The builder pattern is a software design pattern. The intention is to abstract steps of construction of objects so that different implementations of these steps can construct different representations of objects. In this article, we look into the implementation of builder pattern in Java with UML diagram as well its real life example.
Builder Pattern vs Factory method pattern
This is the general question or doubt we usually face when we have to decide when to use factory method pattern and builder pattern. If you need to refresh your concept of factory method pattern, check my post on Factory pattern .
A factory is simply a wrapper function around the constructor. The principle difference is that a factory method pattern require the entire object to be built in a single call, will all the parameters pass in on a single line. Then final object will be return.
A real life example can be “meal of the day” in a restaurant. The creation of the meal is a factory pattern, because you tell the kitchen get me the meal of today and the kitchen decide what object to generate based on the hidden criteria.
A builder pattern, whereas is a wrapper object around all the possible parameters you might want to pass to a constructor. This allows you to use setter method to build your own parameter list.
A real life example appears if you order a custom pizza ( any drink). In this case, waiter tell the chef ( TeaBuilder, CoffeeBuilder in our example, you will see soon) I need a pizza; add extra cheese, olives, and corn to it. Therefore, the builder exposes the attributes the generated object should have, but hide how to set them.
The Builder is only needed when an object cannot be produced in one step.
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