Introduction:

Design patterns are reusable solutions to common programming problems. They are a way to organize and structure code, making it more maintainable and scalable. In this blog, we will cover some of the most popular design patterns in Java, organized into different categories for easy understanding. We will learn about the most important and famous patterns in the next blog.

Creational Patterns:

Creational Design Patterns are design patterns that deal with object creation mechanisms, trying to create objects in a manner suitable to the situation.

There are several Creational Design Patterns including:

1. Singleton Pattern: Ensures that a class has only one instance while providing a global access point to this instance.

2. Factory Pattern: Provides a way to create objects without specifying the exact class of object that will be created.

3. Builder Pattern: Separates the construction of a complex object from its representation, allowing the same construction process to create different representations.

4. Abstract Factory: Provide an interface for creating families of related or dependent objects without specifying their concrete classes.

5. Prototype: A fully initialized instance to be copied or cloned.

6. Object Pool: objects that are expensive to create are reused instead of created.

In short, Creational Design Patterns are design patterns that deal with object creation mechanisms, trying to create objects in a manner suitable to the situation. These patterns provide a way to create objects while hiding the creation logic, rather than instantiating objects directly using a new operator. They also separate the process of creating an object from the process of using an object.

Structural Patterns:

Structural patterns are design patterns that deal with class and object composition, creating relationships between objects to form larger structures. These patterns are used to form relationships between objects, rather than creating the objects themselves.

There are several Structural Design Patterns including:

1. Adapter: Allows classes with incompatible interfaces to work together by wrapping its interface around that of an already existing class.

2. Bridge: Separates an object's interface from its implementation, so the two can vary independently.

3. Composite: A tree structure of simple and composite objects, allows clients to treat individual objects and compositions uniformly.

4. Decorator: Dynamically adds/overrides behaviour in an individual object, similar to subclassing.

5. Facade: Provides a simplified interface to a complex subsystem.

6. Flyweight: A fine-grained instance used for efficient sharing, to support large numbers of similar objects efficiently.

7. Proxy: An object representing another object, used to control access to it.

In short, Structural Design Patterns are design patterns that deal with object composition, creating relationships between objects to form larger structures. These patterns provide a way to compose objects and classes into larger structures while keeping the structures flexible and efficient. They also provide a way to add new behaviours to existing objects, without modifying their classes.

Behavioural Patterns:

Behavioural patterns are design patterns that deal with communication between objects, and how objects interact and distribute responsibilities among themselves. These patterns are used to describe patterns of communication between objects, and how to structure communication to ensure that objects remain loosely coupled and that the pattern is easy to extend and maintain.

There are several Behavioral Design Patterns including:

1. Chain of Responsibility: A way of passing a request sequentially along a dynamic chain of receivers.

2. Command: Encapsulates a request as an object, thereby letting you pass requests as a method argument.

3. Interpreter: A way to include language elements in a program, to match the grammar of the programming language.

4. Iterator: Sequentially access the elements of a collection, without exposing its underlying representation.

5. Mediator: Defines simplified communication between classes to prevent a group of classes from referring explicitly to each other.

6. Memento: Capture and restore an object's internal state, without violating encapsulation, to allow for undo/redo.

7. Observer: A way of notifying change to several classes, to be notified of changes to the subject they are observing.

8. State: Alters an object's behaviour when its state changes, as if it had affected the object's class.

9. Strategy: Encapsulates an algorithm inside a class, hiding the implementation from clients.

10. Template Method: Defer the exact steps of an algorithm to a subclass, allowing for the algorithm's steps to be overridden.

11. Visitor: Represent an operation to be performed on the elements of an object structure, allowing for a new operation to be defined without changing the classes of the elements on which it operates.

12. Null Object: Designed to act as a default value of an object

In short, Behavioral Design Patterns are design patterns that deal with communication between objects and how objects interact and distribute responsibilities among themselves. These patterns describe patterns of communication between objects and how to structure communication to ensure that objects remain loosely coupled and the pattern is easy to extend and maintain.

Conclusion:

In summary, design patterns are a powerful tool for developers to solve common programming problems in a structured and organized way. By understanding and applying these patterns, developers can write more maintainable and scalable code.
We look at each of these design patterns in detail in upcoming blogs.