🚀 Java Space Invaders — Refactored with Design Patterns

A modern refactoring of the classic Java Space Invaders arcade game, enhanced using Creational, Structural, and Behavioral Software Design Patterns as part of the CCSW 413 — Software Design Patterns course at the University of Jeddah.

This project improves the original game’s architecture by making it modular, extensible, memory-efficient, and easier to maintain, while preserving the original gameplay experience.

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🎮 Project Overview

This application is based on the iconic Space Invaders (1978) game.
The player controls a cannon and defends Earth from waves of alien invaders.

To elevate the code quality and architecture, we applied the following design patterns across three phases:

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1. Creational Design Patterns

Prototype

• Used for cloning Alien objects instead of repeatedly instantiating new ones.
• Reduces redundancy and simplifies creation of multiple similar aliens.

Factory Method

• Introduced a BoardFactory to handle creation of game elements (player, aliens, bullets).
• Decouples object creation from the game logic.

Singleton

• Implemented SpriteManager to cache and reuse sprite images.
• Ensures each sprite is loaded once → memory and performance optimization.

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2. Structural Design Patterns

Decorator

• Created AlienDecorator and StrongAlien to add HP and extra behavior to aliens.
• Allows dynamic addition of features without modifying the original Alien class.

Flyweight

• Introduced AlienType and AlienTypeFactory to share intrinsic alien data (appearance, base stats).
• Reduces memory usage significantly when rendering many aliens.

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3. Behavioral Design Patterns

Observer

• Implemented a game Status Bar showing:
  • Score
  • Aliens defeated
  • Remaining time
• Status bar visually responds to events (low time, win, game over).

State

• Refactored the game phases into separate states:
  • Main Menu
  • Level 1
  • Level 2
  • Game Won
  • Game Over
• Each state encapsulates its own behavior → easier to add new levels.

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🗂 Repository Structure

/src /game

• Board.java
• SpaceInvaders.java
• SpriteManager.java // Singleton
• GameState classes // State Pattern
• Observer interfaces // Observer Pattern
• Factory classes // Factory Method
• AlienDecorator... // Decorator Pattern
• AlienTypeFactory... // Flyweight Pattern /report

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UML Diagrams

Detailed diagrams for all phases can be found in the project report:

• Original class diagrams
• Refactored diagrams (Creational, Structural, Behavioral)

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Team Members

• Hajar Habiburahman
• Rawan Tallha
• Rital Shilli

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University of Jeddah

College of Computer Science and Engineering
Department of Software Engineering

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📥 How to Run

1. Clone the repository:

   git clone https://github.com/RitalShilli3/java-space-invaders