11.2.1 - Creational Patterns
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Singleton Pattern
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Today, we're starting with the Singleton pattern. Can anyone tell me what a Singleton is?
Is it a pattern that restricts a class to a single instance?
Exactly! The Singleton pattern ensures that a class has only one instance. It can be very useful when orchestrating resources that should only have a single point of access, like a configuration manager or logger. A common mnemonic is 'Save One', emphasizing its principle of singularity.
Can you show us how it's implemented?
"Certainly! Here's a quick code snippet...
Factory Method Pattern
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Next up is the Factory Method Pattern. Who can explain its purpose?
Doesn't it allow subclasses to alter the types of objects created?
Exactly right! The Factory Method defines an interface for creating objects but lets subclasses decide which class to instantiate. A good way to remember this is 'Factory Flexibility'.
Could you show us an example?
"Of course! Here’s how it’s implemented...
Abstract Factory Pattern
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Now let’s discuss the Abstract Factory Pattern. What do we aim to achieve with it?
Is it about creating families of related objects?
Exactly! The Abstract Factory provides an interface for creating families of related or dependent objects without specifying their concrete classes. A mnemonic is 'Family Factory'.
Can we see an implementation?
"Sure! Here’s a simple implementation...
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
Creational patterns are crucial in software design, as they provide methods to create objects in a controlled manner. This section introduces key creational patterns, including the Singleton, Factory Method, Abstract Factory, Builder, and Prototype patterns, each with its specific application and implementation in Java.
Detailed
Creational Patterns in Java
Creational patterns are a subset of design patterns dedicated to the creation of objects in software applications. These patterns are designed to abstract the instantiation process, providing various means for creating objects, which can help promote system flexibility and ease of maintenance. By using creational patterns, developers can manage the complexities and variations that arise when creating object instances.
In Java, the following key creational patterns are discussed:
- Singleton Pattern: Ensures a class can only have one instance and provides a global access point to that instance. This is especially useful for managing shared resources like database connections or logging.
- Factory Method Pattern: Defines an interface for creating objects and allows subclasses to alter the type of created objects. This pattern encourages loose coupling in the code.
- Abstract Factory Pattern: Provides an interface for creating families of related or dependent objects without specifying their concrete classes. It's useful for creating variations of products.
- Builder Pattern: Facilitates the step-by-step construction of complex objects. It’s particularly effective for objects with many parameters.
- Prototype Pattern: Used to create duplicate objects while keeping performance in mind, allowing for easy replication of objects while maintaining their original structure.
Understanding and implementing these creational patterns effectively enhances code modularity, readability, and maintainability, aligning with best practices in software development.
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Key Concepts
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Singleton Pattern: Ensures only one instance of a class exists.
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Factory Method Pattern: Allows subclasses to determine what type of object to create.
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Abstract Factory Pattern: Facilitates the creation of related or dependent objects without specified class instances.
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Builder Pattern: Constructs complex objects step-by-step.
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Prototype Pattern: Copies existing objects to create new instances efficiently.
Examples & Applications
A typical use case for the Singleton pattern is a Logger that should only have one instance throughout the application.
The Factory Method pattern can be utilized in a GUI framework to decide the type of UI element to create based on user input.
The Builder pattern is ideal for constructing a Computer object with various configurations, allowing gradual assembly of its components.
The Abstract Factory is employed in a mobile application to create elements for both Android and iOS without changing the client code.
Memory Aids
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Rhymes
In a factory, shapes rubber stamp, Made unique, no instance cramp, One Singleton, sharp and smooth, A pattern that makes the code improve.
Stories
Imagine a world with only one sun—a Singleton. Just like a sculptor who can mold different shapes, Factory Methods let you shape your designs, creating what you need at a moment's notice, keeping everything related neatly in an Abstract Factory factory… just like a family of tools!
Memory Tools
Remember C, F, A, B, P: 'Cats Find Ants Before Pests'. It stands for Creational Patterns: Constructor, Factory, Abstract Factory, Builder, Protocol.
Acronyms
Use the acronym 'FAB P' for Factory, Abstract Factory, Builder, and Prototype. Highlighting the focus on the object creation.
Flash Cards
Glossary
- Creational Patterns
Design patterns focused on object creation processes, promoting flexibility and control.
- Singleton Pattern
A pattern ensuring a class has only one instance and providing a global access point.
- Factory Method Pattern
Defines an interface for creating an object, allowing subclasses to modify the type of created objects.
- Abstract Factory Pattern
Provides an interface to create families of related or dependent objects without needing to specify concrete classes.
- Builder Pattern
A pattern that allows for constructing complex objects step by step.
- Prototype Pattern
A pattern for creating duplicate objects while avoiding costly operations.
Reference links
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