BAEL-3476: Add Java 9 example to Immutable ArrayList in Java (#8636)

core-java-modules/core-java-9/src/test/java/com/baeldung/java9/list/immutable/ImmutableArrayListUnitTest.java

@@ -0,0 +1,48 @@
+package com.baeldung.java9.list.immutable;
+
+import com.google.common.collect.ImmutableList;
+import org.apache.commons.collections4.ListUtils;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+public class ImmutableArrayListUnitTest {
+
+    @Test(expected = UnsupportedOperationException.class)
+    public final void givenUsingTheJdk_whenUnmodifiableListIsCreated_thenNotModifiable() {
+        final List<String> list = new ArrayList<>(Arrays.asList("one", "two", "three"));
+        final List<String> unmodifiableList = Collections.unmodifiableList(list);
+        unmodifiableList.add("four");
+    }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public final void givenUsingTheJava9_whenUnmodifiableListIsCreated_thenNotModifiable() {
+        final List<String> list = new ArrayList<>(Arrays.asList("one", "two", "three"));
+        final List<String> unmodifiableList = List.of(list.toArray(new String[]{}));
+        unmodifiableList.add("four");
+    }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public final void givenUsingGuava_whenUnmodifiableListIsCreated_thenNotModifiable() {
+        final List<String> list = new ArrayList<>(Arrays.asList("one", "two", "three"));
+        final List<String> unmodifiableList = ImmutableList.copyOf(list);
+        unmodifiableList.add("four");
+    }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public final void givenUsingGuavaBuilder_whenUnmodifiableListIsCreated_thenNoLongerModifiable() {
+        final List<String> list = new ArrayList<>(Arrays.asList("one", "two", "three"));
+        final ImmutableList<String> unmodifiableList = ImmutableList.<String>builder().addAll(list).build();
+        unmodifiableList.add("four");
+    }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public final void givenUsingCommonsCollections_whenUnmodifiableListIsCreated_thenNotModifiable() {
+        final List<String> list = new ArrayList<>(Arrays.asList("one", "two", "three"));
+        final List<String> unmodifiableList = ListUtils.unmodifiableList(list);
+        unmodifiableList.add("four");
+    }
+}