diff --git a/core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/concurrenthashmap/NullAllowInMapTest.java b/core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/concurrenthashmap/NullAllowInMapTest.java
new file mode 100644
index 0000000000..23c76e59e8
--- /dev/null
+++ b/core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/concurrenthashmap/NullAllowInMapTest.java
@@ -0,0 +1,27 @@
+package com.baeldung.map.concurrenthashmap;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class NullAllowInMapTest {
+    
+    @Test
+    public void allowOnlyNull_In_SynchronizedMap() {
+        Map<String, Integer> map = Collections
+                .synchronizedMap(new HashMap<String, Integer>());
+        map.put(null, 1);
+        Assert.assertTrue(map.get(null).equals(1));
+    }
+    
+    @Test(expected = NullPointerException.class)
+    public void allowOnlyNull_In_ConcurrentHasMap() {
+        Map<String, Integer> map = new ConcurrentHashMap<>();
+        map.put(null, 1);
+    }
+    
+}
diff --git a/core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/concurrenthashmap/ConcurrentHashMapVsSynchronizedMapPerformanceTest.java b/core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/concurrenthashmap/PerformanceTest.java
similarity index 99%
rename from core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/concurrenthashmap/ConcurrentHashMapVsSynchronizedMapPerformanceTest.java
rename to core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/concurrenthashmap/PerformanceTest.java
index 573087d5a5..5321d33b36 100644
--- a/core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/concurrenthashmap/ConcurrentHashMapVsSynchronizedMapPerformanceTest.java
+++ b/core-java-modules/core-java-collections-maps-3/src/test/java/com/baeldung/map/concurrenthashmap/PerformanceTest.java
@@ -11,7 +11,7 @@ import java.util.concurrent.TimeUnit;
 import org.junit.Assert;
 import org.junit.Test;
 
-public class ConcurrentHashMapVsSynchronizedMapPerformanceTest {
+public class PerformanceTest {
     
     public final static int THREAD_POOL_SIZE = 5;
     public final static int TEST_ITERATIONS = 5;