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bhaskar16Bhaskar-Dastidar-E3295
bhaskar16
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Bhaskar-Dastidar-E3295
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[JAVA-5730] convert list of objects to list of strings (#13166)
* [JAVA-5730] convert list of objects to list of strings * [JAVA-5730] added new unit tests with null and non-null lists. modified pom.xml with java version to 16 * [JAVA-5730] simplified User class and formatted the codebase * [JAVA-5730] added module in jdk-9 and above profile * [JAVA-5730] removed arraylist module from other profiles of core-java pom * [JAVA-5730] java util opened for reflection surefire plugin Co-authored-by: Bhaskar <bhaskar.dastidar@freshworks.com>
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‎core-java-modules/core-java-collections-array-list/pom.xml‎

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<modelVersion>4.0.0</modelVersion>
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<artifactId>core-java-collections-array-list</artifactId>
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<version>0.1.0-SNAPSHOT</version>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<configuration>
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<source>${maven-compiler-plugin.source}</source>
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<target>${maven-compiler-plugin.target}</target>
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</configuration>
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</plugin>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-surefire-plugin</artifactId>
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<version>${surefire.plugin.version}</version>
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<configuration>
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<argLine>
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--add-opens java.base/java.util=ALL-UNNAMED
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</argLine>
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</configuration>
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</plugin>
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</plugins>
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</build>
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<properties>
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<maven-compiler-plugin.source>16</maven-compiler-plugin.source>
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<maven-compiler-plugin.target>16</maven-compiler-plugin.target>
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<surefire.plugin.version>3.0.0-M3</surefire.plugin.version>
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</properties>
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<name>core-java-collections-array-list</name>
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<packaging>jar</packaging>
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<artifactId>commons-collections4</artifactId>
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<version>${commons-collections4.version}</version>
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</dependency>
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<dependency>
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<groupId>com.google.guava</groupId>
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<artifactId>guava</artifactId>
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<version>31.1-jre</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

‎core-java-modules/core-java-collections-array-list/src/main/java/com/baeldung/listofobjectstolistofstring/Node.java‎

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package com.baeldung.listofobjectstolistofstring;
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public class Node {
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private final int x;
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private final int y;
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public Node(int x, int y) {
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this.x = x;
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this.y = y;
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}
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@Override
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public String toString() {
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return "Node (" + "x=" + x + ", y=" + y + ')';
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}
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}

‎core-java-modules/core-java-collections-array-list/src/main/java/com/baeldung/listofobjectstolistofstring/User.java‎

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package com.baeldung.listofobjectstolistofstring;
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public class User {
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private final String fullName;
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public User(String fullName) {
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this.fullName = fullName;
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}
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@Override
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public String toString() {
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return "User (" + "full name='" + fullName + ')';
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}
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}

‎core-java-modules/core-java-collections-array-list/src/test/java/com/baeldung/listofobjectstolistofstring/ConvertObjectListToStringListUnitTest.java‎

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package com.baeldung.listofobjectstolistofstring;
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import com.google.common.collect.Lists;
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import org.junit.Assert;
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import org.junit.Test;
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import java.util.ArrayList;
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import java.util.List;
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import java.util.Objects;
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import java.util.stream.Collectors;
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public class ConvertObjectListToStringListUnitTest {
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@Test
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public void givenObjectList_whenForEachUsedToConvert_thenReturnSuccess() {
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List<String> outputList = new ArrayList<>(objectListWithNull().size());
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for (Object obj : objectListWithNull()) {
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outputList.add(Objects.toString(obj, null));
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}
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Assert.assertEquals(expectedStringListWithNull(), outputList);
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}
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@Test
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public void givenObjectList_whenUsingStreamsToConvert_thenReturnSuccess() {
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List<String> outputList;
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outputList = objectListWithNull().stream()
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.map((obj) -> Objects.toString(obj, null))
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.collect(Collectors.toList());
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Assert.assertEquals(expectedStringListWithNull(), outputList);
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}
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@Test
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public void givenObjectList_whenUsingStreamsUnmodifiableListToConvert_thenReturnSuccess() {
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List<String> outputList;
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outputList = objectListWithNull().stream()
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.filter(Objects::nonNull)
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.map((obj) -> Objects.toString(obj, null))
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.collect(Collectors.toUnmodifiableList());
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Assert.assertEquals(expectedStringListWithoutNull(), outputList);
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}
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@Test
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public void givenObjectList_whenUsingGuavaTransform_thenReturnSuccess() {
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List<String> outputList;
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outputList = Lists.transform(objectListWithNull(), obj -> Objects.toString(obj, null));
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Assert.assertEquals(expectedStringListWithNull(), outputList);
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}
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@Test
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public void givenObjectListWithNoNull_whenUsingToList_thenReturnSuccess() {
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List<String> outputList;
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outputList = objectListWithoutNull().stream()
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.map((obj) -> Objects.toString(obj, null))
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.toList();
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Assert.assertEquals(expectedStringListWithoutNull(), outputList);
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}
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private List<String> expectedStringListWithNull() {
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List<String> listOfStrings = new ArrayList<>();
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listOfStrings.add("1");
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listOfStrings.add("true");
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listOfStrings.add("hello");
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listOfStrings.add(Double.toString(273773.98));
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listOfStrings.add(null);
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listOfStrings.add(new Node(2, 4).toString());
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listOfStrings.add(new User("John Doe").toString());
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return listOfStrings;
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}
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private List<Object> objectListWithNull() {
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List<Object> listOfStrings = new ArrayList<>();
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listOfStrings.add(1);
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listOfStrings.add(true);
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listOfStrings.add("hello");
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listOfStrings.add(Double.valueOf(273773.98));
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listOfStrings.add(null);
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listOfStrings.add(new Node(2, 4));
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listOfStrings.add(new User("John Doe"));
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return listOfStrings;
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}
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private List<String> expectedStringListWithoutNull() {
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return List.of("1", "true", "hello", Double.toString(273773.98), new Node(2, 4).toString(), new User("John Doe").toString());
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}
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private List<Object> objectListWithoutNull() {
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return List.of(1, true, "hello", Double.valueOf(273773.98), new Node(2, 4), new User("John Doe"));
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}
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}

‎core-java-modules/pom.xml‎

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<module>core-java-collections-2</module>
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<module>core-java-collections-3</module>
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<module>core-java-collections-4</module>
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<module>core-java-collections-array-list</module>
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<module>core-java-collections-conversions</module>
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<module>core-java-collections-conversions-2</module>
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<module>core-java-collections-set-2</module>

‎pom.xml‎

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<!-- <module>core-java-modules/core-java-19</module> --> <!-- uses preview features, to be decided how to handle -->
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<module>core-java-modules/core-java-collections-set</module>
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<module>core-java-modules/core-java-collections-list-4</module>
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<module>core-java-modules/core-java-collections-array-list</module>
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<module>core-java-modules/core-java-collections-maps-4</module>
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<module>core-java-modules/core-java-collections-maps-5</module>
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<module>core-java-modules/core-java-concurrency-simple</module>

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