Java Code Reading Examples
Pong Game - Complete Java Project

Pong Game - Complete Java Project

Java Pong Game Project

This is a complete Java desktop application that implements the classic Pong game using Java Swing and AWT. This project demonstrates object-oriented programming principles, game loops, event handling, and graphics programming in Java.

Learning Objectives: This project covers GUI programming, inheritance, polymorphism, event handling, threading, and game development concepts in Java.

🎮 Game Overview

Pong is a classic arcade game featuring two paddles and a bouncing ball. Players control paddles to prevent the ball from reaching their side of the screen while trying to score points against their opponent.

Game Features

  • Two-player gameplay with keyboard controls
  • Dynamic ball physics with increasing difficulty
  • Real-time scoring system
  • Collision detection for paddles and boundaries
  • Smooth animation using game loop threading

Controls

  • Player 1 (Blue Paddle): W (up) and S (down)
  • Player 2 (Red Paddle): ↑ (up) and ↓ (down)

📁 Project Structure

This project follows a clean object-oriented design with separate classes for each game component:

PongGame/
├── PongGame.java      # Main entry point
├── GameFrame.java     # Window/frame setup
├── GamePanel.java     # Game logic and rendering
├── Ball.java          # Ball object and physics
├── Paddle.java        # Paddle objects and controls
├── Score.java         # Score display and tracking
└── README.md          # Project documentation

🔍 Architecture Analysis

Design Patterns Used

  1. Component-Based Architecture: Each game element (Ball, Paddle, Score) is a separate class
  2. Inheritance: Game objects extend Rectangle for built-in collision detection
  3. Runnable Interface: GamePanel implements Runnable for threading
  4. Event Handling: Custom KeyAdapter for input processing

Key Programming Concepts

Object-Oriented Programming
  • Inheritance: Ball, Paddle, and Score extend Rectangle
  • Encapsulation: Private fields with public methods
  • Polymorphism: Different draw() implementations for each object
  • Composition: GamePanel contains multiple game objects
Game Programming Fundamentals
  • Game Loop: Continuous update-render cycle in GamePanel.run()
  • Delta Time: Frame-rate independent timing
  • Collision Detection: Using Rectangle intersection methods
  • State Management: Tracking game state and object positions
Java Swing/AWT Graphics
  • Custom Painting: Override paint() method for rendering
  • Double Buffering: Off-screen image creation for smooth animation
  • Graphics Context: Using Graphics object for drawing operations
  • Event Handling: KeyListener for user input

📚 Source Code Files

Click on any file below to view the complete source code with detailed explanations:

Core Game Files

📄 PongGame.java - Main Entry Point The main class that starts the game by creating a GameFrame

🖼️ GameFrame.java - Window Setup
JFrame setup with window properties and game panel integration

🎮 GamePanel.java - Game Engine Core game logic, rendering, collision detection, and game loop

Game Objects

⚽ Ball.java - Ball Physics Ball movement, collision response, and rendering

🏓 Paddle.java - Player Controls Paddle movement, input handling, and drawing

🏆 Score.java - Score Display Score tracking and on-screen display

🔧 How to Run

  1. Setup: Copy all Java files to a new directory
  2. Compile: javac *.java
  3. Run: java PongGame
  4. Play: Use W/S for left paddle, ↑/↓ for right paddle
Maven Setup: For a Maven project, place source files in src/main/java/ and ensure your main class path is configured correctly.

🎯 Learning Focus Areas

When studying this code, pay attention to:

1. Game Loop Architecture (GamePanel.run())

  • How the continuous loop handles timing
  • The relationship between move(), checkCollision(), and repaint()
  • Frame rate control using delta time

2. Collision Detection (GamePanel.checkCollision())

  • Ball-paddle intersection using Rectangle.intersects()
  • Boundary collision detection
  • Physics response (velocity changes)

3. Event-Driven Programming (Paddle.keyPressed()/keyReleased())

  • How keyboard input translates to game actions
  • State management for continuous movement
  • Player differentiation using ID system

4. Graphics Programming (All draw() methods)

  • Custom rendering with Graphics2D
  • Color management and drawing primitives
  • Double buffering for smooth animation

🚀 Enhancement Ideas

Consider these improvements to deepen your understanding:

Beginner Enhancements
  • Add sound effects for ball hits and scoring
  • Implement a pause/resume feature
  • Add a main menu screen
  • Create different ball colors or sizes
Intermediate Enhancements
  • Add AI for single-player mode
  • Implement power-ups or special effects
  • Add difficulty levels with varying ball speeds
  • Create a tournament mode with multiple rounds
Advanced Enhancements
  • Refactor using design patterns (Strategy, Observer)
  • Add network multiplayer support
  • Implement smooth interpolation for movement
  • Add particle effects for ball collisions

🐛 Code Analysis Questions

As you read through the code, consider these questions:

  1. Bug Alert: Can you spot the bug in Ball.java line 27? What should it be?
  2. Performance: How could the collision detection be optimized?
  3. Design: What if you wanted to add a third paddle? How would the design need to change?
  4. Threading: Why is the game loop run in a separate thread?

📖 Related Concepts

This project demonstrates many fundamental programming concepts:

💡 Study Tip: Start by running the game, then trace through the code from PongGame.main() to understand the flow. Focus on one component at a time before understanding how they interact.