diff --git a/spring-5/src/main/java/com/baeldung/assertions/Car.java b/spring-5/src/main/java/com/baeldung/assertions/Car.java
index 4e210dfaab..abff27f0b0 100644
--- a/spring-5/src/main/java/com/baeldung/assertions/Car.java
+++ b/spring-5/src/main/java/com/baeldung/assertions/Car.java
@@ -39,8 +39,8 @@ public class Car {
         // ...
     }
 
-    public void сhangeOilWithIsNull(String oil) {
-        Assert.isNull(oil, "oil must be null");
+    public void replaceBattery(CarBattery carBattery) {
+        Assert.isNull(carBattery.getCharge(), "to replace battery the charge must be null");
         // ...
     }
 
@@ -99,7 +99,9 @@ public class Car {
         car.fuel();
 
         car.сhangeOil("oil");
-        car.сhangeOilWithIsNull(null);
+        
+        CarBattery carBattery = new CarBattery();
+        car.replaceBattery(carBattery);
 
         car.сhangeEngine(new ToyotaEngine());
 
diff --git a/spring-5/src/main/java/com/baeldung/assertions/CarBattery.java b/spring-5/src/main/java/com/baeldung/assertions/CarBattery.java
new file mode 100644
index 0000000000..a75457a7ec
--- /dev/null
+++ b/spring-5/src/main/java/com/baeldung/assertions/CarBattery.java
@@ -0,0 +1,13 @@
+package com.baeldung.assertions;
+
+public class CarBattery {
+    private String charge;
+
+    public String getCharge() {
+        return charge;
+    }
+
+    public void setCharge(String charge) {
+        this.charge = charge;
+    }
+}