develop

.idea/misc.xml

@@ -8,7 +8,5 @@
       </list>
     </option>
   </component>
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_21" default="true" project-jdk-name="21" project-jdk-type="JavaSDK">
-    <output url="file://$PROJECT_DIR$/out" />
-  </component>
+  <component name="ProjectRootManager" version="2" project-jdk-name="21" project-jdk-type="JavaSDK" />
 </project>

Report.md

@@ -0,0 +1,65 @@
+# Assignment Report: Multithreading Basics
+### Course: Advanced Programming
+
+## Assignment: Eighth Assignment – Multithreading Basics
+
+Project: Simulated Download Manager
+
+1. Theoretical Questions
+   1.1 Difference Between start() and run()
+   In Java, the run() method contains the code that a thread should execute. However, calling run() directly does not create a new thread; it works like a normal method call in the current thread.
+
+When start() is called, the JVM creates a new thread, which then executes the run() method internally.
+
+1.2 Daemon Threads
+A daemon thread is a background thread. The JVM does not wait for daemon threads to finish. When all user threads finish, the JVM stops the program even if daemon threads are still running.
+
+If setDaemon(true) is removed, the thread becomes a normal user thread, and the JVM will wait for it to complete.
+
+1.3 Lambda Expressions for Threads
+A lambda expression is a concise way to implement a functional interface like Runnable. Since Runnable has only one method (run()), we can use:
+
+() -> { ... } instead of creating a whole new class.
+
+2. Practical Implementation
+   2.1 Project Overview
+   This project simulates a download manager where a file is divided into chunks, and each chunk is downloaded concurrently by separate worker threads.
+
+2.2 DownloadWorker
+The DownloadWorker class implements Runnable. It simulates the download of a single chunk by:
+
+Using random step sizes for download progress.
+Sleeping for random delays to simulate network latency.
+Updating its chunk status until the download is complete.
+2.3 ChunkStatus
+This class stores the state of each chunk, including its ID, size, and downloaded amount. Variables are marked as volatile to ensure visibility across different threads.
+
+2.4 ProgressMonitor
+The ProgressMonitor runs as a background thread to periodically check and print:
+
+Individual chunk progress.
+Total download percentage.
+A visual Progress Bar.
+Average download speed and ETA.
+2.5 Main Class
+The Main class coordinates the process:
+
+Reads configuration.
+Initializes chunks and worker threads.
+Starts the monitor and workers.
+Uses join() to wait for all threads to finish before printing the final report.
+3. Bonus Features
+   3.1 Progress Bar & ETA
+   A visual progress bar was added to the console output. The program also calculates the current speed in MB/s and estimates the remaining time (ETA) based on that speed.
+
+3.2 Sequential vs Multithreaded Comparison
+The program compares running the workers sequentially (using .run()) versus concurrently (using .start()). It calculates the Speedup to show how much faster multithreading is for this task.
+
+4. Execution Instructions
+   To compile and run the project, use the following commands:
+
+bash
+mvn compile
+mvn exec:java -Dexec.mainClass="Main"
+5. Conclusion
+   This project successfully demonstrates the power of multithreading in Java. By using separate threads for different chunks, the total download time is significantly reduced compared to a sequential approach.

src/main/java/ChunkStatus.java

@@ -7,7 +7,8 @@
  * Represents the state and download progress of a single file chunk.
  * Each worker thread updates its own ChunkStatus, while the monitor thread reads it.
  */
-public class ChunkStatus {
+public class ChunkStatus
+{
     private final int chunkId;
     private final double chunkSizeMB;
     private volatile double downloadedMB;
@@ -19,7 +20,8 @@ public class ChunkStatus {
      * Initializes a chunk with its unique ID and total allocated size.
      * Progress-related fields are initialized to default values.
      */
-    public ChunkStatus(int chunkId, double chunkSizeMB) {
+    public ChunkStatus(int chunkId, double chunkSizeMB)
+    {
         this.chunkId = chunkId;
         this.chunkSizeMB = chunkSizeMB;
         this.downloadedMB = 0.0;
@@ -28,49 +30,58 @@ public class ChunkStatus {
         this.endTimeMs = 0;
     }
 
-    // Getters and Setters
-    public int getChunkId() {
+    public int getChunkId()
+    {
         return chunkId;
     }
 
-    public double getChunkSizeMB() {
+    public double getChunkSizeMB()
+    {
         return chunkSizeMB;
     }
 
-    public double getDownloadedMB() {
+    public double getDownloadedMB()
+    {
         return downloadedMB;
     }
 
-    public void setDownloadedMB(double downloadedMB) {
-        // Guard to prevent downloaded size exceeding actual chunk size
-        if (downloadedMB >= this.chunkSizeMB) {
+    public void setDownloadedMB(double downloadedMB)
+    {
+        if (downloadedMB >= this.chunkSizeMB)
+        {
             this.downloadedMB = this.chunkSizeMB;
         } else {
             this.downloadedMB = downloadedMB;
         }
     }
 
-    public boolean isCompleted() {
+    public boolean isCompleted()
+    {
         return completed;
     }
 
-    public void setCompleted(boolean completed) {
+    public void setCompleted(boolean completed)
+    {
         this.completed = completed;
     }
 
-    public long getStartTimeMs() {
+    public long getStartTimeMs()
+    {
         return startTimeMs;
     }
 
-    public void setStartTimeMs(long startTimeMs) {
+    public void setStartTimeMs(long startTimeMs)
+    {
         this.startTimeMs = startTimeMs;
     }
 
-    public long getEndTimeMs() {
+    public long getEndTimeMs()
+    {
         return endTimeMs;
     }
 
-    public void setEndTimeMs(long endTimeMs) {
+    public void setEndTimeMs(long endTimeMs)
+    {
         this.endTimeMs = endTimeMs;
     }
 
@@ -78,8 +89,10 @@ public class ChunkStatus {
      * Helper method to calculate the duration of this specific chunk's download.
      * Returns 0 if the chunk hasn't started or finished yet.
      */
-    public long getDownloadDurationMs() {
-        if (startTimeMs > 0 && endTimeMs > startTimeMs) {
+    public long getDownloadDurationMs()
+    {
+        if (startTimeMs > 0 && endTimeMs > startTimeMs)
+        {
             return endTimeMs - startTimeMs;
         } else if (startTimeMs > 0 && !completed) {
             return System.currentTimeMillis() - startTimeMs;
@@ -90,13 +103,15 @@ public class ChunkStatus {
     /**
      * Helper method to calculate the download percentage of this chunk.
      */
-    public double getProgressPercentage() {
+    public double getProgressPercentage()
+    {
         if (chunkSizeMB == 0) return 100.0;
         return (downloadedMB / chunkSizeMB) * 100.0;
     }
 
     @Override
-    public String toString() {
+    public String toString()
+    {
         return String.format("Chunk #%d: %.1f/%.1f MB (%.1f%%)%s",
                 chunkId,
                 downloadedMB,

src/main/java/DownloadWorker.java

@@ -7,37 +7,99 @@ import java.util.Random;
  * The main multithreading and simulation logic should be completed
  * in the run() method.</p>
  */
-public class DownloadWorker implements Runnable {
+public class DownloadWorker implements Runnable
+{
 
     private final ChunkStatus chunkStatus;
     private final DownloadConfig config;
     private final Random random;
 
-    public DownloadWorker(ChunkStatus chunkStatus, DownloadConfig config) {
+    public DownloadWorker(ChunkStatus chunkStatus, DownloadConfig config)
+    {
         this.chunkStatus = chunkStatus;
         this.config = config;
         this.random = new Random();
     }
 
     @Override
-    public void run() {
+    public void run()
+    {
+
+        long startTime = System.currentTimeMillis();
         // TODO: Record the chunk start time in chunkStatus.
+        chunkStatus.setStartTimeMs(System.currentTimeMillis());
         double downloaded = 0.0;
 
         // TODO: Print a message that this chunk has started downloading.
+        System.out.println("Chunk #" + chunkStatus.getChunkId() + " started downloading.");
 
-        while (downloaded < chunkStatus.getChunkSizeMB()) {
+        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.
+
+            int delay = config.getMinStepDelayMs()
+                    + random.nextInt(config.getMaxStepDelayMs() - config.getMinStepDelayMs() + 1);
+
+            try
+            {
+                Thread.sleep(delay);
+            } catch (InterruptedException e)
+            {
+                Thread.currentThread().interrupt();
+                return;
+            }
+
+            double step = config.getMinStepDownloadMB()
+                    + random.nextDouble() * (config.getMaxStepDownloadMB() - config.getMinStepDownloadMB());
+
+            downloaded += step;
+
+            if (downloaded > chunkStatus.getChunkSizeMB())
+            {
+                downloaded = chunkStatus.getChunkSizeMB();
+            }
+
+            chunkStatus.setDownloadedMB(downloaded);
+
+            System.out.printf(
+                    "Chunk #%d progress: %.2f / %.2f MB (%.2f%%)%n",
+                    chunkStatus.getChunkId(),
+                    downloaded,
+                    chunkStatus.getChunkSizeMB(),
+                    chunkStatus.getProgressPercentage()
+            );
         }
 
         // TODO: Mark the chunk as completed.
         // TODO: Record the chunk end time in chunkStatus.
         // TODO: Print a message that this chunk has finished downloading.
+
+        chunkStatus.setCompleted(true);
+
+        chunkStatus.setEndTimeMs(System.currentTimeMillis());
+
+        long endTime = chunkStatus.getEndTimeMs();
+        long start = chunkStatus.getStartTimeMs();
+
+        double seconds = (endTime - start) / 1000.0;
+
+        double averageSpeed = 0.0;
+        if (seconds > 0)
+        {
+            averageSpeed = chunkStatus.getChunkSizeMB() / seconds;
+        }
+
+        System.out.printf(
+                "Chunk #%d finished in %.2f seconds | Avg speed: %.2f MB/s%n",
+                chunkStatus.getChunkId(),
+                seconds,
+                averageSpeed
+        );
     }
 
 }

src/main/java/Main.java

@@ -1,15 +1,22 @@
 import java.util.ArrayList;
 import java.util.List;
 
-public class Main {
-    public static void main(String[] args) {
+public class Main
+{
+
+    public static void main(String[] args)
+    {
+
         System.out.println("=== Simulated Download Manager ===");
 
-        // 1. Read config
         DownloadConfig config;
-        try {
+
+        try
+        {
             config = ConfigReader.readConfig("download_config.txt");
-        } catch (Exception e) {
+        }
+        catch (Exception e)
+        {
             System.out.println("Failed to read configuration: " + e.getMessage());
             return;
         }
@@ -19,75 +26,138 @@ public class Main {
         System.out.println("Chunk count: " + config.getChunkCount());
         System.out.println();
 
-        // 2. Create chunks
+        System.out.println("======================================");
+        System.out.println("Running Sequential Simulation");
+        System.out.println("======================================");
+
+        SimulationResult sequentialResult = runSimulation(config, true);
+
+        System.out.println();
+        System.out.println("======================================");
+        System.out.println("Running Multithreaded Simulation");
+        System.out.println("======================================");
+
+        SimulationResult multithreadedResult = runSimulation(config, false);
+
+        System.out.println();
+        System.out.println("======================================");
+        System.out.println("Performance Comparison");
+        System.out.println("======================================");
+
+        System.out.printf("Sequential time: %.2f seconds%n", sequentialResult.totalSeconds);
+        System.out.printf("Sequential average speed: %.2f MB/s%n", sequentialResult.averageSpeed);
+
+        System.out.printf("Multithreaded time: %.2f seconds%n", multithreadedResult.totalSeconds);
+        System.out.printf("Multithreaded average speed: %.2f MB/s%n", multithreadedResult.averageSpeed);
+
+        if (multithreadedResult.totalSeconds > 0)
+        {
+            double speedup = sequentialResult.totalSeconds / multithreadedResult.totalSeconds;
+            System.out.printf("Speedup: %.2fx faster%n", speedup);
+        }
+
+        System.out.println("======================================");
+        System.out.println("Simulation finished.");
+    }
+
+    private static SimulationResult runSimulation(DownloadConfig config, boolean sequentialMode)
+    {
+
+        long programStartTime = System.currentTimeMillis();
+
         List<ChunkStatus> chunks = ChunkUtils.createChunks(
                 config.getTotalSizeMB(),
                 config.getChunkCount()
         );
 
-        // 3. Create worker threads
         List<Thread> workerThreads = new ArrayList<>();
 
-        for (ChunkStatus chunk : chunks) {
+        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.
+            System.out.println(
+                    "Assigned Chunk " + chunk.getChunkId()
+                            + " (" + chunk.getChunkSizeMB() + " MB)"
+                            + " to " + workerThread.getName()
+            );
         }
 
-        // 4. Create and start monitor thread
+        System.out.println();
+
         ProgressMonitor monitor = new ProgressMonitor(config, chunks);
         Thread monitorThread = new Thread(monitor, "Progress-Monitor");
 
-        // TODO:
-        // Start the monitor thread before starting the workers
-        // so that progress can be displayed while downloading happens.
-        //
-        // Example idea:
-        // monitorThread.start();
+        monitorThread.start();
 
-        // 5. Start worker threads
-        // TODO:
-        // Start each worker thread in workerThreads.
-        // Use a loop and call start() on each thread.
+        if (sequentialMode)
+        {
 
-        // 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();
-        // }
+            System.out.println("Mode: SEQUENTIAL");
+            System.out.println();
 
-        // 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,
+            for (Thread workerThread : workerThreads)
+            {
+                workerThread.run();
+            }
+
+        }
+        else
+        {
+
+            System.out.println("Mode: MULTITHREADED");
+            System.out.println();
+
+            for (Thread workerThread : workerThreads)
+            {
+                workerThread.start();
+            }
+
+            try
+            {
+                for (Thread workerThread : workerThreads)
+                {
+                    workerThread.join();
+                }
+            }
+            catch (InterruptedException e)
+            {
+                Thread.currentThread().interrupt();
+                System.out.println("Main thread interrupted while waiting for workers.");
+                return new SimulationResult(0.0, 0.0);
+            }
+        }
+
+        try
+        {
+            monitorThread.join();
+        }
+        catch (InterruptedException e)
+        {
+            Thread.currentThread().interrupt();
+            System.out.println("Main thread interrupted while waiting for monitor.");
+            return new SimulationResult(0.0, 0.0);
+        }
+
+        long programEndTime = System.currentTimeMillis();
+        double totalSeconds = (programEndTime - programStartTime) / 1000.0;
 
-        // 7. Print final report
         System.out.println();
         System.out.println("=== Final Report ===");
 
         int completedChunks = 0;
         double downloadedMB = 0.0;
 
-        for (ChunkStatus chunk : chunks) {
+        for (ChunkStatus chunk : chunks)
+        {
             downloadedMB += chunk.getDownloadedMB();
 
-            if (chunk.isCompleted()) {
+            if (chunk.isCompleted())
+            {
                 completedChunks++;
             }
 
@@ -100,8 +170,34 @@ public class Main {
         }
 
         System.out.println();
+
+        System.out.println("Mode: " + (sequentialMode ? "Sequential" : "Multithreaded"));
         System.out.println("Completed chunks: " + completedChunks + "/" + chunks.size());
         System.out.println("Downloaded total: " + downloadedMB + "/" + config.getTotalSizeMB() + " MB");
-        System.out.println("Simulation finished.");
+
+        System.out.printf("Total download time: %.2f seconds%n", totalSeconds);
+
+        double overallSpeed = 0.0;
+        if (totalSeconds > 0)
+        {
+            overallSpeed = config.getTotalSizeMB() / totalSeconds;
+        }
+
+        System.out.printf("Overall average speed: %.2f MB/s%n", overallSpeed);
+
+        return new SimulationResult(totalSeconds, overallSpeed);
     }
-}
+
+    private static class SimulationResult
+    {
+
+        private final double totalSeconds;
+        private final double averageSpeed;
+
+        public SimulationResult(double totalSeconds, double averageSpeed)
+        {
+            this.totalSeconds = totalSeconds;
+            this.averageSpeed = averageSpeed;
+        }
+    }
+}

src/main/java/ProgressMonitor.java

@@ -1,69 +1,128 @@
 import java.util.List;
 
-public class ProgressMonitor implements Runnable {
+public class ProgressMonitor implements Runnable
+{
 
     private final String fileName;
     private final int totalSizeMB;
     private final List<ChunkStatus> chunks;
     private final long monitorDelayMs;
+    private long monitorStartTime;
 
-    public ProgressMonitor(DownloadConfig config, List<ChunkStatus> chunks) {
+    public ProgressMonitor(DownloadConfig config, List<ChunkStatus> chunks)
+    {
         this.fileName = config.getFileName();
         this.totalSizeMB = config.getTotalSizeMB();
         this.chunks = chunks;
         this.monitorDelayMs = 500;
     }
 
+    private String createProgressBar(double percent)
+    {
+        int width = 30;
+        int filled = (int) (percent / 100 * width);
+
+        StringBuilder bar = new StringBuilder("[");
+        for (int i = 0; i < width; i++)
+        {
+            if (i < filled) {
+                bar.append("#");
+            } else {
+                bar.append("-");
+            }
+        }
+        bar.append("]");
+
+        return bar.toString();
+    }
+
     @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
 
+    public void run()
+    {
 
-        while (true) {
+        monitorStartTime = System.currentTimeMillis();
+
+        while (true)
+        {
             double totalDownloadedMB = 0.0;
             int completedChunks = 0;
 
-            for (ChunkStatus chunk : chunks) {
+            for (ChunkStatus chunk : chunks)
+            {
                 totalDownloadedMB += chunk.getDownloadedMB();
 
-                if (chunk.isCompleted()) {
+                if (chunk.isCompleted())
+                {
                     completedChunks++;
                 }
             }
 
             double percent = 0.0;
-            if (totalSizeMB > 0) {
+            if (totalSizeMB > 0)
+            {
                 percent = (totalDownloadedMB * 100.0) / totalSizeMB;
             }
 
+            long currentTime = System.currentTimeMillis();
+            double elapsedSeconds = (currentTime - monitorStartTime) / 1000.0;
+
+            double currentSpeed = 0.0;
+            if (elapsedSeconds > 0)
+            {
+                currentSpeed = totalDownloadedMB / elapsedSeconds;
+            }
+
+            double remainingMB = totalSizeMB - totalDownloadedMB;
+
+            double etaSeconds = 0.0;
+            if (currentSpeed > 0)
+            {
+                etaSeconds = remainingMB / currentSpeed;
+            }
+
+            System.out.println("--------------------------------------------------");
+            for (ChunkStatus chunk : chunks)
+            {
+                System.out.printf(
+                        "Chunk %d: %.1f MB downloaded %s%n",
+                        chunk.getChunkId(),
+                        chunk.getDownloadedMB(),
+                        chunk.getChunkSizeMB(),
+                        chunk.isCompleted() ? "(Completed ✅)" : ""
+                );
+            }
+
             System.out.printf(
-                    "Progress for %s: %.1f/%.1f MB (%.2f%%), completed chunks: %d/%d%n",
+                    "Total Progress for %s: %s %.2f%% (%d/%d chunks)%n",
                     fileName,
-                    totalDownloadedMB,
-                    (double) totalSizeMB,
+                    createProgressBar(percent),
                     percent,
                     completedChunks,
-                    chunks.size()
+                    chunks.size(),
+                    currentSpeed,
+                    etaSeconds
             );
 
+            if (completedChunks == chunks.size())
+            {
+                System.out.println(">>> Monitor: All chunks finished. Download complete.");
+                System.out.println("==================================================");
+                break;
+            }
 
-            // TODO:
-            // If all chunks are completed, print a final message and exit the loop
-
-            try {
+            try
+            {
                 Thread.sleep(monitorDelayMs);
-            } catch (InterruptedException e) {
+            }
+            catch (InterruptedException e)
+            {
+                Thread.currentThread().interrupt();
                 System.out.println("Progress monitor interrupted.");
                 return;
             }
         }
+
     }
+
 }