarraylist/ArrayListDemo.java‎

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package com.baeldung.list.listvsarraylist;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.Locale;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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public class ArrayListDemo {
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private ArrayList<Passenger> passengers = new ArrayList<>(20);
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// private LinkedList<Passenger> passengers = new LinkedList<>(); // compile time error
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public ArrayList<Passenger> addPassenger(Passenger passenger) {
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passengers.add(passenger);
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return passengers;
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}
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public ArrayList<Passenger> removePassenger(Passenger passenger) {
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passengers.remove(passenger);
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return passengers;
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}
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public ArrayList<Passenger> getPassengersBySource(String source) {
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return new ArrayList<Passenger>(passengers.stream()
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.filter(it -> it.getSource().equals(source))
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.collect(Collectors.toList()));
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}
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public ArrayList<Passenger> getPassengersByDestination(String destination) {
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return new ArrayList<Passenger> (passengers.stream()
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.filter(it -> it.getDestination().equals(destination))
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.collect(Collectors.toList()));
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}
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public long getKidsCount(ArrayList<Passenger> passengerList) {
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return passengerList.stream()
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.filter(it -> (it.getAge() <= 10))
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.count();
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}
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public ArrayList<Passenger> getFinalPassengersList() {
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return new ArrayList<Passenger> (Collections.unmodifiableList(passengers));
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}
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public ArrayList<String> getServicedCountries() {
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return new ArrayList<String> (Stream.of(Locale.getISOCountries())
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.collect(Collectors.toList()));
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}
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}

‎core-java-modules/core-java-collections-list-3/src/main/java/com/baeldung/list/listvsarraylist/ListDemo.java‎

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package com.baeldung.list.listvsarraylist;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.LinkedList;
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import java.util.List;
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import java.util.Locale;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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public class ListDemo {
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private List<Passenger> passengers = new ArrayList<>(20);
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// private List<Passenger> passengers = new LinkedList<>(); // No compile time error
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public List<Passenger> addPassenger(Passenger passenger) {
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passengers.add(passenger);
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return passengers;
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}
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public List<Passenger> removePassenger(Passenger passenger) {
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passengers.remove(passenger);
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return passengers;
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}
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public List<Passenger> getPassengersBySource(String source) {
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return passengers.stream()
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.filter(it -> it.getSource().equals(source))
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.collect(Collectors.toList());
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}
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public List<Passenger> getPassengersByDestination(String destination) {
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return passengers.stream()
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.filter(it -> it.getDestination().equals(destination))
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.collect(Collectors.toList());
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}
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public long getKidsCount(List<Passenger> passengerList) {
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return passengerList.stream()
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.filter(it -> (it.getAge() <= 10))
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.count();
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}
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public List<Passenger> getFinalPassengersList() {
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return Collections.unmodifiableList(passengers);
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}
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public List<String> getServicedCountries() {
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return Stream.of(Locale.getISOCountries())
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.collect(Collectors.toList());
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}
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}

‎core-java-modules/core-java-collections-list-3/src/main/java/com/baeldung/list/listvsarraylist/Passenger.java‎

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package com.baeldung.list.listvsarraylist;
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public class Passenger {
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private String name;
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private int age;
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private String source;
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private String destination;
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public Passenger(String name, int age, String source, String destination) {
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this.name = name;
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this.age = age;
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this.source = source;
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this.destination = destination;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public int getAge() {
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return age;
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}
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public void setAge(int age) {
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this.age = age;
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}
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public String getSource() {
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return source;
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}
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public void setSource(String source) {
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this.source = source;
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}
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public String getDestination() {
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return destination;
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}
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public void setDestination(String destination) {
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this.destination = destination;
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}
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}

‎core-java-modules/core-java-collections-list-3/src/test/java/com/baeldung/list/listvsarraylist/ArrayListDemoUnitTest.java‎

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package com.baeldung.list.listvsarraylist;
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import static org.assertj.core.api.Assertions.assertThat;
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import static org.junit.Assert.assertNotNull;
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import java.util.ArrayList;
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import java.util.Locale;
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import org.junit.jupiter.api.BeforeEach;
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import org.junit.jupiter.api.Test;
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class ArrayListDemoUnitTest {
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ArrayListDemo application = new ArrayListDemo();
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Passenger passenger1;
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Passenger passenger2;
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Passenger passenger3;
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@BeforeEach
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protected void setUp() {
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passenger1 = new Passenger("Anna", 25, "London", "New York");
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passenger2 = new Passenger("Binny", 35, "New York", "London");
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passenger3 = new Passenger("Chandra", 8, "Paris", "New Delhi");
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application.addPassenger(passenger1);
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application.addPassenger(passenger2);
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application.addPassenger(passenger3);
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}
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@Test
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public void givenEmptyList_whenAddedPassenger_thenReturnCurrentPassengerList() {
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ArrayList<Passenger> list = application.addPassenger(new Passenger("David", 54, "Milan", "Paris"));
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assertNotNull(list);
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assertThat(list).hasSize(4);
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}
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@Test
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public void givenPassengerList_whenRemovedPassenger_thenReturnCurrentPassengerList() {
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ArrayList<Passenger> list = application.removePassenger(passenger3);
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assertNotNull(list);
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assertThat(list).hasSize(2);
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}
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@Test
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public void givenPassengerList_whenPassedWithSourceCity_thenReturnMatchingPassengerList() {
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ArrayList<Passenger> list = application.getPassengersBySource("Singapore");
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ArrayList<Passenger> list2 = application.getPassengersBySource("London");
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assertThat(list).isEmpty();
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assertThat(list2.get(0)).isEqualTo(passenger1);
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}
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@Test
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public void givenPassengerList_whenPassedWithDestinationCity_thenReturnMatchingPassengerList() {
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ArrayList<Passenger> list = application.getPassengersByDestination("Singapore");
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ArrayList<Passenger> list2 = application.getPassengersByDestination("London");
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assertThat(list).isEmpty();
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assertThat(list2.get(0)).isEqualTo(passenger2);
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}
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@Test
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public void givenPassengerList_whenFindKidsByAge_thenReturnKidsList() {
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ArrayList<Passenger> list = new ArrayList<>();
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list.add(passenger1);
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list.add(passenger2);
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list.add(passenger3);
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long count = application.getKidsCount(list);
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assertThat(count).isEqualTo(1);
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}
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@Test
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public void givenPassengerList_whenCalledWithCollectionsFunction_thenReturnsListType() {
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ArrayList<Passenger> list = application.getFinalPassengersList();
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assertNotNull(list);
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assertThat(list).hasSize(3);
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}
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@Test
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public void givenCurrentLocale_whenUsingStreams_thenReturnsListType() {
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ArrayList<String> servicedCountries = application.getServicedCountries();
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assertNotNull(servicedCountries);
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assertThat(servicedCountries).hasSize(Locale.getISOCountries().length);
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}
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}

‎core-java-modules/core-java-collections-list-3/src/test/java/com/baeldung/list/listvsarraylist/ListDemoUnitTest.java‎

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package com.baeldung.list.listvsarraylist;
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import static org.assertj.core.api.Assertions.assertThat;
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import static org.junit.Assert.assertNotNull;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.Locale;
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import org.junit.jupiter.api.BeforeEach;
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import org.junit.jupiter.api.Test;
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class ListDemoUnitTest {
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ListDemo application = new ListDemo();
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Passenger passenger1;
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Passenger passenger2;
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Passenger passenger3;
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@BeforeEach
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protected void setUp() {
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passenger1 = new Passenger("Anna", 25, "London", "New York");
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passenger2 = new Passenger("Binny", 35, "New York", "London");
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passenger3 = new Passenger("Chandra", 8, "Paris", "New Delhi");
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application.addPassenger(passenger1);
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application.addPassenger(passenger2);
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application.addPassenger(passenger3);
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}
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@Test
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public void givenEmptyList_whenAddedPassenger_thenReturnCurrentPassengerList() {
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List<Passenger> list = application.addPassenger(new Passenger("David", 54, "Milan", "Paris"));
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assertNotNull(list);
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assertThat(list).hasSize(4);
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}
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@Test
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public void givenPresentList_whenRemovedPassenger_thenReturnCurrentPassengerList() {
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List<Passenger> list = application.removePassenger(passenger3);
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assertNotNull(list);
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assertThat(list).hasSize(2);
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}
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@Test
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public void givenPresentList_whenPassedWithSourceCity_thenReturnMatchingPassengerList() {
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List<Passenger> list = application.getPassengersBySource("Singapore");
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List<Passenger> list2 = application.getPassengersBySource("London");
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assertThat(list).isEmpty();
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assertThat(list2.get(0)).isEqualTo(passenger1);
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}
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@Test
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public void givenPresentList_whenPassedWithDestinationCity_thenReturnMatchingPassengerList() {
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List<Passenger> list = application.getPassengersByDestination("Singapore");
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List<Passenger> list2 = application.getPassengersByDestination("London");
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assertThat(list).isEmpty();
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assertThat(list2.get(0)).isEqualTo(passenger2);
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}
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@Test
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public void givenPassengerList_whenFindKidsByAge_thenReturnKidsList() {
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List<Passenger> list = new ArrayList<>();
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list.add(passenger1);
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list.add(passenger2);
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list.add(passenger3);
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long count = application.getKidsCount(list);
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assertThat(count).isEqualTo(1);
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}
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@Test
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public void givenPresentList_whenCalledWithCollectionsFunction_thenReturnsListType() {
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List<Passenger> list = application.getFinalPassengersList();
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assertNotNull(list);
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assertThat(list).hasSize(3);
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}
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@Test
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public void givenCurrentLocale_whenUsingStreams_thenReturnsListType() {
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List<String> servicedCountries = application.getServicedCountries();
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assertNotNull(servicedCountries);
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assertThat(servicedCountries).hasSize(Locale.getISOCountries().length);
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}
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}

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