JAVA-5683: Difference Between List.of and Arrays.asList (#12564)

Co-authored-by: Harpal Singh <harpal.singh@kaleyra.com>

core-java-modules/core-java-collections-list-4/pom.xml

@@ -64,6 +64,23 @@
         <colt.version>1.2.0</colt.version>
         <apache-commons.version>3.0</apache-commons.version>
         <assertj.version>3.22.0</assertj.version>
+        <maven.compiler.source.version>17</maven.compiler.source.version>
+        <maven.compiler.target.version>17</maven.compiler.target.version>
+       
     </properties>
     
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source.version}</source>
+                    <target>${maven.compiler.target.version}</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
 </project>

core-java-modules/core-java-collections-list-4/src/test/java/com/baeldung/list/creation/ArraysAsListUnitTest.java

@@ -0,0 +1,56 @@
+package com.baeldung.list.creation;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class ArraysAsListUnitTest {
+
+    @Test
+    void givenAnArrayOfIntegersWhenCreatingAListUsingArraysAsListThenItWillHaveTheSameElementsInTheSameOrder() {
+        Integer[] array = new Integer[]{1, 2, 3, 4};
+        List<Integer> list = Arrays.asList(array);
+        assertThat(list).containsExactly(1, 2, 3, 4);
+    }
+
+    @Test
+    void givenAnListOfIntegersCreatedUsingArraysAsListWhenChangingTheOriginalArrayTheReturnListWillAlsoChange() {
+        Integer[] array = new Integer[]{1, 2, 3};
+        List<Integer> list = Arrays.asList(array);
+        array[0] = 1000;
+        assertThat(list.get(0)).isEqualTo(1000);
+    }
+
+    @Test
+    void givenAnListOfIntegersCreatedUsingArraysAsListWhenChangingTheReturnedListTheOriginalArrayWillAlsoChange() {
+        Integer[] array = new Integer[]{1, 2, 3};
+        List<Integer> list = Arrays.asList(array);
+        list.set(0, 1000);
+        assertThat(array[0]).isEqualTo(1000);
+    }
+
+    @Test
+    void givenAnArrayOfIntegersCreatedUsingArraysAsListWhenModifyingAnExistingElementThenModifyIt() {
+        List<Integer> list = Arrays.asList(1, 2, 3, 4);
+        list.set(1, 1000);
+        assertThat(list.get(1)).isEqualTo(1000);
+    }
+
+    @Test
+    void givenAnArrayCreatedWithArraysAsListWhenAddingANewElementThenUnsupportedOperationExceptionIsThrown() {
+        List<Integer> list = Arrays.asList(1, 2, 3, 4, 5);
+        assertThrows(UnsupportedOperationException.class, () -> list.add(6));
+    }
+
+    @Test
+    void givenAnArrayCreatedWithArraysAsListWhenRemovingAnExistingElementThenUnsupportedOperationExceptionIsThrown() {
+        List<Integer> list = Arrays.asList(1, 2, 3, 4, 5);
+        assertThrows(UnsupportedOperationException.class, () -> list.remove(1));
+    }
+
+
+}

core-java-modules/core-java-collections-list-4/src/test/java/com/baeldung/list/creation/ListOfUnitTest.java

@@ -0,0 +1,51 @@
+package com.baeldung.list.creation;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class ListOfUnitTest {
+
+    @Test
+    void givenAnArrayOfStringWhenCreatingAListUsingItsValuesThenItWillHaveTheSameElementsInTheSameOrder() {
+        String[] array = new String[]{"one", "two", "three"};
+        List<String> list = List.of(array);
+        assertThat(list).containsExactly("one", "two", "three");
+    }
+
+    @Test
+    void givenAnListOfStringCreatedUsingListOfWhenChangingTheOriginalArrayTheReturnListWontChange() {
+        String[] array = new String[]{"one", "two", "three"};
+        List<String> list = List.of(array);
+        array[0] = "thousand";
+        assertThat(list.get(0)).isEqualTo("one");
+    }
+
+    @Test
+    void givenAnArrayCreatedWithListOfWhenAddingANewElementThenUnsupportedOperationExceptionIsThrown() {
+        List<String> list = List.of("one", "two", "three");
+        assertThrows(UnsupportedOperationException.class, () -> list.add("four"));
+    }
+
+    @Test
+    void givenAnArrayCreatedWithListOfWhenRemovingAnExistingElementThenUnsupportedOperationExceptionIsThrown() {
+        List<String> list = List.of("one", "two", "three");
+        assertThrows(UnsupportedOperationException.class, () -> list.remove("two"));
+    }
+
+    @Test
+    void givenAnArrayCreatedWithListOfWhenModifyingAnExistingElementThenUnsupportedOperationExceptionIsThrown() {
+        List<String> list = List.of("one", "two", "three");
+        assertThrows(UnsupportedOperationException.class, () -> list.set(1, "four"));
+    }
+
+    @Test
+    void givenAnArrayContainingNullElementWhenUsingItToCreateListThenNullPointerExceptionIsThrown() {
+        assertThrows(NullPointerException.class, () -> List.of("one", null, "two"));
+    }
+
+
+}

core-java-modules/pom.xml

@@ -37,7 +37,6 @@
         <module>core-java-collections-list</module>
         <module>core-java-collections-list-2</module>
         <module>core-java-collections-list-3</module>
-        <module>core-java-collections-list-4</module>
         <module>core-java-collections-maps</module>
         <module>core-java-collections-maps-2</module>
         <module>core-java-collections-maps-3</module>

pom.xml

@@ -1161,6 +1161,7 @@
                  <!-- <module>core-java-modules/core-java-16</module> --> <!-- uses preview features, to be decided how to handle -->
                  <!-- <module>core-java-modules/core-java-17</module> --> <!-- uses preview features, to be decided how to handle -->
                  <module>core-java-modules/core-java-collections-set</module>
+                 <module>core-java-modules/core-java-collections-list-4</module>
                  <module>core-java-modules/core-java-collections-maps-4</module>
                  <module>core-java-modules/core-java-date-operations-1</module>
                  <module>core-java-modules/core-java-datetime-conversion</module>
@@ -1234,6 +1235,7 @@
                 <!-- <module>core-java-modules/core-java-16</module> --> <!-- uses preview features, to be decided how to handle -->
                 <!-- <module>core-java-modules/core-java-17</module> --> <!-- uses preview features, to be decided how to handle -->
                 <module>core-java-modules/core-java-collections-set</module>
+                <module>core-java-modules/core-java-collections-list-4</module>
                 <module>core-java-modules/core-java-collections-maps-4</module>
                 <module>core-java-modules/core-java-date-operations-1</module>
                 <module>core-java-modules/core-java-datetime-conversion</module>