Update README.md

Author: lor6

core-java-lang/README.md

@@ -58,3 +58,4 @@
 - [Inheritance and Composition (Is-a vs Has-a relationship) in Java](http://www.baeldung.com/java-inheritance-composition)
 - [A Guide to Constructors in Java](https://www.baeldung.com/java-constructors)
 - [Retrieving a Class Name in Java](https://www.baeldung.com/java-class-name)
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