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+++ b/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}
diff --git a/src/main/java/DownloadWorker.java b/src/main/java/DownloadWorker.java
index 546de2d..201330b 100644
--- a/src/main/java/DownloadWorker.java
+++ b/src/main/java/DownloadWorker.java
@@ -2,10 +2,7 @@ import java.util.Random;
/**
* Simulates downloading a single chunk of a file.
- *
- * This class is intentionally provided as a skeleton for students.
- * The main multithreading and simulation logic should be completed
- * in the run() method.
+ * 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);
}
-
}
diff --git a/src/main/java/Main.java b/src/main/java/Main.java
index 82bd239..decd7b3 100644
--- a/src/main/java/Main.java
+++ b/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 chunks = ChunkUtils.createChunks(
- config.getTotalSizeMB(),
- config.getChunkCount()
- );
+ config.getTotalSizeMB(), config.getChunkCount());
- // 3. Create worker threads
+ // 3. Create one worker thread per chunk
List 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 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.");
}
}
diff --git a/src/main/java/ProgressMonitor.java b/src/main/java/ProgressMonitor.java
index 475c0e0..ec48477 100644
--- a/src/main/java/ProgressMonitor.java
+++ b/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 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 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 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;
+ }
}
diff --git a/src/main/java/SequentialDownloader.java b/src/main/java/SequentialDownloader.java
new file mode 100644
index 0000000..3555571
--- /dev/null
+++ b/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 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;
+ }
+}