Design Patterns in Java: Introduction to Creational Design Patterns

Design patterns are essential tools for any software developer. They provide proven solutions to common problems, making your code more efficient, flexible, and reusable. In this blog, we’ll dive into the world of Design Patterns and focus on Creational Design Patterns with a practical example. Whether you're a beginner or an experienced developer, this guide will help you understand why and how to use design patterns in your Java projects.

What Are Design Patterns?

Design patterns are categorized into three types:

1. Creational Design Patterns: Deal with object creation mechanisms.

2. Structural Design Patterns: Deal with object composition and structure.

3. Behavioral Design Patterns: Deal with object interaction and responsibility.

Why Use Design Patterns?

• Efficiency: Solve common problems with proven solutions.

• Flexibility: Make your code adaptable to changes.

• Reusability: Write code that can be reused across projects.

Design patterns are not ready-to-use code; they are templates or blueprints that guide you on how to solve a problem.

Creational Design Patterns: Managing Object Creation

As your application grows, managing object creation becomes challenging. Initially, you might put all your logic into one class, but this can lead to tightly coupled code, making it difficult to maintain and extend. Creational design patterns help you manage this complexity by decoupling the object creation logic from the main logic.

Example: Invoice Management System

Let’s say you’re building an application to manage invoices for a store. Initially, you might create a single Invoice class with all the logic inside it.

public class Invoice {
    private String id;
    private double amount;

    public Invoice(String id, double amount) {
        this.id = id;
        this.amount = amount;
    }

    // Other methods for invoice logic
}

Later, you might need to create different types of invoices, such as:

• Tax Invoice

• Proforma Invoice

• Credit Invoice

If you keep adding constructors or modifying the Invoice class, your code will become tightly coupled and hard to maintain. This is where Creational Design Patterns come into play.

Problem: Tightly Coupled Code

Imagine you need to create different types of invoices with different constructors:

Invoice taxInvoice = new Invoice("TAX123", 1000, "TAX");
Invoice proformaInvoice = new Invoice("PRO456", 500, "PROFORMA");

If you decide to change the constructor later, you’ll need to update every part of your code where the Invoice class is instantiated. This is not scalable or maintainable.

Solution: Creational Design Patterns

Creational design patterns provide a way to decouple the object creation logic from the main logic.

Types Of Creational Design Patterns

Creational Design patterns are categorized into five types:

1. Builder Design Pattern

2. Singleton Design Pattern

3. Prototype Design Pattern

4. Factory Design Pattern

5. Abstract Factories