Mine Pump System - True Object-Oriented Design

Overview

This project is a Java implementation of the Mine Pump system, following the Real Object-Oriented (OO) approach described by Carlo Pescio. Instead of using a centralized controller, the design distributes responsibilities across collaborating objects, allowing for better modularity, testability, and maintainability.

Problem Description

The Mine Pump system is responsible for managing water levels in a mine while ensuring safety from gas hazards. The system consists of:

• Water Level Sensors: Determines when to pump water out of the sump.
• Gas Sensors: Monitors carbon monoxide, methane, and airflow.
• Pump: Removes water when necessary but cannot operate under unsafe conditions.
• Siren: Triggers warnings when gas levels become critical or the pump fails.

The challenge is to implement this system without a monolithic controller, ensuring that each object encapsulates its own behavior.

Implementation

The project is structured into several key classes:

• BasicSumpProbe – Determines when pumping is required.
• GasSensor – Evaluates gas safety levels.
• SafeEngine – Ensures the pump operates only when conditions are safe.
• GasAlarm – Triggers alerts when hazardous conditions arise.
• SumpPump – Manages the actual pumping process.
• MinePlant – Acts as a factory/builder to configure and instantiate the system.

Class Diagram

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Running the Project

To run the project, compile the Java files and execute the main entry point. Since this implementation focuses on a true OO design, it can be easily extended to integrate with actual hardware or simulations.

References

• Carlo Pescio’s article on Life without a Controller: Original Post

What does true object-oriented means?

This application follows these four fundamental principles:

• No null (why?)
• No code in constructors (why?)
• No getters and setters (why?)
• No mutable objects (why?)
• No static methods, not even private ones (why?)
• No instanceof, type casting, or reflection (why?)
• No implementation inheritance (why?)
• No public methods without @Override
• No statements in test methods except assertThat (why?)

If you want to know more about true object-oriented programming, I recommend these books:

• Elegant Objects (Volume 1) by Yegor Bugayenko
• Elegant Objects (Volume 2) by Yegor Bugayenko
• Object Thinking by David West