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

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

Report.md

@@ -0,0 +1,57 @@
+## Theoretical Questions
+### 1. `start()` vs `run()`
+- What output do you get from the program? Why?
+    ```
+    Calling run()
+    Running in: main
+    Calling start()
+    Running in: Thread-2
+    ```
+    → When `t1.run()` is called directly, we're calling the `run()` method like a 
+normal method and no new thread is created. The `run()` method is executed on the 
+current thread (main); so `Thread.currentThread().getName()` returns "main".
+<br/> When `t2.start()` is called: `start()` creates a new thread named "Thread-2".
+The new thread automatically calls  `run()` so `Thread.currentThread().getName()` returns "Thread-2".
+
+- What’s the difference in behavior between calling `start()` and `run()`?
+→ `start()`: creates a new thread and is executed on a new thread.
+  `run()`: method doesn't create new thread and is executed on the current thread.
+
+### 2. Daemon Threads
+
+- What output do you get from the program? Why?
+    ```
+    Main thread ends.
+    Daemon thread running...
+    ```
+    → The thread is set as a Daemon thread. The main thread ends immediately after
+printing "Main thread ends." and the JVM exits without waiting for the daemon thread to complete its loop.
+
+- What happens if you remove `thread.setDaemon(true)`?
+
+  → The thread becomes a user thread. The main thread still ends,
+but the JVM will not exit because there is still a live user thread. 
+The program will print all 20 "Daemon thread running..." messages.
+- What are some real-life use cases of daemon threads?
+
+    → Spell Checker / Grammar Checker in Word.
+
+### 3. A shorter way to create threads
+
+- What output do you get from the program?
+    ```
+    Thread is running using a ...!
+    ```
+- What is the `() -> { ... }` syntax called?
+
+    → lambda expression
+
+- How is this code different from creating a class that extends `Thread` or implements `Runnable`?
+  
+    → The code uses a lambda expression to define the `run()` method inline. 
+When you extend `Thread`, you must create a separate subclass, override the `run()` method,
+and then instantiate that subclass. This gives you the ability to add 
+new fields or methods to your thread class, but it also means you cannot extend any other class.
+When you implement `Runnable` using an anonymous class (the old way before lambdas), you write:
+
+    `new Runnable() { public void run() { ... } }`.

src/main/java/DownloadWorker.java

@@ -1,3 +1,4 @@
+import java.sql.SQLOutput;
 import java.util.Random;
 
 /**
@@ -21,23 +22,42 @@ 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.printf("worker-%d starting download of chunk (size: %.2f MB)%n", chunkStatus.getChunkId(), chunkStatus.getChunkSizeMB());
 
         while (downloaded < chunkStatus.getChunkSizeMB()) {
-            // TODO: Generate a random sleep delay between min and max delay.
+            int delay = config.getMinStepDelayMs() + random.nextInt(config.getMaxStepDelayMs()-config.getMinStepDelayMs()+1);
-            // TODO: Sleep for that delay.
+            try
-            // TODO: Generate a random download amount for this step.
+            {
-            // TODO: Increase downloaded, but do not go beyond chunk size.
+                Thread.sleep(delay);
-            // TODO: Save the updated downloaded value into chunkStatus.
+            } catch (InterruptedException e)
-            // TODO: Optionally print step-by-step progress.
+            {
+                Thread.currentThread().interrupt();
+                System.err.printf("worker-%d interrupted%n", chunkStatus.getChunkId());
+                break;
+            }
+
+            double stepSize = config.getMinStepDownloadMB() + random.nextDouble() * (config.getMaxStepDownloadMB() - config.getMinStepDownloadMB());
+            downloaded += stepSize;
+            if (downloaded > chunkStatus.getChunkSizeMB())
+            {
+                downloaded = chunkStatus.getChunkSizeMB();
+            }
+            chunkStatus.setDownloadedMB(downloaded);
+
+            System.out.printf("worker-%d progress: %.2f / %.2f MB (%.1f%%)%n",
+                    chunkStatus.getChunkId(),
+                    downloaded,
+                    chunkStatus.getChunkSizeMB(),
+                    (downloaded / chunkStatus.getChunkSizeMB()) * 100);
         }
 
-        // TODO: Mark the chunk as completed.
+        chunkStatus.setCompleted(true);
-        // TODO: Record the chunk end time in chunkStatus.
+        chunkStatus.setEndTimeMs(System.currentTimeMillis());
-        // TODO: Print a message that this chunk has finished downloading.
+        System.out.printf("worker-%d chunk download completed. Time: %d ms%n",
-    }
+                chunkStatus.getChunkId(),
+                chunkStatus.getDownloadDurationMs());    }
 
 }

src/main/java/Main.java

@@ -34,48 +34,37 @@ public class Main {
 
             workerThreads.add(workerThread);
 
-            // TODO:
+            System.out.println("Created worker thread: " + workerThread.getName() +
-            // Students may print helpful debug information here,
+                    " for chunk #" + chunk.getChunkId() +
-            // for example which chunk is assigned to which worker thread.
+                    " (size: " + chunk.getChunkSizeMB() + " MB)");
         }
 
         // 4. Create and start monitor thread
         ProgressMonitor monitor = new ProgressMonitor(config, chunks);
         Thread monitorThread = new Thread(monitor, "Progress-Monitor");
 
-        // TODO:
+        monitorThread.start();
-        // Start the monitor thread before starting the workers
+        System.out.println("monitor thread started.");
-        // so that progress can be displayed while downloading happens.
-        //
-        // Example idea:
-        // monitorThread.start();
 
-        // 5. Start worker threads
+        for (Thread thread : workerThreads)
-        // TODO:
+        {
-        // Start each worker thread in workerThreads.
+            thread.start();
-        // Use a loop and call start() on each thread.
+            System.out.println("started: "+thread.getName());
+        }
 
-        // 6. Wait for workers to finish
+        try
-        // TODO:
+        {
-        // Wait for all worker threads to complete by calling join().
+            for (Thread thread : workerThreads)
-        // This should be done inside a try-catch block for InterruptedException.
+            {
-        //
+                thread.join();
-        // Hint:
-        // for (Thread thread : workerThreads) {
-        //     thread.join();
-        // }
 
-        // TODO:
+            }
-        // After all workers finish, the monitor thread may also need to stop.
+        } catch (InterruptedException e)
-        // Depending on how ProgressMonitor is implemented, students may:
+        {
-        // - wait for it to finish on its own, or
+            System.out.println("main thread interrupted while waiting for workers.");
-        // - add a stopping mechanism in ProgressMonitor later.
+            Thread.currentThread().interrupt();
-        //
+            return;
-        // 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,
 
         // 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 +45,11 @@ public class ProgressMonitor implements Runnable {
             );
 
 
-            // TODO:
+            if (completedChunks == chunks.size())
-            // If all chunks are completed, print a final message and exit the loop
+            {
+                System.out.printf("All chunks completed for %s. Monitor stopping>%n", fileName);
+                break;
+            }
 
             try {
                 Thread.sleep(monitorDelayMs);