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null-object/README.md

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+---
+layout: pattern
+title: Null Object
+folder: null-object
+permalink: /patterns/null-object/
+categories: Behavioral
+tags:
+ - Java
+ - Difficulty-Beginner
+---
+
+## Intent
+In most object-oriented languages, such as Java or C#, references
+may be null. These references need to be checked to ensure they are not null
+before invoking any methods, because methods typically cannot be invoked on
+null references. Instead of using a null reference to convey absence of an
+object (for instance, a non-existent customer), one uses an object which
+implements the expected interface, but whose method body is empty. The
+advantage of this approach over a working default implementation is that a Null
+Object is very predictable and has no side effects: it does nothing.
+
+![alt text](./etc/null-object.png "Null Object")
+
+## Applicability
+Use the Null Object pattern when
+
+* you want to avoid explicit null checks and keep the algorithm elegant and easy to read.
+
+## Credits
+* [Pattern Languages of Program Design](http://www.amazon.com/Pattern-Languages-Program-Design-Coplien/dp/0201607344/ref=sr_1_1)