Multithreaded Ferry Simulation

A Java-based Operating Systems project that simulates a ferry transporting vehicles between two sides of a city. The project focuses on thread synchronization, mutual exclusion, FIFO queue handling, deadlock avoidance, and basic runtime statistics.

Overview

The simulation contains:

• 12 cars, 10 minibuses, and 8 trucks
• one ferry travelling between Side A and Side B
• two toll booths on each side
• FIFO waiting queues on both sides
• ferry capacity control with 20 total capacity units
• random delays for tolls, boarding, travelling, unloading, and return waiting
• detailed event logging
• final statistics such as average waiting time, maximum waiting time, trip count, and ferry utilization ratio

Synchronization Concepts

The implementation uses standard Java concurrency primitives:

• Thread for vehicles and the ferry
• Semaphore for toll booth access
• ReentrantLock for shared ferry and queue state
• Condition for waiting and signaling state changes

Busy waiting is not used. Vehicles wait through proper synchronization mechanisms until the ferry is ready, their queue order is valid, and boarding/unloading rules are satisfied.

Project Structure

src/
├── Ferry.java              # Ferry thread logic
├── FerrySimulation.java    # Main entry point
├── Side.java               # Side A / Side B enum
├── Simulation.java         # Shared state, synchronization, logging, statistics
└── Vehicle.java            # Vehicle thread logic

sample-output.txt           # Example execution log
run.ps1                     # Windows PowerShell run script
run.sh                      # Linux/macOS run script

Requirements

• Java 17 or newer

How to Run

Windows PowerShell

mkdir out
javac -encoding UTF-8 -d out src\*.java
java -cp out FerrySimulation

or:

.\run.ps1

Linux / macOS

mkdir -p out
javac -encoding UTF-8 -d out src/*.java
java -cp out FerrySimulation

or:

chmod +x run.sh
./run.sh

Example Output

The program prints timestamped events such as:

[Time 126] CAR-11 joined queue on Side B (queue length = 1)
[Time 179] Ferry loaded CAR-11 (current load = 1/20)
[Time 575] Ferry departed from Side B to Side A (load = 19, waitingA = 12, waitingB = 3)
[Time 9698] CAR-2 completed round trip (completed = 30/30)

At the end, it also prints statistics:

Vehicles completed: 30/30
Average waiting time per vehicle: ... ms
Average waiting time per boarding: ... ms
Maximum waiting time: ... ms
Number of ferry trips: ...
Ferry utilization ratio: ...

Main Rules Implemented

• Vehicles must pass through a toll booth before joining a queue.
• Each side has two toll booths.
• Vehicles are loaded according to FIFO order.
• The ferry capacity cannot exceed 20 units.
• Only one vehicle can board at a time.
• Boarding is not allowed while the ferry is travelling or unloading.
• The ferry departs when it is full, no additional FIFO-valid vehicle can fit, the waiting threshold is reached, or the opposite side needs service.
• The simulation ends when all vehicles complete their full round trip.

Notes

This is a small concurrency simulation intended for Operating Systems coursework and Java threading practice.