Top 5 Java Design Patterns Every Developer Should Know

Are you planning to become a Java developer? If yes, then the following post is worth the read. It emphasizes what design patterns are, why there is a need for design patterns, the types of design patterns, and the top 5 Java design patterns every Java developer must know.

What are Design Patterns?

Design patterns are general solutions that work wonders on routine problems that arise while designing software. Every pattern acts as a blueprint that enables customization so that professionals can easily solve any kind of design problem that has been raised while developing different software modules.

Technically speaking design patterns are generic repeatable solutions that can aid frequently arising problems in a software design. In other words, a software design pattern is more like a software template that is highly recommended for solving any problem that occurs in different instances while designing any kind of software application or framework. It may quite interest you to know that Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides were the authors of the book on Java design patterns.

Why is there a need for Design Patterns in the first place?

As mentioned above, design patterns tend to solve multiple development-related problems. In addition to that, they can simplify coding procedures, enhance code maintainability, and promote code reuse. In addition to all that, Java developers who are well-acquainted with the usage of design patterns can write efficient, scalable, and adaptable code. Design patterns are the most common vocab used to discuss software solutions.

Now tell me which is your favorite dish? Have you ever wondered what’s so loving about that dish? Of course, the experienced cook, be it your mom or your favorite restaurant chef, must be using some specific ingredient or way to come up with such a lip-smacking meal. Similarly, design patterns are some of the best approaches considered by the GOF to come up with the best possible results.

Design patterns are one of the best practices in Java used by object-oriented developers to ensure the best possible solution over a substantial period. Now many of you have this misconception that design patterns solve problems automatically which is not the case, these assist in solving the problem.

Benefits of Considering Design Patterns

• It makes code reusable

• Speeds up the development process

• Changes or any modifications are possible

• Common problems faced by Java developers are successfully eliminated

• Enhance object-oriented skill

• Easy to understand the flow of code

• Less code

• Easy to maintain

So isn’t it obvious that design patterns are mainly used to accelerate development procedures? Not only that, it offers proven development paradigms, which substantially save time without even reinventing patterns every time a problem arises.

Now since design patterns are meant to fix all the known problems, it becomes pretty easy for developers to predict them quite in advance, maybe during the implementation of such procedures. Also, as a developer, one must know that design patterns are highly recommended when moving from the analysis model to the development model.

Types of Design Patterns

1. Creational

Creational design patterns tend to provide a wide range of object creation mechanisms which tends to increase the flexibility and reuse of the existing code. Its ultimate objective is to offer precise solutions in the best possible manner. This is how!

• Singleton - Now this creational design pattern certainly enables developers to ensure that the entire class has one instance that has a global access point. It works on “One and Only One instance”.

Public class SingletonClass {

private static SingletonClass instance;

private SingletonClass() {

// private constructor to prevent instantiation from outside

}

public static SingletonClass getInstance() {

if (instance == null) {

instance = new SingletonClass();

}

return instance;

}

}

And

@RestController

@RequestMapping("/api")

public class SingletonController {

private SingletonClass singletonClass;

public SingletonController(SingletonClass singletonClass) {

this.singletonClass = singletonClass;

}

@GetMapping("/singleton")

public String getSingleton() {

return "This is a singleton instance: " + singletonClass.toString();

}

}

So what happens here is a single database object is shared by different parts of the program.

• Factory - The Factory method is another creational design pattern that offers a solution to develop product objects hassle-free. Here there is no need to specify concrete classes during the creation process.

Public interface PaymentProcessor {

void processPayment();

}

And

@Service

public class CreditCardPaymentProcessor implements PaymentProcessor {

@Override

public void processPayment() {

// Credit card payment transactions

}

}

@Service

public class PaypalPaymentProcessor implements PaymentProcessor {

@Override

public void processPayment() {

// Paypal card payment transactions

}

}

The factory method is used to converse system resources by reusing existing objects instead of reconstructing them on a repeated basis.

• Abstract Factory - The next interesting creational design pattern is an abstract factory which enables developers to produce families of related objects. Now do we need to specify concrete classes, guess not!

Sample in Java

//Factory Classes

public interface ProductFactory {

Product createProduct();

}

public class ProductAFactory implements ProductFactory{

@Override

public Product createProduct() {

return new ProductA();

}

}

public class ProductBFactory implements ProductFactory{

@Override

public Product createProduct() {

return new ProductB();

}

}
When to consider Abstract Factory? It’s when the code needs to deal with multiple groups of related items. Also, it enables you to keep room for adding more types in the future.

• Builder - The next creational design pattern is builder which enables you to construct complex objects seamlessly. Here with the help of the same construction code, different types and representations can be done.

Sample code for builder in Java

@Builder

@Getter

@Setter

public class Beer {

//required

private String name;

private double drinkSize;

private double alcoholPercentage;

private double price;

// Other attributes

private String brewery; // The brewery that produces the beer.

private String countryOfOrigin; // The country where the beer is originally from.

private String description; // A brief description of the beer's characteristics.

private String packaging; // The packaging type (bottle, can, draft, etc.).

private String servingTemperature; // The recommended serving temperature.

private String foodPairing; // Foods that pair well with this beer. }

So what is the point of doing all this is,

• Reduces the number of parameters in the constructor and offers readable method calls

• Enables object instantiation in a complete state

• Simplified the building process of immutable objects.

• Prototype - A prototype is a creational design pattern enabling the copying of all the existing objects and all this is possible without making the code dependent on their classes.

Sample in Java

design patterns

└── creational

└── prototype

├── controller

│ └── TreeController.java

├── model

│ ├── Tree.java

│ ├── PlasticTree.java

│ └── PineTree.java

└── PrototypeDemoApplication.java

Coding is like this

//Abstract Class

@Getter

@Setter

public abstract class Tree implements Cloneable {

private String type;

public abstract void copy();

@Override

protected Object clone() throws CloneNotSupportedException {

return super.clone();

}

}

//Concrete Class-1 Pine Tree

public class PineTree extends Tree {

public PineTree() {

setType("Pine Tree");

}

@Override

public void copy() {

//implementation

}

}

//Concrete Class-2 Plastic Tree

public PlasticTree() {

setType("Plastic Tree");

}

@Override

public void copy() {

//implementation

}

The prototype pattern should be taken into consideration when a new object is required to create exhibits only minor differences from an existing one.

2. Structural

Structural design pattern in Java enables seamless focus on the composition of classes or objects basically to form more large, complex, and complicated structures than ever before. Structural design patterns are highly recommended in organizing and managing relationships between objects to achieve great reusability, flexibility, maintainability, and solutions.

• Adapter - Now this method in particular enables developers to make two incompatible interfaces that work by developing a bridge between them.

• Composite - This design pattern method is used to compose objects into tree structures to represent part-whole hierarchies. With a Composite design pattern, it is possible to treat individual objects and the composition of objects. Also, clients now can work on different complex structures much like they would do with individual objects.

• Proxy - The next structural design pattern is proxy which acts as a clear substitute for an object. Now what the substitute does is it offers immediate or controlled access to the real object.

• Fly Weight - Another interesting structural design pattern mainly used to create lots and lots of objects of a class. Now every object tends to consume memory space which is quite important for low memory devices. The flyweight design pattern has the potential to reduce the load on memory by sharing objects.

• Facade - Facade offers a simplified, high-level interface to a set of interfaces ensuring easier for clients to interact with that subsystem.

• Bridge - This method allows developers to design separately an object’s abstraction from its implementation so that both can vary independently.

• Decorator - Lastly, this structural design pattern enables the addition of behavior to individual objects, in any way possible, be it statistically or dynamically. And all this is possible without hampering or affecting the behavior of other objects especially from the same class.

3. Behavioral

Now behavioral design patterns mainly have to deal with the communication and interaction between different objects and classes. It’s more like supervising how communication and interaction take place between these objects and classes. This is how objects and classes collaborate and communicate to complete different tasks and responsibilities.

• Template Method - Now this particular design pattern defines the skeleton of an algorithm in such a method enabling it to alter some steps of the algorithm without even changing the overall structure.

• Mediator - Mediator is such a design pattern that promotes loose coupling between objects by centralizing their communication through a mediator object. Instead of objects directly communicating with each other, they communicate through the mediator, which encapsulates the interaction and coordination logic.

• Observer - This particular design pattern focuses on one-to-many dependency between different objects. So what happens is when one object changes, all its dependents are equally notified and updated right then and there automatically.

• Strategy - Strategy is such kind of pattern that defines an entire family of algorithms, especially the ones that are encapsulated from within. They are so involved that interchanging is next to impossible. Also, the client can choose an appropriate algorithm during runtime.

• State - Here the object can alter its behavior when its internal state changes.

• Visitor - This design pattern should be taken into account when there is a set of structured, hierarchical objects on which different operations are performed and all this is done without modifying classes.

• Iterator - If there is a need for easy access to an aggregate object then the iterator method is worth considering.

• Memento - And lastly we have a Memento that ensures the safe and easy restoration of the previous state of an object without even showcasing details of its implementation.

Top 5 Design Patterns Every Java Developer Must Learn

#1 Factory Design Pattern

Factory design patterns are useful and well-known design patterns in Java. This one ensures better control over object creation procedures instead of the constructor. Now Factory design pattern is thoroughly based on the Encapsulation object-oriented concept. So what this means is that it is used to create different objects from the factory, often referred to as items, and it encapsulates the creation code to a great extent. One of the finest examples to consider here is the BorderFactory Class of Swing API.

#2 Decorator Design Pattern

The next design pattern to consider is the Decorator pattern which is highly considered for adding high-end functionality on objects at runtime. Now does it alter the interface? Of course not! It doesn’t alter the interface, here Java developers can add new functionalities with the help of composition.

#3 Adapter Design Pattern

The next design pattern that Java developers must be well-acquainted with is the Adapter design pattern. Mainly used to convert interfaces in such a way that two parties can work together seamlessly. If not done then due to incompatible interfaces, things can get pretty messed up.

#4 Proxy Design Pattern

The next design pattern is the proxy design pattern. This is another alluring design pattern that enables one to have control over an object due to a wide range of reasons such as security, performance, caching, and whatnot! Proxy design patterns are more like real objects so they can even act as surrogates, until and unless the real object is available. Once it's available, it can forward requests to real ones for further processing.

#5 Strategy Design Pattern

The next one in line is the strategy design pattern. This one successfully encapsulates interchangeable behaviors and makes seamless use of algorithms and delegation. Now strategy design pattern is thoroughly based on Open closed design principle which means it is possible to promote how to write extensible code without touching all the tried and tested codes.

Overview:

So that’s all for now! These are some of the best object-oriented design patterns to take into consideration.

• Java Patterns are designed to be reusable

• They define system architecture with ease

• Design patterns ensure pure transparency

• Testified and well-proven solutions

• Design Pattern clarity to the System Architecture and provide the possibility of building a better system.