BAEL-6142 Map clear methods in Java (#14255)

Co-authored-by: Mariam Momjyan <mmomjyan@vmware.com>

core-java-modules/core-java-collections-maps/src/main/java/com/baeldung/map/MapClear.java

@@ -0,0 +1,49 @@
+package com.baeldung.map;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class MapClear {
+    public static Map returnCopyAndClearMap() {
+        // Create a HashMap
+        Map<String, Integer> scores = new HashMap<>();
+        Map<String, Integer> scores_copy;
+
+        // Add some key-value pairs
+        scores.put("Alice", 90);
+        scores.put("Bob", 85);
+        scores.put("Charlie", 95);
+
+        scores_copy = scores;
+
+        System.out.println("Before clearing: " + scores);
+
+        // Clear the map
+        scores.clear();
+
+        System.out.println("After clearing: " + scores);
+        return scores_copy;
+    }
+
+    public static Map returnCopyAndRewriteMap() {
+        // Create a HashMap
+        Map<String, Integer> scores = new HashMap<>();
+        Map<String, Integer> scores_copy;
+
+        // Add some key-value pairs
+        scores.put("Alice", 90);
+        scores.put("Bob", 85);
+        scores.put("Charlie", 95);
+
+        scores_copy = scores;
+
+        System.out.println("Before clearing: " + scores);
+
+        // Create a new map
+        scores = new HashMap<>();
+
+        System.out.println("After clearing: " + scores);
+
+        return scores_copy;
+    }
+}

core-java-modules/core-java-collections-maps/src/test/java/com/baeldung/map/MapClearUnitTest.java

@@ -0,0 +1,20 @@
+package com.baeldung.map;
+
+import java.util.Map;
+
+import org.junit.Test;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class MapClearUnitTest {
+    @Test
+    public void givenMap_returnEntryAndClearContent() {
+        Map entry = MapClear.returnCopyAndClearMap();
+        assertTrue(entry.isEmpty());
+    }
+
+    @Test public void givenMap_returnEntryAndRewriteContent() {
+        Map entry = MapClear.returnCopyAndRewriteMap();
+        assertTrue(!entry.isEmpty());
+    }
+}