# Eighth Assignment: Multithreading Basics

## Table of contents
- [Introduction](#introduction)
- [Objectives 🎯](#objectives-)
- [Theoretical Questions 📝](#theoretical-questions-)
- [Practical Questions 💻](#practical-questions-)
- [Evaluation ⚖️](#evaluation-)
- [Submission ⌛](#submission-)
- [Additional Resources 📚](#additional-resources-)

## Important Note:
This project is configured as a **Maven project**. If you're opening this project in an IDE (like IntelliJ IDEA or VS Code), please ensure you import it as a Maven project so that dependencies and build settings are recognized automatically.

To run the project from the command line, use:
```bash
mvn compile
mvn exec:java -Dexec.mainClass="Main"
```

## Introduction
Welcome to your Eighth Advanced Programming (AP) Assignment. This project is divided into two main sections:

1. **Theoretical Questions**: Analyze key multithreading concepts (Start vs Run, Daemon threads, and Lambdas).
2. **Practical Questions**: Implement a **Simulated Download Manager**. You will use Java Threads to simulate downloading a file in multiple chunks concurrently.

> **⚠️ Note:** This is a **local simulation only**. There is no actual network activity, URL connection, or socket programming involved. The goal is to practice thread management and state observation.

## Objectives 🎯

By completing this assignment, you will:
- Apply **multithreading** basics using the `Thread` class and `Runnable` interface.
- Understand how to manage multiple worker threads performing independent tasks.
- Implement a monitor thread to observe the progress of other threads.
- Practice using `start()` and `join()` for thread lifecycle management.

## Theoretical Questions 📝
**Note: Please answer these questions in a Markdown file (Report.md) and place it in the root directory of your fork. Include code or screenshots where you see fit.**

### 1. `start()` vs `run()`

```java  
public class StartVsRun {    
    static class MyRunnable implements Runnable {    
        public void run() {    
            System.out.println("Running in: " + Thread.currentThread().getName()); 
        }    
    }    
    public static void main(String[] args) throws InterruptedException {    
        Thread t1 = new Thread(new MyRunnable(), "Thread-1");    
        System.out.println("Calling run()");    
        t1.run();    
        Thread.sleep(100);    
    
        Thread t2 = new Thread(new MyRunnable(), "Thread-2");    
        System.out.println("Calling start()");    
        t2.start();    
    }  
}  
```  

**Questions:**

- What output do you get from the program? Why?

- What’s the difference in behavior between calling `start()` and `run()`?

---  

### 2. Daemon Threads

```java  
public class DaemonExample {    
    static class DaemonRunnable implements Runnable {    
        public void run() {    
            for(int i = 0; i < 20; i++) {    
                System.out.println("Daemon thread running...");    
                try {    
                    Thread.sleep(500);    
                } catch (InterruptedException e) {    
                 //[Handling Exception...]  
                }            
            }    
        }    
    }    
    public static void main(String[] args) {    
        Thread thread = new Thread(new DaemonRunnable());    
        thread.setDaemon(true);    
        thread.start();    
        System.out.println("Main thread ends.");    
    }  
}  
```  

**Questions:**
- What output do you get from the program? Why?

- What happens if you remove `thread.setDaemon(true)`?

- What are some real-life use cases of daemon threads?

  
---  

### 3. A shorter way to create threads

```java  
public class ThreadDemo {  
    public static void main(String[] args) {  
        Thread thread = new Thread(() -> {  
            System.out.println("Thread is running using a ...!");  
        });  
  
        thread.start();  
    }  
}   
```  

**Questions:**
- What output do you get from the program?

- What is the `() -> { ... }` syntax called?

- How is this code different from creating a class that extends `Thread` or implements `Runnable`?


## Practical Questions 💻

### Simulated Download Manager
You are tasked with completing a skeleton project for a download manager. The application reads a configuration file, splits a "file" into several chunks, and assigns each chunk to a dedicated worker thread.

#### 🏗 Project Structure
- `src/main/resources/download_config.txt`: Contains simulation parameters (file size, chunk count, delays).
- `DownloadWorker.java`: The logic for simulating a chunk download (needs implementation).
- `ProgressMonitor.java`: A thread that periodically prints the total progress (needs implementation).
- `Main.java`: The entry point that initializes chunks, starts threads, and waits for completion.
- `ChunkStatus.java`: Data class holding the state of individual chunks.

#### 🛠 What You Need to Do
In the provided source code, look for **`// TODO`** comments. You must:

1.  **Implement `DownloadWorker`**:
    - Record start/end times for each chunk.
    - Use a loop to simulate progress based on the random delays and step sizes provided in the config.
    - Update the shared `ChunkStatus` object so the monitor can see progress.
2.  **Implement `ProgressMonitor`**:
    - Periodically calculate the total downloaded megabytes across all chunks.
    - Exit gracefully once all chunks are marked as completed.
3.  **Complete `Main`**:
    - Properly instantiate and `start()` the worker threads and the monitor thread.
    - Use `join()` to ensure the main thread waits for all workers to finish before printing the final report.

#### ⚙️ Configuration
The simulation behavior is controlled by `src/main/resources/download_config.txt`. You can modify these values to test different scenarios (e.g., more chunks or faster/slower speeds).

---

## Evaluation ⚖️

Your work will be evaluated based on:

- **Thread Management**: Correct use of `start()` and `join()`.
- **Simulation Logic**: Correct implementation of the loops and random delays in the worker threads.
- **Thread Safety**: Following the constraint of each worker only writing to its own assigned object.
- **Code Quality**: Readable code and proper use of Java conventions.

**Total: 500 points**
- 🧠 Theoretical Questions – 150 points
- 💻 Practical Task (Download Manager) – 350 points

## Submission ⌛

1. Add your mentor as a contributor to the project.
2. Create a `develop` branch for implementing features.
3. Use Git for regular code commits.
4. Push your code and the answers file (Report.md) to the remote repository.
5. Submit a pull request to merge the `develop` branch with `main`.

**Deadline:** **Friday, June 5** (15th of Khordad)

## Additional Resources 📚

- [Java Concurrency and Multithreading](https://jenkov.com/tutorials/java-concurrency/index.html)
- [Creating and Starting Java Threads](https://jenkov.com/tutorials/java-concurrency/creating-and-starting-threads.html)
- [Thread.join() explained](https://docs.oracle.com/javase/8/docs/api/java/lang/Thread.html#join--)