Homework 4: Advanced Structural Patterns – Singleton & Adapter

This project demonstrates the implementation of two important structural design patterns in Java:

1. Singleton Pattern: Used to create a global configuration manager.
2. Adapter Pattern: Used to integrate a legacy chat service into a new system.

Project Structure

The project consists of the following classes:

Singleton Pattern

ConfigurationManager.java: Implements the Singleton pattern to manage global configuration settings. ConfigManagerDemo.java: Demonstrates the usage of the ConfigurationManager.

Adapter Pattern

LegacyChatService.java: Simulates a legacy chat service with its own interface. ChatService.java: Defines the new interface for chat services. ChatServiceAdapter.java: Adapts the legacy chat service to the new interface. ChatAdapterDemo.java: Demonstrates the usage of the ChatServiceAdapter.

Code Explanation

Singleton Pattern

ConfigurationManager:

Ensures only one instance of the configuration manager exists.

Loads default configurations (e.g., maxPlayers, defaultLanguage).

Provides methods to retrieve and print configurations.

ConfigManagerDemo:

Demonstrates how to use the ConfigurationManager to access and print configurations.

Adapter Pattern

LegacyChatService:

Simulates a legacy chat service with a method sendLegacyMessage.

ChatService:

Defines the new interface with a method sendMessage.

ChatServiceAdapter:

Implements the ChatService interface.

Adapts the sendMessage method to call the legacy sendLegacyMessage method.

ChatAdapterDemo:

Demonstrates how to use the ChatServiceAdapter to send a message through the legacy service.

Design Patterns Used Singleton Pattern Ensures a single instance of the ConfigurationManager exists.

Provides a global point of access to configuration settings.

Adapter Pattern Bridges the gap between the legacy LegacyChatService and the new ChatService interface.

Allows the legacy service to be used in a new system without modifying its code.

Testing

ConfigurationManager

The ConfigManagerDemo class tests the following:

Retrieval of configuration values (e.g., maxPlayers, defaultLanguage).

Printing all configuration settings.

ChatServiceAdapter

The ChatAdapterDemo class tests the following:

Sending a message through the adapter.

Verifying that the output matches the legacy format (Legacy Chat: ).

Code Quality

Single Responsibility Principle:

Each class has a single responsibility (e.g., ConfigurationManager manages configurations, ChatServiceAdapter adapts the legacy service).

Dependency Inversion Principle:

The ChatServiceAdapter depends on the ChatService interface, not concrete implementations.

Naming Conventions:

Class names use PascalCase (e.g., ConfigurationManager).

Method and variable names use camelCase (e.g., getConfig, sendMessage).