Update README.md

Author: johnA1331

libraries-6/README.md

@@ -17,4 +17,5 @@ Remember, for advanced libraries like [Jackson](/jackson) and [JUnit](/testing-m
 - [Introduction to Protonpack](https://www.baeldung.com/java-protonpack)
 - [Java-R Integration](https://www.baeldung.com/java-r-integration)
 - [Using libphonenumber to Validate Phone Numbers](https://www.baeldung.com/java-libphonenumber)
+- [Apache Commons Collections vs Google Guava](https://www.baeldung.com/apache-commons-collections-vs-guava)
 - More articles [[<-- prev]](/libraries-5)