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README.md

Builder Pattern

Introduction

Builder is a creational design pattern that allows constructing complex objects step by step.

Separate the construction of a complex object from its representation so that the same construction process can create different representations.

Source: Design Patterns: Elements of Reusable Object-Oriented Software

The Problem

Imagine we have a complex object with a lot of fields. Let's say we have a Person with 8 fields. While creating a Person object we can use constructor to populate these fields. This counstructor would end up by 8 parameters which is a bad practice, plus number of parameters will keep on growing while adding new options in the future. This is called telescoping constructor anti pattern.

When to use this pattern?

  • When you have a "telescoping" constructor (with more than 7 parameters)
  • When you need to construct object step by step

Known uses

  • java.lang.StringBuilder
  • java.lang.StringBuffer