Design patterns are reusable solutions to common software design problems. In Java, they are categorized broadly into three main types:
-
Creational Design Patterns
Focus: Object creation mechanisms to create objects in a way that is suitable for the situation.- Help make the system independent of how objects are created, composed, and represented.
- Key idea: Control object creation to ensure flexibility and reuse.
Examples:
- Singleton
- Factory Method
- Abstract Factory
- Builder
- Prototype
-
Structural Design Patterns
Focus: Class and object composition to form larger structures.- Help ensure that different parts of a system work together in a flexible and efficient way.
- Key idea: Simplify relationships between objects or combine them for new functionality.
Examples:
- Adapter
- Bridge
- Composite
- Decorator
- Facade
- Flyweight
- Proxy
-
Behavioral Design Patterns
Focus: Interaction and communication between objects.- Help define how objects interact, how responsibilities are distributed, and how workflows are controlled.
- Key idea: Streamline complex communication between objects.
Examples:
- Chain of Responsibility
- Command
- Interpreter
- Iterator
- Mediator
- Memento
- Observer
- State
- Strategy
- Template Method
- Visitor
- Creational Patterns: Think of building a house. You decide how to construct it: blueprint (Prototype), modular pieces (Builder), or hiring a factory (Factory Method).
- Structural Patterns: Consider how you connect rooms: walls (Adapter), open spaces (Bridge), or fancy decorations (Decorator).
- Behavioral Patterns: It’s about how people in the house interact: assigning tasks (Command), following workflows (Template Method), or broadcasting news (Observer).