Merge pull request #14522 from edizor/master

Update README

core-java-modules/core-java-collections-maps-6/README.md

@@ -5,3 +5,4 @@
 - [Converting Object To Map in Java](https://www.baeldung.com/java-convert-object-to-map)
 - [Difference Between Map.clear() and Instantiating a New Map](https://www.baeldung.com/java-map-clear-vs-new-map)
 - [Converting JsonNode Object to Map](https://www.baeldung.com/jackson-jsonnode-map)
+- [How to Modify a Key in a HashMap?](https://www.baeldung.com/java-hashmap-modify-key)

core-java-modules/core-java-date-operations-3/README.md

@@ -9,4 +9,5 @@ This module contains articles about date operations in Java.
 - [Adding One Month to Current Date in Java](https://www.baeldung.com/java-adding-one-month-to-current-date)
 - [How to Get Last Day of a Month in Java](https://www.baeldung.com/java-last-day-month)
 - [Getting Yesterday’s Date in Java](https://www.baeldung.com/java-find-yesterdays-date)
+- [How to Get the Start and End Dates of a Year Using Java](https://www.baeldung.com/java-date-year-start-end)
 - [[<-- Prev]](/core-java-modules/core-java-date-operations-2)

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

@@ -7,3 +7,4 @@ This module contains articles about Object Oriented Programming (OOP) in Java
 - [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)
+- [Law of Demeter in Java](https://www.baeldung.com/java-demeter-law)

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

@@ -10,3 +10,4 @@ This module contains articles about Object-oriented programming (OOP) patterns i
 - [Using an Interface vs. Abstract Class in Java](https://www.baeldung.com/java-interface-vs-abstract-class)
 - [Should We Create an Interface for Only One Implementation?](https://www.baeldung.com/java-interface-single-implementation)
 - [How to Deep Copy an ArrayList in Java](https://www.baeldung.com/java-arraylist-deep-copy)
+- [Stateless Object in Java](https://www.baeldung.com/java-stateless-object)

core-java-modules/core-java-networking-4/README.md

@@ -4,3 +4,4 @@
 - [Validating IPv4 Address in Java](https://www.baeldung.com/java-validate-ipv4-address)
 - [Download a Webpage in Java](https://www.baeldung.com/java-download-webpage)
 - [URL Query Manipulation in Java](https://www.baeldung.com/java-url-query-manipulation)
+- [Understanding the java.net.SocketException Broken Pipe Error](https://www.baeldung.com/java-socketexception-broken-pipe-error)

core-java-modules/core-java-string-operations-6/README.md

@@ -9,3 +9,4 @@
 - [Split a String Into Digit and Non-Digit Substrings](https://www.baeldung.com/java-split-string-digits-letters)
 - [Check if a String Contains Non-Alphanumeric Characters](https://www.baeldung.com/java-string-test-special-characters)
 - [Check if a String Has All Unique Characters in Java](https://www.baeldung.com/java-check-string-all-unique-chars)
+- [Performance Comparison Between Different Java String Concatenation Methods](https://www.baeldung.com/java-string-concatenation-methods)