Collision Avoidance System

A real-time concurrent simulation in Java where each car operates on an independent thread, simulating high-concurrency environments with parallel execution. Red and blue cars share a single-lane bridge; a TrafficController monitor serializes access to prevent race conditions and collisions.

Multithreading · Thread Synchronization · Swing · Monitor Pattern

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Highlights

• Monitor-based synchronization — A TrafficController acts as a monitor using synchronized, wait(), and notifyAll() to serialize access to the shared bridge. Cars from one direction wait while the opposite direction is crossing; when the bridge clears, waiting threads are woken.
• Concurrent car actors — Each car runs as a Runnable on its own thread. Hundreds of car threads can run in parallel while the controller enforces mutual exclusion at the bridge.
• EDT-safe UI — Long-running car logic runs off the Swing Event Dispatch Thread. SwingUtilities.invokeLater is used when mutating UI state (e.g. adding cars), and a dedicated repaint thread keeps the GUI responsive without blocking the EDT.
• Deadlock avoidance — Clear enter/leave protocols and single-monitor design ensure the system remains collision-free and avoids deadlock even under heavy concurrent load.

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How to Run

Requirements: Java JDK (e.g. 8+)

cd Collision_Avoidance_System
javac *.java
java Main

Use Add Left and Add Right to spawn red and blue cars. They cross the bridge concurrently; the TrafficController ensures no collisions.

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Project Structure

File	Role
Main.java	Entry point; launches UI and background repaint thread
CarWindow.java	Swing frame with Add Left / Add Right buttons
CarWorld.java	Panel that spawns car threads, shares TrafficController, uses invokeLater for UI updates
Car.java	Car actor (Runnable); calls controller enter/leave around bridge segment
TrafficController.java	Monitor: enterLeft/enterRight, leaveLeft/leaveRight; wait/notifyAll for coordination
image/	Assets: redcar.gif, bluecar.gif, bridge1.gif