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javadesign-patternsbuilder

When would you use the Builder Pattern?

What are some common, real world examples of using the Builder Pattern? What does it buy you? Why not just use a Factory Pattern?

Solution

  • The key difference between a builder and factory IMHO, is that a builder is useful when you need to do lots of things to build an object. For example imagine a DOM. You have to create plenty of nodes and attributes to get your final object. A factory is used when the factory can easily create the entire object within one method call.

    One example of using a builder is a building an XML document, I've used this model when building HTML fragments for example I might have a Builder for building a specific type of table and it might have the following methods (parameters are not shown):

    BuildOrderHeaderRow()
BuildLineItemSubHeaderRow()
BuildOrderRow()
BuildLineItemSubRow()

    This builder would then spit out the HTML for me. This is much easier to read than walking through a large procedural method.

    Check out Builder Pattern on Wikipedia.