Added README.md

marker/README.md

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+---
+layout: pattern
+title: Marker Interface
+folder: marker
+permalink: /patterns/marker/
+categories: Design
+tags:
+ - Java
+ - Difficulty-Beginner
+---
+
+## Intent
+Using empy interfaces as markers to distinguish special treated objects.
+
+![alt text](./marker/etc/MarkerDiagram.png "Marker Interface")
+
+## Applicability
+Use the Marker Interface pattern when
+
+* you want to identify the special objects from normal objects
+* define a type that is implemented by instances of the marked class, marker annotations can not do that
+
+## Real world examples
+
+* [javase.7.docs.api.java.io.Serializable](https://docs.oracle.com/javase/7/docs/api/java/io/Serializable.html)
+* [javase.7.docs.api.java.lang.Cloneable](https://docs.oracle.com/javase/7/docs/api/java/lang/Cloneable.html)
+
+## Credits
+
+* [Effective Java 2nd Edition by Joshua Bloch](https://www.amazon.com/Effective-Java-2nd-Joshua-Bloch/dp/0321356683)