Design Patterns Null Object Pattern - Design Patterns

What is Design Patterns Null Object Pattern?

In Null Object pattern, a null object replaces check of NULL object instance. In its place of putting if check for a null value, Null Object reflects a do not anything relationship. Such Null object can also be used to provide default behaviour in case data is not accessible.

In Null Object pattern, we construct an abstract class specify different operations to be done, concrete classes extending this class and a null object class provide do nothing implementation of this class and will be used seamlessly where we need to verify null value.

Implementation

We are going to produce conceptual Customer conceptual class essential operations. Here the name of the customer and concrete classes extending the Abstract Customer class. A factory class Customer Factory is produced to return either Real Customer or Null Customer objects based on the name of client passed to it.
NullPatternDemo, our demo class, will use Customer Factory to show the use of Null Object pattern.
null_pattern_uml_diagram

Step 1

Create an abstract class.

AbstractCustomer.java

Step 2

Create concrete classes extending the above class.

RealCustomer.java

NullCustomer.java

Step 3

Create Customer Factory Class.

CustomerFactory.java

Step 4

Use the Customer Factory to get each Real Customer or Null Customer substance based on the name of client passed to it.

NullPatternDemo.java

Step 5

Verify the output.

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