Null Object pattern

·         The null object pattern falls under Behavior design pattern

·         The object is null but your code can still run.

·         The use of Null Object pattern simplifies the client code and makes it less error prone.

·         The use of the Null Object pattern is that it doesn't require a null check to prevent a crash or error.

·         Consider an application which does orders based on the discount.

Below is the Order class:

[Code]

Let us say we have two types of discount “Premium discount “and “Festival discount”

[Code]

Now we can able to create Premium and Festival orders using Premium and Festival discount

Now let’s take an example where we need to create an order for customer who had no discount.

[Code]

Now the applications crashes

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We need to create a discount class which does NO discount calculation as shown in the below code.

[Code]

Now the below client call to order object would not crash.

[Code]

Reference : https://www.codeproject.com/Articles/1042674/NULL-Object-Design-Pattern