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

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This commit was merged in pull request #1.
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HoseinA05
2026-07-03 07:52:01 +00:00
parent 9e5c715088 dc9839c911
commit 4e224bc8b3
5 changed files with 127 additions and 75 deletions
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.idea/misc.xml
Generated
+1 -1
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@@ -8,7 +8,7 @@
</list>
</option>
</component>
<component name="ProjectRootManager" version="2" languageLevel="JDK_21" default="true" project-jdk-name="21" project-jdk-type="JavaSDK">
<component name="ProjectRootManager" version="2" languageLevel="JDK_25" default="true" project-jdk-name="25" project-jdk-type="JavaSDK">
<output url="file://$PROJECT_DIR$/out" />
</component>
</project>
Report.md
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@@ -0,0 +1,63 @@
## Answers to Theoretical Questions
### 1. `start()` vs `run()`
**Output:**
```
Calling run()
Running in: main
Calling start()
Running in: Thread-2
```
- When we call `run()` directly, it's just a normal method call.
No new thread is created – everything happens inside the current thread (here `main`).
That's why the printed thread name is `main`.
- Calling `start()` actually creates a brand new thread and then runs `run()` inside that new thread.
So the output shows that `Thread-2` is the one executing the code.
- The main difference:
`run()` → synchronous, runs in the caller thread.
`start()` → asynchronous, spawns a separate thread and runs `run()` there.
---
### 2. Daemon Threads
**Program output (when `setDaemon(true)` is used):**
```
Main thread ends.
Daemon thread running...
```
(Only a few lines might appear before the program exits.)
- By marking the thread as a daemon, we tell the JVM: *"This thread is doing background work – don't wait for it."*
As soon as all **user threads** finish, the JVM shuts down, even if daemon threads are still running.
Here `main` is a user thread, so after it prints its message and ends, the program terminates quickly.
- If we **remove** `thread.setDaemon(true)`, the thread becomes a normal user thread.
Then the JVM will wait for it to finish all 20 iterations before exiting.
We'd see `"Daemon thread running..."` printed 20 times.
- Real‑life examples of daemon threads:
- The **garbage collector** in Java – runs in the background but won't stop the JVM from closing.
- **Auto‑save** in a text editor – saves periodically but shouldn't block the program from closing.
---
### 3. A shorter way to create threads
**Output:**
```
Thread is running using a ...!
```
- The `() -> { ... }` part is a **lambda expression**.
It's a compact way to write an anonymous function.
- Instead of creating a whole new class that implements `Runnable` (or extending `Thread`), we can just pass the body of `run()` directly inside `new Thread(...)`.
This makes the code much shorter and easier to read, especially for one‑off tasks.
- Lambdas are perfect for simple jobs, but if the task is complex or needs to be reused, a separate class might be better.
src/main/java/DownloadWorker.java
+19 -20
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@@ -1,12 +1,5 @@
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 +14,29 @@ public class DownloadWorker implements Runnable {
@Override
public void run() {
// TODO: Record the chunk start time in chunkStatus.
chunkStatus.setStartTimeMs(System.currentTimeMillis());
System.out.println("Chunk " + chunkStatus.getChunkId() + " started downloading.");
double downloaded = 0.0;
double chunkSize = chunkStatus.getChunkSizeMB();
// TODO: Print a message that this chunk has started downloading.
while (downloaded < chunkSize) {
int delay = config.getMinStepDelayMs()
+ random.nextInt(config.getMaxStepDelayMs() - config.getMinStepDelayMs() + 1);
try {
Thread.sleep(delay);
}
catch (InterruptedException e) {
break;
}
double step = config.getMinStepDownloadMB()
+ random.nextDouble() * (config.getMaxStepDownloadMB() - config.getMinStepDownloadMB());
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.
downloaded = Math.min(downloaded + step, chunkSize);
chunkStatus.setDownloadedMB(downloaded);
}
// 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("Chunk " + chunkStatus.getChunkId() + " finished downloading.");
}
}
src/main/java/Main.java
+19 -39
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@@ -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");
@@ -18,14 +17,13 @@ public class Main {
System.out.println("Total size (MB): " + config.getTotalSizeMB());
System.out.println("Chunk count: " + config.getChunkCount());
System.out.println();
System.out.println("Starting download...\n");
// 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) {
@@ -33,51 +31,32 @@ public class Main {
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: Worker-" + chunk.getChunkId() + " -> Chunk " + chunk.getChunkId());
}
// 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 thread 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.
try {
monitorThread.join();
} catch (InterruptedException e) {
System.out.println("Main thread interrupted while waiting for monitor.");
}
// 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 ===");
@@ -103,5 +82,6 @@ public class Main {
System.out.println("Completed chunks: " + completedChunks + "/" + chunks.size());
System.out.println("Downloaded total: " + downloadedMB + "/" + config.getTotalSizeMB() + " MB");
System.out.println("Simulation finished.");
System.out.println("Thank you for using the download manager!");
}
}
src/main/java/ProgressMonitor.java
+25 -15
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@@ -6,26 +6,19 @@ public class ProgressMonitor implements Runnable {
private final int totalSizeMB;
private final List<ChunkStatus> chunks;
private final long monitorDelayMs;
private final long startTimeMs;
public ProgressMonitor(DownloadConfig config, List<ChunkStatus> chunks) {
this.fileName = config.getFileName();
this.totalSizeMB = config.getTotalSizeMB();
this.chunks = chunks;
this.monitorDelayMs = 500;
this.startTimeMs = System.currentTimeMillis();
}
@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
System.out.println("=== Download Progress ===");
while (true) {
double totalDownloadedMB = 0.0;
@@ -44,19 +37,36 @@ public class ProgressMonitor implements Runnable {
percent = (totalDownloadedMB * 100.0) / totalSizeMB;
}
System.out.printf(
"Progress for %s: %.1f/%.1f MB (%.2f%%), completed chunks: %d/%d%n",
long elapsedMs = System.currentTimeMillis() - startTimeMs;
double elapsedSec = elapsedMs / 1000.0;
double speedMBps = (elapsedSec > 0) ? (totalDownloadedMB / elapsedSec) : 0.0;
double remainingMB = totalSizeMB - totalDownloadedMB;
double etaSec = (speedMBps > 0) ? (remainingMB / speedMBps) : 0.0;
int barLength = 30;
int filled = (int) (percent / 100.0 * barLength);
StringBuilder bar = new StringBuilder("[");
for (int i = 0; i < barLength; i++) {
bar.append(i < filled ? "=" : " ");
}
bar.append("]");
System.out.printf("\r%s %s %.1f/%.1f MB (%.1f%%) | Speed: %.1f MB/s | ETA: %.0fs | Chunks: %d/%d",
bar.toString(),
fileName,
totalDownloadedMB,
(double) totalSizeMB,
percent,
speedMBps,
etaSec,
completedChunks,
chunks.size()
);
// TODO:
// If all chunks are completed, print a final message and exit the loop
if (completedChunks == chunks.size()) {
System.out.println("Monitor: All chunks completed.");
break;
}
try {
Thread.sleep(monitorDelayMs);