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Implement download manager

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saeedjamali
2026-06-05 18:39:25 +03:30
parent 9e5c715088
commit 960cbcb7cb
3 changed files with 50 additions and 90 deletions
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src/main/java/DownloadWorker.java
+24 -20
View File
@@ -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 +14,34 @@ 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("[Worker-" + chunkStatus.getChunkId() + "] Started downloading chunk of size: " + String.format("%.2f", 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.
try {
int delay = config.getMinStepDelayMs() + random.nextInt(config.getMaxStepDelayMs() - config.getMinStepDelayMs() + 1);
Thread.sleep(delay);
double stepDownload = config.getMinStepDownloadMB() + (random.nextDouble() * (config.getMaxStepDownloadMB() - config.getMinStepDownloadMB()));
downloaded += stepDownload;
if (downloaded > chunkStatus.getChunkSizeMB()) {
downloaded = chunkStatus.getChunkSizeMB();
}
chunkStatus.setDownloadedMB(downloaded);
} catch (InterruptedException e) {
System.err.println("Worker-" + chunkStatus.getChunkId() + " was interrupted.");
return;
}
}
// 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("[Worker-" + chunkStatus.getChunkId() + "] Finished downloading.");
}
}
src/main/java/Main.java
+20 -50
View File
@@ -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");
@@ -19,65 +18,38 @@ 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) {
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() + " to " + workerThread.getName());
}
// 4. Create and start monitor thread
ProgressMonitor monitor = new ProgressMonitor(config, chunks);
Thread monitorThread = new Thread(monitor, "Progress-Monitor");
monitorThread.start();
// TODO:
// Start the monitor thread before starting the workers
// so that progress can be displayed while downloading happens.
//
// Example idea:
// monitorThread.start();
for (Thread thread : workerThreads) {
thread.start();
}
// 5. Start worker threads
// TODO:
// Start each worker thread in workerThreads.
// Use a loop and call start() on each thread.
try {
for (Thread thread : workerThreads) {
thread.join();
}
monitorThread.join();
} catch (InterruptedException e) {
System.err.println("Main thread interrupted while waiting for workers.");
}
// 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.
// 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 ===");
@@ -86,22 +58,20 @@ public class Main {
for (ChunkStatus chunk : chunks) {
downloadedMB += chunk.getDownloadedMB();
if (chunk.isCompleted()) {
completedChunks++;
}
System.out.println(
"Chunk " + chunk.getChunkId()
+ ": " + chunk.getDownloadedMB()
+ "/" + chunk.getChunkSizeMB()
+ " MB"
);
System.out.printf("Chunk %d: %.2f/%.2f MB (Duration: %d ms)%n",
chunk.getChunkId(),
chunk.getDownloadedMB(),
chunk.getChunkSizeMB(),
chunk.getDownloadDurationMs());
}
System.out.println();
System.out.println("Completed chunks: " + completedChunks + "/" + chunks.size());
System.out.println("Downloaded total: " + downloadedMB + "/" + config.getTotalSizeMB() + " MB");
System.out.printf("Downloaded total: %.2f/%d MB%n", downloadedMB, config.getTotalSizeMB());
System.out.println("Simulation finished.");
}
}
}
src/main/java/ProgressMonitor.java
+6 -20
View File
@@ -16,33 +16,18 @@ 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;
int completedChunks = 0;
for (ChunkStatus chunk : chunks) {
totalDownloadedMB += chunk.getDownloadedMB();
if (chunk.isCompleted()) {
completedChunks++;
}
}
double percent = 0.0;
if (totalSizeMB > 0) {
percent = (totalDownloadedMB * 100.0) / totalSizeMB;
}
double percent = (totalSizeMB > 0) ? (totalDownloadedMB * 100.0) / totalSizeMB : 100.0;
System.out.printf(
"Progress for %s: %.1f/%.1f MB (%.2f%%), completed chunks: %d/%d%n",
@@ -54,9 +39,10 @@ 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.println("Monitor: All chunks completed. Shutting down monitor...");
break;
}
try {
Thread.sleep(monitorDelayMs);
@@ -66,4 +52,4 @@ public class ProgressMonitor implements Runnable {
}
}
}
}
}