Design patterns are reusable approaches to common programming challenges. These provide a way to organize and structure code, making it more readable, maintainable, and reusable. Understanding these design patterns for object-oriented programming is crucial for producing well-designed, effective software because object-oriented programming is the foundation of many contemporary software systems.
So, whether you’re working on a new app or trying to refactor an existing one, this post is a must-read for any object-oriented programmer. We hope you’ll find it informative and engaging, and that it helps you to write better, more solid code that can withstand the test of time in production. By the end of this post, you’ll have a solid understanding of the most essential design patterns for object-oriented programming, and you’ll be able to apply them to your own projects. So, let’s get started and dive into the world of design patterns!
Best Design Patterns for Object-Oriented Programming
The most important design patterns for object-oriented programming will be covered, along with the underlying principles and code examples. This article will help you gain a deeper understanding of the ideas that underpin efficient Java object-oriented programming, whether you’re an expert or just looking to learn more.
1. DRY (Don’t repeat yourself)
DRY, an acronym for Don’t Repeat Yourself, is a design principle that encourages the elimination of pointless code and data. Every block of code or logic is supposed to have a single, clear representation in the system. Programmers can write code that is more scalable, less prone to bugs, and easier to maintain by adhering to this rule.
The advantage of this maintenance-focused object-oriented design principle. Duplication is for functionality, not code, so it’s important not to abuse it.
2. Open-Closed Design Principle
The Open-Closed Design Principle is a fundamental concept in Object-Oriented Programming (OOP) that states that software entities (classes, modules, functions, etc.) should be open for extension but closed for modification.
An example of Java code that deviates from the programming principle of open-closed design is given below.
In this code, GraphicEditor and Shape are inextricably linked; to create a new Shape, you must change an established system inside the thedrawShape(Shape s) method, which is both risky and undesirable.
3. Single Responsibility Principle (SRP)
The Single Responsibility Principle (SRP) is a design principle in object-oriented programming that states that every class should have a single responsibility, which should be encapsulated by the class.
This principle helps to promote the separation of concerns and makes it easier to maintain and modify code, as changes to one responsibility do not affect other responsibilities. The SRP is one of the five SOLID principles of object-oriented design and helps to create maintainable and scalable code.
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4. Dependency Injection or Inversion Principle
The Dependency Inversion Principle (DIP) or Inversion of Control (IoC) is a design principle for object-oriented programming that states that high-level modules should not depend on low-level modules, but instead, both should depend on abstractions.
Dependency Injection is a design pattern that implements the DIP by providing instances of the required objects to a class instead of the class creating them itself.
The Java Dependency Inversion Principle, or DIP, is violated in the following code sample:
As you can see, EventLogWriter, which is integrally connected to AppManager, is a requirement for AppManager. The AppManager class must be modified if you want to use another method of notifying your client, such as sending push notifications, SMS, or emails.
The Dependency Inversion Principle can be used to solve this issue so that the framework will provide or inject EventLogWriter into AppManager rather than AppManager having to request it.
5. Liskov Substitution Principle (LSP)
The Liskov Substitution Principle (LSP) is one of the best design patterns for object-oriented programming. According to this, objects from a superclass should be able to be swapped out for objects from a subclass without affecting the program’s correctness. The LSP is based on the idea of subtype polymorphism, where objects of a derived class can be treated as objects of the base class.
The following Java code demonstrates how to break the Liskov Substitution Principle:
If you have a method area(Rectangle r) that determines the area of the rectangle, the code will fail if you pass a square because a square is not a true rectangle.
It’s important because it helps to promote code reuse and maintainability. By ensuring that subclasses can be substituted for their base class, a developer can create a flexible system that can be easily extended and modified without affecting existing code. This makes it easier to add new functionality and respond to changing requirements, and it helps to prevent unexpected behavior and bugs in the code.
6. Interface Segregation Principle (ISP)
The Interface Segregation Principle (ISP) is a design pattern in object-oriented programming that states that clients should not be forced to depend on methods they do not use. The ISP design pattern states that a class should not be required to implement methods that are not relevant to its functionality.
This design pattern helps to promote modularity and maintainability in software development. By breaking down a large interface into smaller, more specific interfaces, the code becomes more flexible and easier to maintain. This ISP design pattern also makes it easier to add new functionality to a class.
7. Delegation Principles
Delegation is a principle in object-oriented programming that involves passing responsibilities from one object to another. This is achieved by having one object delegate a task to another object that is better equipped to handle it. Delegation is a way of composing objects to create complex systems in a modular and maintainable way.
To use the delegation principle effectively, it is important to keep the interfaces between the delegating and delegate objects well-defined and to ensure that the delegate object is only responsible for performing the task that it was designed to perform.
Final Thoughts
Design patterns are tried-and-true fixes for typical issues with software development. In object-oriented programming, design patterns provide a way to structure and organize code in a modular and maintainable way. They are a powerful tool for developers, helping to make code more flexible, reusable, and maintainable.
The selection of a design pattern is based on the particular requirements of a project because design patterns are not a one-size-fits-all solution. By understanding the different types of design patterns, developers can make informed decisions about which patterns to use and create software that is robust, scalable, and maintainable.
