Merge PR '8th Home Work, Practical and Theoretical Questions' (#1) from develop into main

Full Mark + Bonus - Late Submission

Theoretical Questions.tex

@@ -0,0 +1,354 @@
+\documentclass[12pt,a4paper]{article}
+
+\usepackage[utf8]{inputenc}
+\usepackage[T1]{fontenc}
+\usepackage[margin=2.5cm]{geometry}
+\usepackage{listings}
+\usepackage{xcolor}
+\usepackage{hyperref}
+\usepackage{parskip}
+\usepackage{booktabs}
+\usepackage{array}
+\usepackage{titlesec}
+\usepackage{fancyhdr}
+\usepackage{amsmath}
+\usepackage{enumitem}
+
+% ── Page style ──────────────────────────────────────────────────────────────
+\pagestyle{fancy}
+\fancyhf{}
+\rhead{Advanced Programming – Assignment 8}
+\lhead{Faraz Ardeh}
+\cfoot{\thepage}
+
+% ── Section formatting ───────────────────────────────────────────────────────
+\titleformat{\section}{\large\bfseries}{Question \thesection.}{0.6em}{}
+\titleformat{\subsection}{\normalsize\bfseries}{}{0em}{}
+
+% ── Java code style ─────────────────────────────────────────────────────────
+\definecolor{javakw}{rgb}{0.13,0.13,0.60}
+\definecolor{javastr}{rgb}{0.63,0.13,0.13}
+\definecolor{javacmt}{rgb}{0.38,0.38,0.38}
+\definecolor{codebg}{rgb}{0.97,0.97,0.97}
+\definecolor{codefr}{rgb}{0.82,0.82,0.82}
+
+\lstdefinestyle{java}{
+    language=Java,
+    basicstyle=\ttfamily\small,
+    keywordstyle=\color{javakw}\bfseries,
+    stringstyle=\color{javastr},
+    commentstyle=\color{javacmt}\itshape,
+    numberstyle=\tiny\color{gray},
+    numbers=left,
+    stepnumber=1,
+    numbersep=8pt,
+    backgroundcolor=\color{codebg},
+    frame=single,
+    rulecolor=\color{codefr},
+    breaklines=true,
+    breakatwhitespace=false,
+    showstringspaces=false,
+    tabsize=4,
+    captionpos=b,
+}
+
+\lstset{style=java}
+
+% ── Inline code ─────────────────────────────────────────────────────────────
+\newcommand{\code}[1]{\texttt{\small #1}}
+
+% ────────────────────────────────────────────────────────────────────────────
+\begin{document}
+
+% ── Title page ───────────────────────────────────────────────────────────────
+\begin{titlepage}
+    \centering
+    \vspace*{3cm}
+    {\Huge\bfseries Multithreading Basics\par}
+    \vspace{0.8cm}
+    {\large Assignment 8 – Theoretical Questions\par}
+    \vspace{0.4cm}
+    {\large Advanced Programming (AP)\par}
+    \vspace{2cm}
+    \rule{0.6\linewidth}{0.5pt}\\[0.4cm]
+    {\large\bfseries Faraz Ardeh\par}
+    \vspace{0.3cm}
+    {\normalsize fa.ardeh@gmail.com\par}
+    \vspace{0.6cm}
+    {\normalsize Shahid Beheshti University\par}
+    \vspace{0.3cm}
+    {\normalsize June 2026\par}
+    \vfill
+\end{titlepage}
+
+\tableofcontents
+\newpage
+
+% ════════════════════════════════════════════════════════════════════════════
+\section{\code{start()} vs \code{run()}}
+% ════════════════════════════════════════════════════════════════════════════
+
+The program under analysis:
+
+\begin{lstlisting}[caption={StartVsRun.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();
+    }
+}
+\end{lstlisting}
+
+\subsection{Expected output}
+
+\begin{lstlisting}[language={},numbers=none,backgroundcolor=\color{codebg}]
+Calling run()
+Running in: main
+Calling start()
+Running in: Thread-2
+\end{lstlisting}
+
+\subsection{Why this output?}
+
+\textbf{The \code{t1.run()} call:}
+Calling \code{run()} on a \code{Thread} object is just an ordinary method call, exactly
+like calling any other method on any other object.
+No new OS thread is created or scheduled.
+The body of \code{run()} executes \emph{synchronously} inside the calling thread,
+which is \code{main}.
+Therefore \code{Thread.currentThread().getName()} returns \texttt{"main"},
+not \texttt{"Thread-1"}.
+The thread object \texttt{t1} was constructed but its native thread was never started.
+
+\textbf{The \code{t2.start()} call:}
+\code{start()} allocates a new OS-level thread, registers it with the JVM scheduler,
+and returns to the caller \emph{immediately} (it does not wait for \code{run()} to finish).
+The new thread then invokes \code{run()} autonomously and concurrently.
+Inside that new thread, \code{Thread.currentThread().getName()} correctly
+returns \texttt{"Thread-2"}.
+
+\subsection{Key differences at a glance}
+
+\begin{center}
+\begin{tabular}{>{\bfseries}lll}
+\toprule
+Aspect & \code{run()} & \code{start()} \\
+\midrule
+New thread created?   & No  & Yes (exactly one) \\
+Execution thread      & Current thread & New thread \\
+Blocking behaviour    & Synchronous (caller waits) & Asynchronous (returns at once) \\
+Can be called twice?  & Yes, legal & No – throws \code{IllegalThreadStateException} \\
+Useful for?           & Testing \code{run()} logic directly & True concurrent execution \\
+\bottomrule
+\end{tabular}
+\end{center}
+
+\textbf{Summary:}
+\code{run()} is simply a method call; \code{start()} is what actually creates and
+launches a new thread of execution. Calling \code{run()} instead of \code{start()} is
+one of the most common multithreading bugs in Java – the code compiles and
+"works", but no concurrency ever happens.
+
+% ════════════════════════════════════════════════════════════════════════════
+\section{Daemon Threads}
+% ════════════════════════════════════════════════════════════════════════════
+
+\begin{lstlisting}[caption={DaemonExample.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.");
+    }
+}
+\end{lstlisting}
+
+\subsection{Expected output (with \code{setDaemon(true)})}
+
+\begin{lstlisting}[language={},numbers=none,backgroundcolor=\color{codebg}]
+Main thread ends.
+Daemon thread running...
+(program terminates -- usually 0-2 more lines, non-deterministic)
+\end{lstlisting}
+
+\textbf{Why?}
+The JVM shuts down when there are no \emph{non-daemon} threads still alive.
+After \code{main()} prints \texttt{"Main thread ends."} and returns, the only surviving
+thread is the daemon thread.
+Because it is marked as a daemon, the JVM does \emph{not} wait for it to
+finish – it exits immediately (or after one scheduling quantum), abruptly
+terminating the daemon thread.
+The daemon may manage to print zero, one, or a few lines before termination,
+depending entirely on OS thread scheduling; this is non-deterministic.
+
+\subsection{What happens if you remove \code{thread.setDaemon(true)}?}
+
+Without that call the thread becomes a regular \emph{user thread} (the default).
+The JVM rule is: \textbf{wait for all user threads to finish before exiting.}
+The daemon thread (now a user thread) will sleep 500 ms per iteration and
+loop 20 times – the program will take approximately $20 \times 0.5 = 10$ seconds
+to terminate, and all 20 lines of \texttt{"Daemon thread running..."} will be
+printed in full before the JVM exits.
+
+\subsection{Real-life use cases of daemon threads}
+
+Daemon threads are ideal for background housekeeping work that should not
+prevent the application from exiting cleanly.
+
+\begin{enumerate}[leftmargin=2em]
+    \item \textbf{Garbage Collection.}
+          The JVM's garbage collector runs as a daemon thread;
+          it must not keep the JVM alive on its own.
+
+    \item \textbf{Log flushing.}
+          A background thread that periodically flushes buffered log entries
+          to disk. If the application finishes, unsaved logs are
+          an acceptable loss compared with hanging the process.
+
+    \item \textbf{Cache invalidation / expiry.}
+          A thread that sweeps an in-memory cache and removes stale entries
+          does not need to outlive the application.
+
+    \item \textbf{Heartbeat / health-check threads.}
+          Service-mesh sidecars and microservices often send periodic
+          pings to a service-discovery system.
+          These should die with the service, not keep it alive.
+
+    \item \textbf{IDE background indexing.}
+          IntelliJ IDEA's indexer and VS Code's language-server workers
+          are typically daemon-like: if you close the IDE, you do not
+          want to wait for them to finish indexing.
+\end{enumerate}
+
+% ════════════════════════════════════════════════════════════════════════════
+\section{A Shorter Way to Create Threads – Lambda Expressions}
+% ════════════════════════════════════════════════════════════════════════════
+
+\begin{lstlisting}[caption={ThreadDemo.java}]
+public class ThreadDemo {
+    public static void main(String[] args) {
+        Thread thread = new Thread(() -> {
+            System.out.println("Thread is running using a lambda!");
+        });
+
+        thread.start();
+    }
+}
+\end{lstlisting}
+
+\subsection{Expected output}
+
+\begin{lstlisting}[language={},numbers=none,backgroundcolor=\color{codebg}]
+Thread is running using a lambda!
+\end{lstlisting}
+
+\subsection{What is \code{() -> \{ \ldots \}} called?}
+
+The \code{() -> \{ \ldots \}} syntax is called a \textbf{lambda expression}
+(also known as an \emph{anonymous function} or \emph{arrow function} in
+other languages).
+
+A lambda expression is a concise way to provide an implementation of a
+\emph{functional interface} – any interface that declares exactly one abstract
+method.
+\code{Runnable} is a functional interface: its single abstract method is
+\code{void run()}.
+The lambda \code{() -> \{ \ldots \}} supplies that implementation inline,
+without naming it.
+
+\subsection{How does this differ from other approaches?}
+
+There are three common ways to supply a \code{Runnable} to a \code{Thread}:
+
+\begin{lstlisting}[caption={Three equivalent approaches}]
+// 1. Class that extends Thread
+class MyThread extends Thread {
+    public void run() { System.out.println("extends Thread"); }
+}
+new MyThread().start();
+
+// 2. Named class that implements Runnable
+class MyRunnable implements Runnable {
+    public void run() { System.out.println("implements Runnable"); }
+}
+new Thread(new MyRunnable()).start();
+
+// 3. Lambda expression (shortest)
+new Thread(() -> System.out.println("lambda")).start();
+\end{lstlisting}
+
+\begin{center}
+\begin{tabular}{>{\bfseries}lllll}
+\toprule
+Approach & Boilerplate & Separate class? & Captures outer vars? & Extensible? \\
+\midrule
+\code{extends Thread}   & High   & Yes (named) & No                & Inherits Thread \\
+\code{implements Runnable} & Medium & Yes (named) & No             & Yes \\
+Anonymous class         & Medium & Yes (anon.) & Yes (eff.\ final) & Yes \\
+Lambda                  & \textbf{Minimal} & No & Yes (eff.\ final) & No \\
+\bottomrule
+\end{tabular}
+\end{center}
+
+\textbf{Key advantages of lambdas:}
+\begin{itemize}[leftmargin=2em]
+    \item \textbf{Conciseness.}
+          No need to declare a class, override a method, or write a constructor.
+          A single line can create and start a thread.
+
+    \item \textbf{Readability.}
+          The intent (``run this block of code in a new thread'') is immediately
+          obvious to the reader.
+
+    \item \textbf{Variable capture.}
+          A lambda can reference local variables from the enclosing scope as long
+          as they are effectively final (i.e., never reassigned after declaration).
+          This is often more convenient than passing data through a constructor.
+
+    \item \textbf{Functional programming patterns.}
+          Lambdas work seamlessly with the Java Streams API, \code{CompletableFuture},
+          \code{ExecutorService}, and other modern concurrency utilities that accept
+          \code{Runnable} or \code{Callable} arguments.
+\end{itemize}
+
+\textbf{Limitation:}
+Because a lambda is not a subclass of \code{Thread}, it cannot override thread
+life-cycle methods such as \code{interrupt()} or \code{setUncaughtExceptionHandler()}
+directly inside the lambda body.
+When that level of control is needed, a named class is more appropriate.
+
+% ── Footer note ──────────────────────────────────────────────────────────────
+\vfill
+\begin{center}
+    \small\color{gray}
+    Advanced Programming – Assignment 8 \quad|\quad
+    Faraz Ardeh \quad|\quad
+    Shahid Beheshti University \quad|\quad
+    June 2026
+\end{center}
+
+\end{document}

src/main/java/DownloadWorker.java

@@ -2,10 +2,7 @@ import java.util.Random;
 
 /**
  * Simulates downloading a single chunk of a file.
- *
- * <p>This class is intentionally provided as a skeleton for students.
- * The main multithreading and simulation logic should be completed
- * in the run() method.</p>
+ * Each worker writes only to its own assigned ChunkStatus object.
  */
 public class DownloadWorker implements Runnable {
 
@@ -21,23 +18,33 @@ public class DownloadWorker implements Runnable {
 
     @Override
     public void run() {
-        // TODO: Record the chunk start time in chunkStatus.
-        double downloaded = 0.0;
+        // Record the start time for this chunk
+        chunkStatus.setStartTimeMs(System.currentTimeMillis());
 
-        // TODO: Print a message that this chunk has started downloading.
+        double downloaded = 0.0;
+        int delayRange = config.getMaxStepDelayMs() - config.getMinStepDelayMs();
+        double stepRange = config.getMaxStepDownloadMB() - config.getMinStepDownloadMB();
 
         while (downloaded < chunkStatus.getChunkSizeMB()) {
-            // TODO: Generate a random sleep delay between min and max delay.
-            // TODO: Sleep for that delay.
-            // TODO: Generate a random download amount for this step.
-            // TODO: Increase downloaded, but do not go beyond chunk size.
-            // TODO: Save the updated downloaded value into chunkStatus.
-            // TODO: Optionally print step-by-step progress.
+            // Random delay simulating network latency for this step
+            int delay = config.getMinStepDelayMs() + (delayRange > 0 ? random.nextInt(delayRange) : 0);
+            try {
+                Thread.sleep(delay);
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                return;
+            }
+
+            // Random amount downloaded in this step, capped at remaining size
+            double step = config.getMinStepDownloadMB() + random.nextDouble() * stepRange;
+            downloaded = Math.min(downloaded + step, chunkStatus.getChunkSizeMB());
+
+            // Write only to this worker's own ChunkStatus (thread-safe by design)
+            chunkStatus.setDownloadedMB(downloaded);
         }
 
-        // TODO: Mark the chunk as completed.
-        // TODO: Record the chunk end time in chunkStatus.
-        // TODO: Print a message that this chunk has finished downloading.
+        // Mark completion and record end time
+        chunkStatus.setEndTimeMs(System.currentTimeMillis());
+        chunkStatus.setCompleted(true);
     }
-
 }

src/main/java/Main.java

@@ -3,7 +3,7 @@ import java.util.List;
 
 public class Main {
     public static void main(String[] args) {
-        System.out.println("=== Simulated Download Manager ===");
+        System.out.println("=== Simulated Download Manager ===\n");
 
         // 1. Read config
         DownloadConfig config;
@@ -14,94 +14,98 @@ public class Main {
             return;
         }
 
-        System.out.println("File name: " + config.getFileName());
-        System.out.println("Total size (MB): " + config.getTotalSizeMB());
-        System.out.println("Chunk count: " + config.getChunkCount());
+        System.out.println("File name   : " + config.getFileName());
+        System.out.println("Total size  : " + config.getTotalSizeMB() + " MB");
+        System.out.println("Chunks      : " + config.getChunkCount());
+        System.out.println("Step delay  : " + config.getMinStepDelayMs()
+                + "–" + config.getMaxStepDelayMs() + " ms");
+        System.out.println("Step size   : " + config.getMinStepDownloadMB()
+                + "–" + config.getMaxStepDownloadMB() + " MB");
         System.out.println();
 
-        // 2. Create chunks
+        // ── MULTITHREADED RUN ──────────────────────────────────────────────
+
+        System.out.println("━━━ Multithreaded Download ━━━");
+
+        // 2. Create chunk status objects
         List<ChunkStatus> chunks = ChunkUtils.createChunks(
-                config.getTotalSizeMB(),
-                config.getChunkCount()
-        );
+                config.getTotalSizeMB(), config.getChunkCount());
 
-        // 3. Create worker threads
+        // 3. Create one worker thread per chunk
         List<Thread> workerThreads = new ArrayList<>();
-
         for (ChunkStatus chunk : chunks) {
             DownloadWorker worker = new DownloadWorker(chunk, config);
-            Thread workerThread = new Thread(worker, "Worker-" + chunk.getChunkId());
-
-            workerThreads.add(workerThread);
-
-            // TODO:
-            // Students may print helpful debug information here,
-            // for example which chunk is assigned to which worker thread.
+            Thread t = new Thread(worker, "Worker-" + chunk.getChunkId());
+            workerThreads.add(t);
         }
 
-        // 4. Create and start monitor thread
+        // 4. Create and start the monitor thread before workers so it is
+        //    already polling when the first worker begins
         ProgressMonitor monitor = new ProgressMonitor(config, chunks);
         Thread monitorThread = new Thread(monitor, "Progress-Monitor");
+        monitorThread.start();
 
-        // TODO:
-        // Start the monitor thread before starting the workers
-        // so that progress can be displayed while downloading happens.
-        //
-        // Example idea:
-        // monitorThread.start();
+        // 5. Start all worker threads
+        long multiStart = System.currentTimeMillis();
+        for (Thread t : workerThreads) {
+            t.start();
+        }
 
-        // 5. Start worker threads
-        // TODO:
-        // Start each worker thread in workerThreads.
-        // Use a loop and call start() on each thread.
-
-        // 6. Wait for workers to finish
-        // TODO:
-        // Wait for all worker threads to complete by calling join().
-        // This should be done inside a try-catch block for InterruptedException.
-        //
-        // Hint:
-        // for (Thread thread : workerThreads) {
-        //     thread.join();
-        // }
-
-        // TODO:
-        // After all workers finish, the monitor thread may also need to stop.
-        // Depending on how ProgressMonitor is implemented, students may:
-        // - wait for it to finish on its own, or
-        // - add a stopping mechanism in ProgressMonitor later.
-        //
-        // If your monitor finishes automatically, you may join it here.
-
-        // NOTE:
-        // this final report may show 0 progress because no worker has actually run yet.
-        // Until students complete the thread start/join TODOs above,
+        // 6. Wait for every worker to finish before printing the final report
+        try {
+            for (Thread t : workerThreads) {
+                t.join();
+            }
+            // Monitor exits on its own once it detects all chunks are done;
+            // join here to make sure the final "All chunks completed" line is printed
+            monitorThread.join();
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            System.out.println("Main thread interrupted while waiting for workers.");
+            return;
+        }
+        long multiTime = System.currentTimeMillis() - multiStart;
 
         // 7. Print final report
         System.out.println();
-        System.out.println("=== Final Report ===");
-
-        int completedChunks = 0;
-        double downloadedMB = 0.0;
-
+        System.out.println("━━━ Final Report ━━━");
+        int completedCount = 0;
+        double totalDownloaded = 0.0;
         for (ChunkStatus chunk : chunks) {
-            downloadedMB += chunk.getDownloadedMB();
-
-            if (chunk.isCompleted()) {
-                completedChunks++;
-            }
-
-            System.out.println(
-                    "Chunk " + chunk.getChunkId()
-                            + ": " + chunk.getDownloadedMB()
-                            + "/" + chunk.getChunkSizeMB()
-                            + " MB"
-            );
+            totalDownloaded += chunk.getDownloadedMB();
+            if (chunk.isCompleted()) completedCount++;
+            System.out.printf("  Chunk #%d : %.1f / %.1f MB  (%.2fs)%n",
+                    chunk.getChunkId(),
+                    chunk.getDownloadedMB(),
+                    chunk.getChunkSizeMB(),
+                    chunk.getDownloadDurationMs() / 1000.0);
         }
+        System.out.printf("  Completed : %d / %d chunks%n", completedCount, chunks.size());
+        System.out.printf("  Downloaded: %.1f / %.1f MB%n",
+                totalDownloaded, (double) config.getTotalSizeMB());
+        System.out.printf("  Wall time : %.2f seconds%n%n", multiTime / 1000.0);
+
+        // ── SEQUENTIAL RUN (Bonus – comparison) ───────────────────────────
+
+        System.out.println("━━━ Sequential Download (Bonus Comparison) ━━━");
+        List<ChunkStatus> seqChunks = ChunkUtils.createChunks(
+                config.getTotalSizeMB(), config.getChunkCount());
+        long seqTime = SequentialDownloader.run(config, seqChunks);
+
+        // ── COMPARISON REPORT ──────────────────────────────────────────────
 
         System.out.println();
-        System.out.println("Completed chunks: " + completedChunks + "/" + chunks.size());
-        System.out.println("Downloaded total: " + downloadedMB + "/" + config.getTotalSizeMB() + " MB");
+        System.out.println("━━━ Performance Comparison ━━━");
+        System.out.printf("  Sequential    : %.2f seconds%n", seqTime   / 1000.0);
+        System.out.printf("  Multithreaded : %.2f seconds%n", multiTime / 1000.0);
+        System.out.printf("  Speedup       : %.2fx%n", (double) seqTime / Math.max(multiTime, 1));
+        System.out.println();
+        System.out.println("  Analysis:");
+        System.out.println("    In the multithreaded run each worker sleeps independently,");
+        System.out.println("    so all network-latency delays overlap in parallel.");
+        System.out.println("    The sequential run must wait for each chunk in turn,");
+        System.out.println("    making the total time roughly N × (average chunk time).");
+        System.out.println();
         System.out.println("Simulation finished.");
     }
 }

src/main/java/ProgressMonitor.java

@@ -1,5 +1,17 @@
+import java.util.ArrayDeque;
+import java.util.Deque;
 import java.util.List;
 
+/**
+ * Monitors and displays real-time download progress for all chunks.
+ *
+ * Bonus features implemented:
+ *  - Real-time in-place progress bar using ANSI escape codes
+ *  - Per-chunk progress bars with completion indicators
+ *  - Overall download speed (MB/s) calculation
+ *  - Estimated Time of Arrival (ETA) calculation
+ *  - Event log showing chunk start/finish events
+ */
 public class ProgressMonitor implements Runnable {
 
     private final String fileName;
@@ -7,57 +19,87 @@ public class ProgressMonitor implements Runnable {
     private final List<ChunkStatus> chunks;
     private final long monitorDelayMs;
 
+    // Event detection: track previous state to detect chunk start/finish
+    private final boolean[] wasStarted;
+    private final boolean[] wasCompleted;
+    private final Deque<String> eventLog = new ArrayDeque<>();
+    private static final int MAX_LOG_ENTRIES = 5;
+
+    // Speed and ETA tracking
+    private double previousTotalMB = 0.0;
+    private long previousTimeMs;
+
+    // In-place ANSI update tracking
+    private int lastPrintedLines = 0;
+
+    // ANSI escape codes
+    private static final String RESET  = "\033[0m";
+    private static final String BOLD   = "\033[1m";
+    private static final String DIM    = "\033[2m";
+    private static final String GREEN  = "\033[92m";
+    private static final String CYAN   = "\033[96m";
+    private static final String YELLOW = "\033[93m";
+    private static final String CLEAR_LINE = "\033[2K";
+
+    private static final int BAR_WIDTH = 30;
+
     public ProgressMonitor(DownloadConfig config, List<ChunkStatus> chunks) {
         this.fileName = config.getFileName();
         this.totalSizeMB = config.getTotalSizeMB();
         this.chunks = chunks;
         this.monitorDelayMs = 500;
+        this.previousTimeMs = System.currentTimeMillis();
+        this.wasStarted   = new boolean[chunks.size()];
+        this.wasCompleted = new boolean[chunks.size()];
     }
 
     @Override
     public void run() {
-        // TODO:
-        // Repeatedly check chunk progress until all chunks are completed.
-        // In each loop:
-        // 1. Read the downloaded size from every chunk
-        // 2. Add all downloaded amounts to totalDownloadedMB
-        // 3. Count completed chunks
-        // 4. Print a progress message
-        // 5. If completedChunks == chunks.size(), print a final monitor message and stop
-        // 6. Otherwise sleep for monitorDelayMs and continue
-
+        boolean firstPrint = true;
 
         while (true) {
             double totalDownloadedMB = 0.0;
             int completedChunks = 0;
 
-            for (ChunkStatus chunk : chunks) {
+            // 1. Read progress from every chunk and detect state-change events
+            for (int i = 0; i < chunks.size(); i++) {
+                ChunkStatus chunk = chunks.get(i);
                 totalDownloadedMB += chunk.getDownloadedMB();
+                if (chunk.isCompleted()) completedChunks++;
 
-                if (chunk.isCompleted()) {
-                    completedChunks++;
+                if (!wasStarted[i] && chunk.getStartTimeMs() > 0) {
+                    wasStarted[i] = true;
+                    addEvent(String.format("Chunk #%d started  (%.0f MB)",
+                            chunk.getChunkId(), chunk.getChunkSizeMB()));
+                }
+                if (!wasCompleted[i] && chunk.isCompleted()) {
+                    wasCompleted[i] = true;
+                    addEvent(String.format("Chunk #%d finished (%.2fs)",
+                            chunk.getChunkId(), chunk.getDownloadDurationMs() / 1000.0));
                 }
             }
 
-            double percent = 0.0;
-            if (totalSizeMB > 0) {
-                percent = (totalDownloadedMB * 100.0) / totalSizeMB;
+            // 2. Calculate speed and ETA
+            long now = System.currentTimeMillis();
+            double elapsed = (now - previousTimeMs) / 1000.0;
+            double speed = elapsed > 0.001 ? (totalDownloadedMB - previousTotalMB) / elapsed : 0.0;
+            double remaining = totalSizeMB - totalDownloadedMB;
+            double eta = (speed > 0.01) ? remaining / speed : -1.0;
+            previousTotalMB = totalDownloadedMB;
+            previousTimeMs = now;
+
+            // 3. Build and print the real-time dashboard
+            String dashboard = buildDashboard(totalDownloadedMB, completedChunks, speed, eta);
+            printInPlace(dashboard, firstPrint);
+            firstPrint = false;
+
+            // 5. Exit gracefully once all chunks are done
+            if (completedChunks == chunks.size()) {
+                System.out.println(BOLD + GREEN + "  All chunks completed! Download finished." + RESET);
+                break;
             }
 
-            System.out.printf(
-                    "Progress for %s: %.1f/%.1f MB (%.2f%%), completed chunks: %d/%d%n",
-                    fileName,
-                    totalDownloadedMB,
-                    (double) totalSizeMB,
-                    percent,
-                    completedChunks,
-                    chunks.size()
-            );
-
-
-            // TODO:
-            // If all chunks are completed, print a final message and exit the loop
-
+            // 6. Sleep before the next polling cycle
             try {
                 Thread.sleep(monitorDelayMs);
             } catch (InterruptedException e) {
@@ -66,4 +108,86 @@ public class ProgressMonitor implements Runnable {
             }
         }
     }
+
+    private void addEvent(String message) {
+        if (eventLog.size() >= MAX_LOG_ENTRIES) eventLog.pollFirst();
+        eventLog.addLast(message);
+    }
+
+    /**
+     * Overwrites the previous dashboard in-place using ANSI cursor-up sequences,
+     * producing a smooth real-time update instead of scrolling output.
+     */
+    private void printInPlace(String dashboard, boolean firstPrint) {
+        if (!firstPrint && lastPrintedLines > 0) {
+            // Move cursor up to the top of the previous dashboard
+            System.out.printf("\033[%dA", lastPrintedLines);
+        }
+        String[] lines = dashboard.split("\n", -1);
+        for (String line : lines) {
+            System.out.print(CLEAR_LINE + line + "\n");
+        }
+        System.out.flush();
+        lastPrintedLines = lines.length;
+    }
+
+    private String buildDashboard(double totalMB, int completedChunks, double speed, double eta) {
+        StringBuilder sb = new StringBuilder();
+        String divider = "  " + "─".repeat(54);
+
+        sb.append(BOLD).append(CYAN)
+          .append("  ┌─ Download Manager ─ ").append(fileName).append("\n")
+          .append(RESET);
+
+        // Per-chunk progress rows
+        for (ChunkStatus chunk : chunks) {
+            sb.append(chunkLine(chunk)).append("\n");
+        }
+
+        sb.append(DIM).append(divider).append(RESET).append("\n");
+
+        // Overall progress bar
+        double pct = totalSizeMB > 0 ? totalMB / totalSizeMB * 100.0 : 0.0;
+        sb.append(String.format("  " + BOLD + "Total  " + RESET + " %s %5.1f%%  %.1f / %.0f MB\n",
+                colorBar(pct, BAR_WIDTH), pct, totalMB, (double) totalSizeMB));
+
+        // Speed and ETA line
+        if (speed > 0.01) {
+            String etaStr = eta >= 0 ? String.format("%.1fs", eta) : "∞";
+            sb.append(String.format("  " + YELLOW + "Speed: %.2f MB/s" + RESET
+                    + "  ETA: %-8s  chunks: %d / %d\n",
+                    speed, etaStr, completedChunks, chunks.size()));
+        } else {
+            sb.append(String.format("  Warming up…  chunks: %d / %d\n",
+                    completedChunks, chunks.size()));
+        }
+
+        // Event log
+        if (!eventLog.isEmpty()) {
+            sb.append(DIM).append(divider).append(RESET).append("\n");
+            for (String event : eventLog) {
+                sb.append(DIM).append("  » ").append(event).append(RESET).append("\n");
+            }
+        }
+
+        // Remove trailing newline so split gives the right count
+        String result = sb.toString();
+        if (result.endsWith("\n")) result = result.substring(0, result.length() - 1);
+        return result;
+    }
+
+    private String chunkLine(ChunkStatus chunk) {
+        double pct = chunk.getProgressPercentage();
+        String tick = chunk.isCompleted() ? GREEN + "✓" + RESET : " ";
+        return String.format("  [%s] Chunk #%d %s %5.1f%%",
+                tick, chunk.getChunkId(), colorBar(pct, BAR_WIDTH), pct);
+    }
+
+    /** Renders a Unicode block-character progress bar with ANSI colour. */
+    private String colorBar(double percent, int width) {
+        int filled = (int) Math.round(percent / 100.0 * width);
+        filled = Math.max(0, Math.min(filled, width));
+        return GREEN + "█".repeat(filled) + RESET
+             + DIM   + "░".repeat(width - filled) + RESET;
+    }
 }

src/main/java/SequentialDownloader.java

@@ -0,0 +1,32 @@
+import java.util.List;
+
+/**
+ * Bonus Task – Sequential vs Multithreaded Comparison.
+ *
+ * Downloads all chunks one after another on the calling thread.
+ * This exists only for timing comparison with the multithreaded run;
+ * it demonstrates the speedup gained from parallel execution.
+ */
+public class SequentialDownloader {
+
+    private SequentialDownloader() {}
+
+    /**
+     * Runs each chunk sequentially on the current thread and returns
+     * the total elapsed time in milliseconds.
+     */
+    public static long run(DownloadConfig config, List<ChunkStatus> chunks) {
+        long start = System.currentTimeMillis();
+
+        for (ChunkStatus chunk : chunks) {
+            System.out.printf("[Sequential] Chunk #%d starting (%.0f MB)%n",
+                    chunk.getChunkId(), chunk.getChunkSizeMB());
+            DownloadWorker worker = new DownloadWorker(chunk, config);
+            worker.run(); // blocks until this chunk is fully "downloaded"
+            System.out.printf("[Sequential] Chunk #%d done in %.2fs%n",
+                    chunk.getChunkId(), chunk.getDownloadDurationMs() / 1000.0);
+        }
+
+        return System.currentTimeMillis() - start;
+    }
+}