knowledge/technology/dev/programming/patterns/creational/Builder Pattern.md

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Builder Pattern

Description:

The Builder Pattern is a creational design pattern used to construct a complex object step by step. It separates the construction of an object from its representation, allowing you to create different variations of the same object with a clear and consistent API. This pattern is particularly useful when an object has many optional components or configuration settings.

How it's Used:

1. Builder Interface: Define an abstract builder interface that declares methods for constructing different parts of the complex object. These methods should cover all possible configurations.
2. Concrete Builders: Create concrete builder classes that implement the builder interface. Each concrete builder is responsible for building a specific variant of the complex object.
3. Product: Define the complex object (the product) that you want to create. This object should have a way to accept values or components set by the builder.
4. Director (Optional): You can create a director class (optional) that orchestrates the construction process using a specific builder. The director simplifies client code by providing a higher-level interface to construct the object.
5. Client Code: In your application, use the builder to construct the complex object step by step. You can chain method calls together for a more fluent and readable construction process.

Example:

Consider building a Computer object with various optional components such as a processor, memory, storage, and graphics card. Here's how the Builder Pattern can be applied:

• Builder Interface: Define an ComputerBuilder interface with methods like setProcessor, setMemory, setStorage, and setGraphicsCard.
• Concrete Builders: Create concrete builder classes like GamingComputerBuilder and OfficeComputerBuilder, both implementing the ComputerBuilder interface. Each builder knows how to construct a specific type of computer.
• Product: Define the Computer class with fields for processor, memory, storage, and graphics card, and a constructor to initialize these fields.
• Director (Optional): Create a ComputerDirector class that takes a ComputerBuilder as a parameter. The director can provide higher-level methods like buildGamingComputer or buildOfficeComputer.
• Client Code: In your application, use the builder to construct a computer with the desired components:

ComputerBuilder builder = new GamingComputerBuilder();
Computer gamingComputer = builder.setMemory(16).buildComputer();