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Module 1: Builder Pattern

Module Overview

The Builder pattern is a creational design pattern that lets you construct complex objects step by step. It's particularly useful when you need to create an object with many possible configurations.

Learning Objectives

Know how to implement the Builder Pattern for Java classes
Know how to instantiate objects using an object builder
Know how to create Required fields using validation logic
Understand the advantages of the Builder Pattern
Understand being liberal in what your program accepts and conservative in what your program sends out

Key Topics

Builder Pattern Components

Builder interface and concrete builders
Director class
Product class
Fluent interface with method chaining

Resources

Practice Exercises

Implement a basic builder pattern
Create a complex object using the builder
Add validation to the builder
Implement a fluent interface

Next Steps

After completing this module:

Complete the practice exercises above
Review the additional resources for deeper understanding
Move on to Module 2 to learn about Class & Sequence Diagrams

Builder Pattern Explained

The Builder pattern is a creational design pattern that lets you construct complex objects step by step. It's particularly useful when constructing objects with many parameters, some of which may be optional.

Problem It Solves

Classes with many fields can have constructors with numerous parameters, making them difficult to use and read. Consider this example:

public TacoSalad(Tortilla tortilla, Lettuce lettuce, Meat meat, Rice rice, 
    Beans beans, Dressing dressing, Pico pico, TortillaChips tortillaChips, 
    Guacamole guacamole, boolean isGuacOnTheSide, SourCream sourCream, 
    boolean isSourCreamOnTheSide, Lime lime)

Builder Solution

The Builder pattern creates a separate builder class that:

Has methods to set each field individually
Returns the builder itself for method chaining
Provides a build() method that validates and creates the object

Code Example

TacoSalad tacoSalad = new TacoSalad.Builder()
    .withLettuce(romainLettuce)
    .withTortilla(flourTortilla)
    .withBeans(blackBeans)
    .withMeat(chicken)
    .withGuac(guac)
    .withGuacOnTheSide(true)
    .build();

Key Benefits

More readable code through method chaining
Easier to maintain when adding new fields
Validates required fields before object creation
Handles immutable objects elegantly
Makes constructors with many parameters manageable