Merge pull request 'tamrin 8' (#1) from develop into main

Reviewed-on: navid299/HW-08-Basic-Multithreading#1

Report.md

@@ -0,0 +1,124 @@
+## 1 . `start()` vs `run()` :
+
+```
+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();    
+    }  
+}  
+```
+### Questions and Answers:  
+* **What output do you get from the program? Why?**
+    * ```
+      //output:
+      Calling run()
+      Running in : main
+      Calling start()
+      Running in : Thread-2
+      ```
+    *  *When `t1.run()` is called directly, it executes the `run()` method in the current thread (the main thread), just like a normal method call. No new thread is created. Therefore, `Thread.currentThread().getName()` returns `"main"`.*  
+    <br>
+    * *When `t2.start()` is called, it creates a new thread named `"Thread-2"` and the JVM automatically invokes the `run()` method inside that new thread. Hence, `Thread.currentThread().getName()` returns `"Thread-2"`.*  
+    <br> 
+* **What’s the difference in behavior between calling `start()` and `run()`?**  
+    <br>
+    * *Calling `run()` directly just executes the code inside `run()` in the caller's thread – it's not multithreading.*  
+    <br>
+    * *Calling `start()` schedules the thread to run, and the `run()` method will be executed in a separate thread concurrently.*
+
+***
+
+## 2. Daemon Threads :
+```
+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.");    
+    }  
+}  
+```
+### Questions and Answers:  
+
+* **What output do you get from the program? Why?**  
+   * ```
+     //output:
+     Main thread ends.
+     Daemon thread running...
+     Daemon thread running...
+     ...
+     //(less than 20 times)
+      ```
+   * *The main thread prints `"Main thread ends."` and then terminates.*  
+   <br> 
+   * *The other thread is a `daemon thread`. Daemon threads are background threads that do not prevent the JVM from exiting.*  
+   <br>
+   * *When the last non-daemon thread (in this case, only the main thread) finishes, the JVM terminates immediately without waiting for the daemon thread to complete its loop.*  
+   <br>
+   * *Therefore, the daemon thread only gets to print a few lines before the program shuts down. It never reaches 20 iterations.*  
+   <br>  
+* **What happens if you remove thread.setDaemon(true)?**  
+    <br>
+    * *The thread prints 20 times and then the program ends, because the thread is no longer a daemon (it becomes a regular user thread).*
+*  **What are some real-life use cases of daemon threads?**  
+    <br>
+     1. *Background music in a game – While you play, music plays in the background. When you close the game, the music stops immediately. No need to finish the song.*  
+     <br>
+     2. *Auto-save in a text editor – Every few minutes, the program saves your file automatically. If you close the program, it doesn't matter if the auto-save finishes or not. Just stop.*  
+<br>
+
+***
+
+## 3. A shorter way to create threads :  
+```
+public class ThreadDemo {  
+    public static void main(String[] args) {  
+        Thread thread = new Thread(() -> {  
+            System.out.println("Thread is running using a ...!");  
+        });  
+  
+        thread.start();  
+    }  
+}   
+```
+### Questions and Answers:  
+
+* **What output do you get from the program?**  
+  * ```
+    //output:
+    Thread is running using a ...!
+    ```
+* **What is the `() -> { ... }` syntax called?**    
+ <br>
+    * *It is called a Lambda Expression*  
+ <br>
+* **How is this code different from creating a class that extends `Thread` or implements `Runnable`?**  
+ <br>
+   * *Shorter and cleaner code.*
+   * *No need for a separate class or explicit `run()` override.*
+   * *Lambda directly provides the `run()` body.*

src/main/java/DownloadWorker.java

@@ -21,23 +21,48 @@ 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() + " (" + 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 delayMs = config.getMinStepDelayMs() +
+                    random.nextInt(config.getMaxStepDelayMs() - config.getMinStepDelayMs() + 1);
+            try {
+                Thread.sleep(delayMs);
+            } catch (InterruptedException e) {
+                System.out.println(Thread.currentThread().getName() + " interrupted");
+                return;
+            }
+
+            // Generate random download amount for this step
+            double step = config.getMinStepDownloadMB() +
+                    random.nextDouble() * (config.getMaxStepDownloadMB() - config.getMinStepDownloadMB());
+            downloaded += step;
+            if (downloaded > chunkStatus.getChunkSizeMB()) {
+                downloaded = chunkStatus.getChunkSizeMB();
+            }
+
+            // Update shared status
+            chunkStatus.setDownloadedMB(downloaded);
+
+            // Optional step progress print
+            System.out.printf("%s: chunk %d -> %.2f / %.2f MB (%.1f%%)%n",
+                    Thread.currentThread().getName(),
+                    chunkStatus.getChunkId(),
+                    downloaded,
+                    chunkStatus.getChunkSizeMB(),
+                    (downloaded / chunkStatus.getChunkSizeMB()) * 100);
         }
 
-        // 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());
+
+        System.out.println(Thread.currentThread().getName() + " FINISHED chunk " +
+                chunkStatus.getChunkId() + " in " +
+                (chunkStatus.getEndTimeMs() - chunkStatus.getStartTimeMs()) + " ms");
     }
 
 }

src/main/java/Main.java

@@ -34,48 +34,35 @@ 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("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 t : workerThreads) {
+            t.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();
-        // }
+        for (Thread t : workerThreads) {
+            try {
+                t.join();
+            } catch (InterruptedException e) {
+                System.out.println("Main interrupted while waiting for workers.");
+            }
+        }
 
-        // 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,
+        try {
+            monitorThread.join();
+        } catch (InterruptedException e) {
+            System.out.println("Main interrupted while waiting for monitor.");
+        }
 
         // 7. Print final report
         System.out.println();

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;
@@ -55,8 +45,10 @@ public class ProgressMonitor implements Runnable {
             );
 
 
-            // TODO:
-            // If all chunks are completed, print a final message and exit the loop
+            if (completedChunks == chunks.size()) {
+                System.out.println("All chunks completed. Monitor thread stopping.");
+                break;
+            }
 
             try {
                 Thread.sleep(monitorDelayMs);

src/main/resources/download_config.txt

@@ -1,7 +1,7 @@
-fileName=movie.mkv
-totalSizeMB=120
-chunkCount=6
-minStepDelayMs=80
-maxStepDelayMs=200
-minStepDownloadMB=2
-maxStepDownloadMB=6
+    fileName=movie.mkv
+    totalSizeMB=120
+    chunkCount=6
+    minStepDelayMs=80
+    maxStepDelayMs=200
+    minStepDownloadMB=2
+    maxStepDownloadMB=6