From c6d114bf5b0606637e6b2ebdfc0d48a276ed14fc Mon Sep 17 00:00:00 2001
From: Wojciech Nagrodzki <278594+wnagrodzki@users.noreply.github.com>
Date: Sat, 4 Aug 2018 19:54:57 +0200
Subject: [PATCH] Added "Controlling subclassing behavior" section

---
 README.md | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/README.md b/README.md
index 35c7eb1..80e7c56 100644
--- a/README.md
+++ b/README.md
@@ -6,3 +6,13 @@
 
 If a method is independent of instance state it should be declared as type method, preferably by using `static` keyword (or `class` in case when the method is designed to be overridden in a subclass).
 > This is to avoid methods giving a false impression that they are dependent on the instance state while in fact they are not.
+
+### Controlling subclassing behavior
+
+Subclassing behavior should be designed with maximal hermetization principle in mind - choosing most restrictive access level possible.
+
+Declare class `final` unless you explicitly design it to be inheritable. For non final class declare all instance members as `final` and type members as `static` except for those you explicitly design for overriding. 
+
+When designing a module prefer `public` for non final class unless you explicitly design it to be inheritable by external clients. For `open` class prefer `public` for members except for those you explicitly design for overriding by external clients.
+
+> Every point that can be overridden increases complexity, thus it should always be a conscious choice to add it.