Update readme.md

sealed_class/readme.md

@@ -1,9 +1,23 @@
 ## Sealed class
-Subclasses of a sealed class must be modified by one of the following:
 
-  - final: No further subclasses are allowed.
-    ![final]()
-  - sealed: A sealed set of subclasses is allowed.
-  - non-sealed: This is a new keyword that allows inheritance by unknown subclasses.
-    ![non-sealed]()
+A sealed class MUST permit at least one subclass
+  ![sealed_class_must_contain_at_leat_one_subclass](https://github.com/HunorVadaszPerhat/java_lang_specs/blob/main/images/sealed_class_must_contain_subclass.png)
+
+A subclasses must be either final, non-sealed or sealed
+  ![sealed_class_rule_1](https://github.com/HunorVadaszPerhat/java_lang_specs/blob/main/images/sealed_class_rules_1.png)
+
+  - a subclass as non-sealed
+    ![sealed_class_rule_2](https://github.com/HunorVadaszPerhat/java_lang_specs/blob/main/images/sealed_class_rule_2.png)
+  - a subclass as final
+    ![sealed_class_rule_3](https://github.com/HunorVadaszPerhat/java_lang_specs/blob/main/images/sealed_class_rule_3.png)
+  - a subclass as sealed must have subclasses
+    ![sealed_class_rule_4](https://github.com/HunorVadaszPerhat/java_lang_specs/blob/main/images/sealed_class_rule_4.png)
+    - if subclass is non-sealed
+      ![sealed_class_rule_5](https://github.com/HunorVadaszPerhat/java_lang_specs/blob/main/images/sealed_class_rule_5.png)
+    - if subclass is final
+      ![sealed_class_rule_6](https://github.com/HunorVadaszPerhat/java_lang_specs/blob/main/images/sealed_class_rule_6.png)
+
+
+
+