8th Home Work, Practical and Theoretical Questions
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\documentclass[12pt,a4paper]{article}
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\usepackage[utf8]{inputenc}
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\usepackage[T1]{fontenc}
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\usepackage[margin=2.5cm]{geometry}
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\usepackage{listings}
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\usepackage{xcolor}
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\usepackage{hyperref}
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\usepackage{parskip}
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\usepackage{booktabs}
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\usepackage{array}
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\usepackage{titlesec}
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\usepackage{fancyhdr}
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\usepackage{amsmath}
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\usepackage{enumitem}
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% ── Page style ──────────────────────────────────────────────────────────────
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\pagestyle{fancy}
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\fancyhf{}
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\rhead{Advanced Programming – Assignment 8}
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\lhead{Faraz Ardeh}
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\cfoot{\thepage}
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% ── Section formatting ───────────────────────────────────────────────────────
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\titleformat{\section}{\large\bfseries}{Question \thesection.}{0.6em}{}
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\titleformat{\subsection}{\normalsize\bfseries}{}{0em}{}
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% ── Java code style ─────────────────────────────────────────────────────────
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\lstdefinestyle{java}{
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language=Java,
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basicstyle=\ttfamily\small,
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keywordstyle=\color{javakw}\bfseries,
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stringstyle=\color{javastr},
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commentstyle=\color{javacmt}\itshape,
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numberstyle=\tiny\color{gray},
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numbers=left,
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stepnumber=1,
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numbersep=8pt,
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backgroundcolor=\color{codebg},
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frame=single,
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breaklines=true,
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tabsize=4,
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captionpos=b,
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}
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\lstset{style=java}
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% ── Inline code ─────────────────────────────────────────────────────────────
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\newcommand{\code}[1]{\texttt{\small #1}}
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% ────────────────────────────────────────────────────────────────────────────
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\begin{document}
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% ── Title page ───────────────────────────────────────────────────────────────
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\begin{titlepage}
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\centering
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\vspace*{3cm}
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{\Huge\bfseries Multithreading Basics\par}
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\vspace{0.8cm}
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{\large Assignment 8 – Theoretical Questions\par}
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\vspace{0.4cm}
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{\large Advanced Programming (AP)\par}
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\vspace{2cm}
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\rule{0.6\linewidth}{0.5pt}\\[0.4cm]
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{\large\bfseries Faraz Ardeh\par}
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\vspace{0.3cm}
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{\normalsize fa.ardeh@gmail.com\par}
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\vspace{0.6cm}
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{\normalsize Shahid Beheshti University\par}
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\vspace{0.3cm}
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{\normalsize June 2026\par}
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\vfill
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\end{titlepage}
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\tableofcontents
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\newpage
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% ════════════════════════════════════════════════════════════════════════════
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\section{\code{start()} vs \code{run()}}
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% ════════════════════════════════════════════════════════════════════════════
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The program under analysis:
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\begin{lstlisting}[caption={StartVsRun.java}]
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public class StartVsRun {
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static class MyRunnable implements Runnable {
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public void run() {
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System.out.println("Running in: " + Thread.currentThread().getName());
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}
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}
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public static void main(String[] args) throws InterruptedException {
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Thread t1 = new Thread(new MyRunnable(), "Thread-1");
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System.out.println("Calling run()");
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t1.run();
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Thread.sleep(100);
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Thread t2 = new Thread(new MyRunnable(), "Thread-2");
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System.out.println("Calling start()");
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t2.start();
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}
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}
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\end{lstlisting}
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\subsection{Expected output}
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\begin{lstlisting}[language={},numbers=none,backgroundcolor=\color{codebg}]
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Calling run()
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Running in: main
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Calling start()
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Running in: Thread-2
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\end{lstlisting}
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\subsection{Why this output?}
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\textbf{The \code{t1.run()} call:}
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Calling \code{run()} on a \code{Thread} object is just an ordinary method call, exactly
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like calling any other method on any other object.
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No new OS thread is created or scheduled.
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The body of \code{run()} executes \emph{synchronously} inside the calling thread,
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which is \code{main}.
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Therefore \code{Thread.currentThread().getName()} returns \texttt{"main"},
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not \texttt{"Thread-1"}.
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The thread object \texttt{t1} was constructed but its native thread was never started.
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\textbf{The \code{t2.start()} call:}
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\code{start()} allocates a new OS-level thread, registers it with the JVM scheduler,
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and returns to the caller \emph{immediately} (it does not wait for \code{run()} to finish).
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The new thread then invokes \code{run()} autonomously and concurrently.
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Inside that new thread, \code{Thread.currentThread().getName()} correctly
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returns \texttt{"Thread-2"}.
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\subsection{Key differences at a glance}
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\begin{center}
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\begin{tabular}{>{\bfseries}lll}
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\toprule
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Aspect & \code{run()} & \code{start()} \\
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\midrule
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New thread created? & No & Yes (exactly one) \\
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Execution thread & Current thread & New thread \\
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Blocking behaviour & Synchronous (caller waits) & Asynchronous (returns at once) \\
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Can be called twice? & Yes, legal & No – throws \code{IllegalThreadStateException} \\
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Useful for? & Testing \code{run()} logic directly & True concurrent execution \\
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\bottomrule
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\end{tabular}
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\end{center}
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\textbf{Summary:}
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\code{run()} is simply a method call; \code{start()} is what actually creates and
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launches a new thread of execution. Calling \code{run()} instead of \code{start()} is
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one of the most common multithreading bugs in Java – the code compiles and
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"works", but no concurrency ever happens.
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% ════════════════════════════════════════════════════════════════════════════
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\section{Daemon Threads}
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% ════════════════════════════════════════════════════════════════════════════
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\begin{lstlisting}[caption={DaemonExample.java}]
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public class DaemonExample {
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static class DaemonRunnable implements Runnable {
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public void run() {
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for (int i = 0; i < 20; i++) {
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System.out.println("Daemon thread running...");
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try {
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Thread.sleep(500);
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} catch (InterruptedException e) {
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// [Handling Exception...]
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}
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}
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}
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}
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public static void main(String[] args) {
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Thread thread = new Thread(new DaemonRunnable());
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thread.setDaemon(true);
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thread.start();
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System.out.println("Main thread ends.");
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}
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}
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\end{lstlisting}
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\subsection{Expected output (with \code{setDaemon(true)})}
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\begin{lstlisting}[language={},numbers=none,backgroundcolor=\color{codebg}]
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Main thread ends.
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Daemon thread running...
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(program terminates -- usually 0-2 more lines, non-deterministic)
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\end{lstlisting}
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\textbf{Why?}
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The JVM shuts down when there are no \emph{non-daemon} threads still alive.
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After \code{main()} prints \texttt{"Main thread ends."} and returns, the only surviving
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thread is the daemon thread.
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Because it is marked as a daemon, the JVM does \emph{not} wait for it to
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finish – it exits immediately (or after one scheduling quantum), abruptly
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terminating the daemon thread.
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The daemon may manage to print zero, one, or a few lines before termination,
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depending entirely on OS thread scheduling; this is non-deterministic.
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\subsection{What happens if you remove \code{thread.setDaemon(true)}?}
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Without that call the thread becomes a regular \emph{user thread} (the default).
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The JVM rule is: \textbf{wait for all user threads to finish before exiting.}
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The daemon thread (now a user thread) will sleep 500 ms per iteration and
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loop 20 times – the program will take approximately $20 \times 0.5 = 10$ seconds
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to terminate, and all 20 lines of \texttt{"Daemon thread running..."} will be
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printed in full before the JVM exits.
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\subsection{Real-life use cases of daemon threads}
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Daemon threads are ideal for background housekeeping work that should not
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prevent the application from exiting cleanly.
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\begin{enumerate}[leftmargin=2em]
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\item \textbf{Garbage Collection.}
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The JVM's garbage collector runs as a daemon thread;
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it must not keep the JVM alive on its own.
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\item \textbf{Log flushing.}
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A background thread that periodically flushes buffered log entries
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to disk. If the application finishes, unsaved logs are
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an acceptable loss compared with hanging the process.
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\item \textbf{Cache invalidation / expiry.}
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A thread that sweeps an in-memory cache and removes stale entries
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does not need to outlive the application.
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\item \textbf{Heartbeat / health-check threads.}
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Service-mesh sidecars and microservices often send periodic
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pings to a service-discovery system.
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These should die with the service, not keep it alive.
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\item \textbf{IDE background indexing.}
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IntelliJ IDEA's indexer and VS Code's language-server workers
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are typically daemon-like: if you close the IDE, you do not
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want to wait for them to finish indexing.
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\end{enumerate}
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% ════════════════════════════════════════════════════════════════════════════
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\section{A Shorter Way to Create Threads – Lambda Expressions}
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% ════════════════════════════════════════════════════════════════════════════
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\begin{lstlisting}[caption={ThreadDemo.java}]
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public class ThreadDemo {
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public static void main(String[] args) {
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Thread thread = new Thread(() -> {
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System.out.println("Thread is running using a lambda!");
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});
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thread.start();
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}
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}
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\end{lstlisting}
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\subsection{Expected output}
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\begin{lstlisting}[language={},numbers=none,backgroundcolor=\color{codebg}]
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Thread is running using a lambda!
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\end{lstlisting}
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\subsection{What is \code{() -> \{ \ldots \}} called?}
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The \code{() -> \{ \ldots \}} syntax is called a \textbf{lambda expression}
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(also known as an \emph{anonymous function} or \emph{arrow function} in
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other languages).
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A lambda expression is a concise way to provide an implementation of a
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\emph{functional interface} – any interface that declares exactly one abstract
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method.
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\code{Runnable} is a functional interface: its single abstract method is
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\code{void run()}.
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The lambda \code{() -> \{ \ldots \}} supplies that implementation inline,
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without naming it.
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\subsection{How does this differ from other approaches?}
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There are three common ways to supply a \code{Runnable} to a \code{Thread}:
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\begin{lstlisting}[caption={Three equivalent approaches}]
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// 1. Class that extends Thread
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class MyThread extends Thread {
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public void run() { System.out.println("extends Thread"); }
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}
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new MyThread().start();
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// 2. Named class that implements Runnable
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class MyRunnable implements Runnable {
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public void run() { System.out.println("implements Runnable"); }
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}
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new Thread(new MyRunnable()).start();
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// 3. Lambda expression (shortest)
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new Thread(() -> System.out.println("lambda")).start();
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\end{lstlisting}
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\begin{center}
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\begin{tabular}{>{\bfseries}lllll}
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\toprule
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Approach & Boilerplate & Separate class? & Captures outer vars? & Extensible? \\
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\midrule
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\code{extends Thread} & High & Yes (named) & No & Inherits Thread \\
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\code{implements Runnable} & Medium & Yes (named) & No & Yes \\
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Anonymous class & Medium & Yes (anon.) & Yes (eff.\ final) & Yes \\
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Lambda & \textbf{Minimal} & No & Yes (eff.\ final) & No \\
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\bottomrule
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\end{tabular}
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\end{center}
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\textbf{Key advantages of lambdas:}
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\begin{itemize}[leftmargin=2em]
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\item \textbf{Conciseness.}
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No need to declare a class, override a method, or write a constructor.
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A single line can create and start a thread.
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\item \textbf{Readability.}
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The intent (``run this block of code in a new thread'') is immediately
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obvious to the reader.
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\item \textbf{Variable capture.}
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A lambda can reference local variables from the enclosing scope as long
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as they are effectively final (i.e., never reassigned after declaration).
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This is often more convenient than passing data through a constructor.
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\item \textbf{Functional programming patterns.}
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Lambdas work seamlessly with the Java Streams API, \code{CompletableFuture},
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\code{ExecutorService}, and other modern concurrency utilities that accept
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\code{Runnable} or \code{Callable} arguments.
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\end{itemize}
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\textbf{Limitation:}
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Because a lambda is not a subclass of \code{Thread}, it cannot override thread
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life-cycle methods such as \code{interrupt()} or \code{setUncaughtExceptionHandler()}
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directly inside the lambda body.
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When that level of control is needed, a named class is more appropriate.
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% ── Footer note ──────────────────────────────────────────────────────────────
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\vfill
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\begin{center}
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\small\color{gray}
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Advanced Programming – Assignment 8 \quad|\quad
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Faraz Ardeh \quad|\quad
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Shahid Beheshti University \quad|\quad
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June 2026
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\end{center}
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\end{document}
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@@ -2,10 +2,7 @@ import java.util.Random;
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/**
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* Simulates downloading a single chunk of a file.
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*
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* <p>This class is intentionally provided as a skeleton for students.
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* The main multithreading and simulation logic should be completed
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* in the run() method.</p>
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* Each worker writes only to its own assigned ChunkStatus object.
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*/
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public class DownloadWorker implements Runnable {
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@@ -21,23 +18,33 @@ public class DownloadWorker implements Runnable {
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@Override
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public void run() {
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// TODO: Record the chunk start time in chunkStatus.
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double downloaded = 0.0;
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||||
// Record the start time for this chunk
|
||||
chunkStatus.setStartTimeMs(System.currentTimeMillis());
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||||
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// TODO: Print a message that this chunk has started downloading.
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double downloaded = 0.0;
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int delayRange = config.getMaxStepDelayMs() - config.getMinStepDelayMs();
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double stepRange = config.getMaxStepDownloadMB() - config.getMinStepDownloadMB();
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||||
|
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while (downloaded < chunkStatus.getChunkSizeMB()) {
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||||
// TODO: Generate a random sleep delay between min and max delay.
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||||
// TODO: Sleep for that delay.
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||||
// TODO: Generate a random download amount for this step.
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// TODO: Increase downloaded, but do not go beyond chunk size.
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// TODO: Save the updated downloaded value into chunkStatus.
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||||
// TODO: Optionally print step-by-step progress.
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||||
// Random delay simulating network latency for this step
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||||
int delay = config.getMinStepDelayMs() + (delayRange > 0 ? random.nextInt(delayRange) : 0);
|
||||
try {
|
||||
Thread.sleep(delay);
|
||||
} catch (InterruptedException e) {
|
||||
Thread.currentThread().interrupt();
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||||
return;
|
||||
}
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||||
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||||
// TODO: Mark the chunk as completed.
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||||
// TODO: Record the chunk end time in chunkStatus.
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// TODO: Print a message that this chunk has finished downloading.
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||||
// Random amount downloaded in this step, capped at remaining size
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||||
double step = config.getMinStepDownloadMB() + random.nextDouble() * stepRange;
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||||
downloaded = Math.min(downloaded + step, chunkStatus.getChunkSizeMB());
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||||
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||||
// Write only to this worker's own ChunkStatus (thread-safe by design)
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||||
chunkStatus.setDownloadedMB(downloaded);
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||||
}
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||||
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||||
// Mark completion and record end time
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||||
chunkStatus.setEndTimeMs(System.currentTimeMillis());
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||||
chunkStatus.setCompleted(true);
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||||
}
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||||
}
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||||
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||||
+72
-68
@@ -3,7 +3,7 @@ import java.util.List;
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||||
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||||
public class Main {
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||||
public static void main(String[] args) {
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||||
System.out.println("=== Simulated Download Manager ===");
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||||
System.out.println("=== Simulated Download Manager ===\n");
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||||
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||||
// 1. Read config
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||||
DownloadConfig config;
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||||
@@ -14,94 +14,98 @@ public class Main {
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||||
return;
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||||
}
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||||
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||||
System.out.println("File name: " + config.getFileName());
|
||||
System.out.println("Total size (MB): " + config.getTotalSizeMB());
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||||
System.out.println("Chunk count: " + config.getChunkCount());
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||||
System.out.println("File name : " + config.getFileName());
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||||
System.out.println("Total size : " + config.getTotalSizeMB() + " MB");
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||||
System.out.println("Chunks : " + config.getChunkCount());
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||||
System.out.println("Step delay : " + config.getMinStepDelayMs()
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||||
+ "–" + config.getMaxStepDelayMs() + " ms");
|
||||
System.out.println("Step size : " + config.getMinStepDownloadMB()
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||||
+ "–" + 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++;
|
||||
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);
|
||||
|
||||
System.out.println(
|
||||
"Chunk " + chunk.getChunkId()
|
||||
+ ": " + chunk.getDownloadedMB()
|
||||
+ "/" + chunk.getChunkSizeMB()
|
||||
+ " MB"
|
||||
);
|
||||
}
|
||||
// ── 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.");
|
||||
}
|
||||
}
|
||||
|
||||
@@ -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;
|
||||
}
|
||||
}
|
||||
|
||||
@@ -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;
|
||||
}
|
||||
}
|
||||
Reference in New Issue
Block a user