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Added REPORT.md for the theoretical questions

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Finished ProgressMonitor, DownloadWorker and Main classes.
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farnam_jhn
2026-06-02 14:17:00 +03:30
parent 9e5c715088
commit 5eb6343ba6
4 changed files with 140 additions and 64 deletions
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REPORT.md
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## Q1
```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();
}
}
```
### Answer
#### Output
the program first outputs `Calling run()`
then it runs the `t1` by calling the `run` method in the `t1` thread
t1's run method outputs `Running in: Thread-1`
the program waits 100ms (`Thread.sleep(100)`) after that a new thread is created called `t2`
the program outputs `Calling start()` and then `Running in: Thread-2`
#### Difference between `run()` and `start()`
when we call `t1.run()` the program stops at this line, no new thread would be created and run method runs on the main thread
but when we call `t2.start()` a new thread would get created and main thread runs alongside the new thread.
## Q2
```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.");
}
}
```
### Answer
#### Output
The program creates a thread from DaemonRunnable class, after that it sets to a be a daemon output first message: `Daemon thread running...` and just as it's in sleep (`Thread.sleep(500)`) the main thread finishes its job
and outputs: `Main thread ends.`. this would end the daemon thread we started.
#### What if we removed `thread.setDaemon(true)`
if we removed this line `thread` would've been a normal thread, meaning when we reach the end of the main thread `thread` would still continue doing its work (which is printing `Daemon thread running...`)
The Main thread would've waited for `thread` to finish its job before ending the program.
#### Real life use cases
`sshd` is a daemon that listens for any SSH connections to the computer
another example would be `systemd` which is a daemon on most of the linux distros that manages services
## Q3
```java
public class ThreadDemo {
public static void main(String[] args) {
Thread thread = new Thread(() -> {
System.out.println("Thread is running using a ...!");
});
thread.start();
}
}
```
### Answer
#### Output
the program simply just outputs `Thread is running using a ...!`
#### What is the `() -> {...}` syntax called
`() -> {...}` is a lambda expression with no parameters: `()`
#### Difference between this and a normal class
using this lambda expression we don't need to create another class
src/main/java/DownloadWorker.java
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import java.time.LocalTime;
import java.util.Random;
import java.lang.Thread;
/**
* Simulates downloading a single chunk of a file.
@@ -21,23 +23,33 @@ public class DownloadWorker implements Runnable {
@Override
public void run() {
// TODO: Record the chunk start time in chunkStatus.
// Records current system time
chunkStatus.setStartTimeMs(System.currentTimeMillis());
double downloaded = 0.0;
// TODO: Print a message that this chunk has started downloading.
System.out.println("A new chunk downloader with id: " + chunkStatus.getChunkId() + " started downloading...");
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.
// Sleeps the thread to mimic a part of the chunk being downloaded in the random time.
try{
Thread.sleep(random.nextInt(5000));
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
// Gets a random number as the downloaded size in the random timespan
double downloadedSizeMB = random.nextDouble(chunkStatus.getChunkSizeMB());
downloaded += downloadedSizeMB;
chunkStatus.setDownloadedMB(downloaded);
System.out.println("Downloaded: " + downloadedSizeMB + "MBs.");
}
// TODO: Mark the chunk as completed.
// TODO: Record the chunk end time in chunkStatus.
// TODO: Print a message that this chunk has finished downloading.
// Sets the chunk status, records the end time
chunkStatus.setCompleted(true);
chunkStatus.setEndTimeMs(System.currentTimeMillis());
System.out.println("Chunk downloader with id: " + chunkStatus.getChunkId() + " finished its work.");
}
}
src/main/java/Main.java
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workerThreads.add(workerThread);
// TODO:
// Students may print helpful debug information here,
// for example which chunk is assigned to which worker thread.
System.out.println("Chunk with id: " + chunk.getChunkId() + " is assigned to Thread: " + workerThread.getName());
}
// 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();
// 5. Start worker threads & monitor thread
// 5. Start worker threads
// TODO:
// Start each worker thread in workerThreads.
// Use a loop and call start() on each thread.
monitorThread.start();
for (Thread workerThread : workerThreads){
workerThread.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();
// }
// 6. Wait for the workers to finish
for (Thread workerThread : workerThreads){
try {
workerThread.join();
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}
// 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) {
throw new RuntimeException(e);
}
// 7. Print final report
System.out.println();
src/main/java/ProgressMonitor.java
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@@ -16,17 +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;
int completedChunks = 0;
@@ -54,15 +43,18 @@ public class ProgressMonitor implements Runnable {
chunks.size()
);
// TODO:
// If all chunks are completed, print a final message and exit the loop
try {
Thread.sleep(monitorDelayMs);
} catch (InterruptedException e) {
System.out.println("Progress monitor interrupted.");
return;
if (completedChunks == chunks.size()){
System.out.println("All workers finished their job, downloaded the file successfully. \nHere's the report: ");
for (ChunkStatus chunk : chunks){
System.out.println(chunk.toString());
}
break;
}else {
try {
Thread.sleep(monitorDelayMs);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}
}
}