[BAEL-2170] Differences between ArrayList clear and removeAll

core-java-collections/src/test/java/com/baeldung/list/arraylist/ClearVsRemoveAllTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.list.arraylist;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Unit tests demonstrating differences between ArrayList#clear() and ArrayList#removeAll()
+ */
+class ClearVsRemoveAllTest {
+
+    /*
+     * Tests
+     */
+    @Test
+    void givenArrayListWithElements_whenClear_thenListBecomesEmpty() {
+        ArrayList<Integer> list = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));
+
+        list.clear();
+
+        assertTrue(list.isEmpty());
+    }
+
+    @Test
+    void givenTwoArrayListsWithCommonElements_whenRemoveAll_thenFirstListMissElementsFromSecondList() {
+        ArrayList<Integer> firstList = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));
+        ArrayList<Integer> secondList = new ArrayList<>(Arrays.asList(3, 4, 5, 6, 7));
+
+        firstList.removeAll(secondList);
+
+        assertEquals(Arrays.asList(1, 2), firstList);
+    }
+
+}