Update README.md

[skip ci]

Author: edizor

core-java-modules/core-java-lang-oop-others/README.md

@@ -6,3 +6,4 @@ This module contains articles about Object Oriented Programming (OOP) in Java
 - [Object-Oriented-Programming Concepts in Java](https://www.baeldung.com/java-oop)
 - [Static and Dynamic Binding in Java](https://www.baeldung.com/java-static-dynamic-binding)
 - [Pass-By-Value as a Parameter Passing Mechanism in Java](https://www.baeldung.com/java-pass-by-value-or-pass-by-reference)
+- [Check If All the Variables of an Object Are Null](https://www.baeldung.com/java-check-all-variables-object-null)