Assignment-8

Report.md

@@ -0,0 +1,115 @@
+### 1. `start()` vs `run()`
+
+``` java
+public class StartVsRun {    
+    static class MyRunnable implements Runnable {    
+        public void run() {    
+            System.out.println("Running in: " + Thread.currentThread().getName()); 
+        }    
+    }    
+    public static void main(String[] args) throws InterruptedException {    
+        Thread t1 = new Thread(new MyRunnable(), "Thread-1");    
+        System.out.println("Calling run()");    
+        t1.run();    
+        Thread.sleep(100);    
+    
+        Thread t2 = new Thread(new MyRunnable(), "Thread-2");    
+        System.out.println("Calling start()");    
+        t2.start();    
+    }  
+}
+```
+
+#### What output do you get from the program? Why?
+- The output is:
+```
+Calling run()
+Running in: main
+Calling start()
+Running in: Thread-2
+```
+Since `t1.run()` executes the `run()` method directly inside the main thread, but `t2.start()` executes it inside the created new thread.
+
+#### What’s the difference in behavior between calling `start()` and `run()`?
+- Calling `run()` is just a normal method call, so the program waits for it to finish before moving to the next line. 
+  
+  Calling `start()` tells Java to create a new thread and execute the `run()` method inside it, which allows it to run alongside the main thread.
+
+---
+### 2. Daemon Threads
+
+``` java
+public class DaemonExample {    
+    static class DaemonRunnable implements Runnable {    
+        public void run() {    
+            for(int i = 0; i < 20; i++) {    
+                System.out.println("Daemon thread running...");    
+                try {    
+                    Thread.sleep(500);    
+                } catch (InterruptedException e) {    
+                 //[Handling Exception...]  
+                }            
+            }    
+        }    
+    }    
+    public static void main(String[] args) {    
+        Thread thread = new Thread(new DaemonRunnable());    
+        thread.setDaemon(true);    
+        thread.start();    
+        System.out.println("Main thread ends.");    
+    }  
+}
+```
+
+#### What output do you get from the program? Why?
+- The output is:
+```
+Main thread ends.
+Daemon thread running...
+```
+Since `thread.setDaemon(true)` marks the thread as a background "daemon" thread, the program ends as soon as all user (non-daemon) threads (the main thread in this case) have finished, regardless of whether the daemon thread has completed its task.
+
+#### What happens if you remove `thread.setDaemon(true)`?
+- The program continues printing `Daemon thread running...` 20 times even after the main thread has finished.
+```
+Main thread ends.
+Daemon thread running...
+.
+.
+.
+Daemon thread running...
+```
+
+#### What are some real-life use cases of daemon threads?
+- In general, when we want a background task to run **only** while the main program is running, we use daemon threads.
+
+  For example, background tasks like cache clearing, checking connectivity to a server, or monitoring CPU/Memory usage can all be done using daemon threads.
+
+---
+### 3. A shorter way to create threads
+
+``` java
+public class ThreadDemo {  
+    public static void main(String[] args) {  
+        Thread thread = new Thread(() -> {  
+            System.out.println("Thread is running using a ...!");  
+        });  
+  
+        thread.start();  
+    }  
+}
+```
+
+#### What output do you get from the program?
+- The output is:
+```
+Thread is running using a ...!
+```
+
+#### What is the () -> { ... } syntax called?
+- It's called a lambda expression
+
+#### How is this code different from creating a class that extends Thread or implements Runnable?
+- It’s much shorter and easier to read. Instead of having to define a new custom thread class (by extending Thread)
+or separate the task from the thread itself (by implementing Runnable) just to run a few lines of code,
+a lambda expression lets us pass the code directly to the thread.

src/main/java/ChunkStatus.java

@@ -1,12 +1,3 @@
-// Educational simplification:
-// each worker writes only to its own ChunkStatus,
-// and the monitor only reads chunk states.
-// volatile is used here to make progress updates more visible across threads.
-
-/**
- * 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 {
     private final int chunkId;
     private final double chunkSizeMB;
@@ -15,10 +6,7 @@ public class ChunkStatus {
     private volatile long startTimeMs;
     private volatile long endTimeMs;
 
-    /**
-     * 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) {
         this.chunkId = chunkId;
         this.chunkSizeMB = chunkSizeMB;
@@ -28,7 +16,7 @@ public class ChunkStatus {
         this.endTimeMs = 0;
     }
 
-    // Getters and Setters
+
     public int getChunkId() {
         return chunkId;
     }
@@ -42,7 +30,6 @@ public class ChunkStatus {
     }
 
     public void setDownloadedMB(double downloadedMB) {
-        // Guard to prevent downloaded size exceeding actual chunk size
         if (downloadedMB >= this.chunkSizeMB) {
             this.downloadedMB = this.chunkSizeMB;
         } else {
@@ -74,10 +61,7 @@ public class ChunkStatus {
         this.endTimeMs = endTimeMs;
     }
 
-    /**
-     * 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) {
             return endTimeMs - startTimeMs;
@@ -87,9 +71,7 @@ public class ChunkStatus {
         return 0;
     }
 
-    /**
-     * Helper method to calculate the download percentage of this chunk.
-     */
+
     public double getProgressPercentage() {
         if (chunkSizeMB == 0) return 100.0;
         return (downloadedMB / chunkSizeMB) * 100.0;

src/main/java/ChunkUtils.java

@@ -1,24 +1,14 @@
 import java.util.ArrayList;
 import java.util.List;
 
-/**
- * Utility methods related to chunk creation.
- */
+
 public class ChunkUtils {
 
     private ChunkUtils() {
-        // Utility class
+
     }
 
-    /**
-     * Splits the total file size into a list of chunks.
-     * Chunk sizes are as even as possible.
-     * If the size is not exactly divisible, the last chunk gets the remainder.
-     *
-     * @param totalSizeMB total file size in MB
-     * @param chunkCount number of chunks
-     * @return list of ChunkStatus objects
-     */
+
     public static List<ChunkStatus> createChunks(int totalSizeMB, int chunkCount) {
         List<ChunkStatus> chunks = new ArrayList<>();
 
@@ -36,8 +26,7 @@ public class ChunkUtils {
                 chunkSize += remainder;
             }
 
-            // Create one ChunkStatus object for each chunk.
-            // chunkId is the chunk number, and chunkSize is this chunk's total size.
+
             chunks.add(new ChunkStatus(i + 1, chunkSize));
         }
 

src/main/java/ConfigReader.java

@@ -63,7 +63,6 @@ public class ConfigReader {
                         maxStepDownloadMB = Double.parseDouble(value);
                         break;
                     default:
-                        // Ignore unknown keys to keep parsing simple
                         break;
                 }
             }

src/main/java/DownloadConfig.java

@@ -1,7 +1,3 @@
-/**
- * Represents the configuration parameters for the simulated download manager.
- * This class is immutable to ensure thread-safety when shared among worker threads.
- */
 public class DownloadConfig {
     private final String fileName;
     private final int totalSizeMB;
@@ -11,9 +7,7 @@ public class DownloadConfig {
     private final double minStepDownloadMB;
     private final double maxStepDownloadMB;
 
-    /**
-     * Constructs a new DownloadConfig with specified simulation parameters.
-     */
+
     public DownloadConfig(String fileName, int totalSizeMB, int chunkCount,
                           int minStepDelayMs, int maxStepDelayMs,
                           double minStepDownloadMB, double maxStepDownloadMB) {
@@ -26,7 +20,7 @@ public class DownloadConfig {
         this.maxStepDownloadMB = maxStepDownloadMB;
     }
 
-    // Getters
+
     public String getFileName() {
         return fileName;
     }

src/main/java/DownloadWorker.java

@@ -1,12 +1,6 @@
 import java.util.Random;
 
-/**
- * Simulates downloading a single chunk of a file.
- *
- * <p>This class is intentionally provided as a skeleton for students.
- * The main multithreading and simulation logic should be completed
- * in the run() method.</p>
- */
+
 public class DownloadWorker implements Runnable {
 
     private final ChunkStatus chunkStatus;
@@ -21,23 +15,51 @@ public class DownloadWorker implements Runnable {
 
     @Override
     public void run() {
-        // 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("[" + Thread.currentThread().getName() + "] Started downloading Chunk #" +
+                chunkStatus.getChunkId() + " (Size: " + chunkStatus.getChunkSizeMB() + " MB)");
 
         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 minDelay = config.getMinStepDelayMs();
+            int maxDelay = config.getMaxStepDelayMs();
+            int delay = minDelay + random.nextInt(maxDelay - minDelay + 1);
+
+            try {
+                Thread.sleep(delay);
+            } catch (InterruptedException e) {
+                System.out.println("[" + Thread.currentThread().getName() + "] Chunk #" +
+                        chunkStatus.getChunkId() + " was interrupted!");
+                Thread.currentThread().interrupt();
+                break;
             }
 
-        // TODO: Mark the chunk as completed.
-        // TODO: Record the chunk end time in chunkStatus.
-        // TODO: Print a message that this chunk has finished downloading.
+            double minStep = config.getMinStepDownloadMB();
+            double maxStep = config.getMaxStepDownloadMB();
+            double stepDownload = minStep + (random.nextDouble() * (maxStep - minStep));
+
+            downloaded += stepDownload;
+            if (downloaded > chunkStatus.getChunkSizeMB()) {
+                downloaded = chunkStatus.getChunkSizeMB();
             }
 
+            chunkStatus.setDownloadedMB(downloaded);
+
+            System.out.printf("[%s] Chunk #%d progress: %.2f/%.1f MB (%.1f%%)%n",
+                    Thread.currentThread().getName(),
+                    chunkStatus.getChunkId(),
+                    downloaded,
+                    chunkStatus.getChunkSizeMB(),
+                    chunkStatus.getProgressPercentage()
+            );
+        }
+
+        chunkStatus.setCompleted(true);
+        chunkStatus.setEndTimeMs(System.currentTimeMillis());
+
+        long totalTime = chunkStatus.getDownloadDurationMs();
+        System.out.println("[" + Thread.currentThread().getName() + "] Finished Chunk #" +
+                chunkStatus.getChunkId() + " in " + totalTime + " ms!");
+    }
 }

src/main/java/Main.java

@@ -5,7 +5,6 @@ public class Main {
     public static void main(String[] args) {
         System.out.println("=== Simulated Download Manager ===");
 
-        // 1. Read config
         DownloadConfig config;
         try {
             config = ConfigReader.readConfig("download_config.txt");
@@ -19,13 +18,11 @@ public class Main {
         System.out.println("Chunk count: " + config.getChunkCount());
         System.out.println();
 
-        // 2. Create chunks
         List<ChunkStatus> chunks = ChunkUtils.createChunks(
                 config.getTotalSizeMB(),
                 config.getChunkCount()
         );
 
-        // 3. Create worker threads
         List<Thread> workerThreads = new ArrayList<>();
 
         for (ChunkStatus chunk : chunks) {
@@ -34,50 +31,30 @@ public class Main {
 
             workerThreads.add(workerThread);
 
-            // TODO:
-            // Students may print helpful debug information here,
-            // for example which chunk is assigned to which worker thread.
+            System.out.println("[Setup] Created " + workerThread.getName() + " for Chunk #" +
+                    chunk.getChunkId() + " (Size: " + chunk.getChunkSizeMB() + " MB)");
         }
 
-        // 4. Create and start monitor thread
         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.
+        for (Thread thread : workerThreads) {
+            thread.start();
+        }
 
-        // 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.
+        try {
+            for (Thread thread : workerThreads) {
+                thread.join();
+            }
+            monitorThread.join();
+        } catch (InterruptedException e) {
+            System.out.println("[Main] Error: The main monitor thread was interrupted.");
+            Thread.currentThread().interrupt();
+        }
 
-        // NOTE:
-        // this final report may show 0 progress because no worker has actually run yet.
-        // Until students complete the thread start/join TODOs above,
-
-        // 7. Print final report
         System.out.println();
         System.out.println("=== Final Report ===");
 
@@ -101,7 +78,7 @@ public class Main {
 
         System.out.println();
         System.out.println("Completed chunks: " + completedChunks + "/" + chunks.size());
-        System.out.println("Downloaded total: " + downloadedMB + "/" + config.getTotalSizeMB() + " MB");
+        System.out.println("Total downloaded: " + downloadedMB + "/" + config.getTotalSizeMB() + " MB");
         System.out.println("Simulation finished.");
     }
 }

src/main/java/ProgressMonitor.java

@@ -16,16 +16,6 @@ public class ProgressMonitor implements Runnable {
 
     @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
-
 
         while (true) {
             double totalDownloadedMB = 0.0;
@@ -54,14 +44,16 @@ public class ProgressMonitor implements Runnable {
                     chunks.size()
             );
 
-
-            // TODO:
-            // If all chunks are completed, print a final message and exit the loop
+            if (completedChunks == chunks.size()) {
+                System.out.printf("[Monitor] Download complete for %s! Total size: %d MB.%n", fileName, totalSizeMB);
+                break;
+            }
 
             try {
                 Thread.sleep(monitorDelayMs);
             } catch (InterruptedException e) {
                 System.out.println("Progress monitor interrupted.");
+                Thread.currentThread().interrupt();
                 return;
             }
         }