Assignment-8/Report.md

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();    
    }  
}

What output do you get from the program? Why?

• The output is:

Calling run()
Running in: main
Calling start()
Running in: Thread-2

Since t1.run() executes the run() method directly inside the main thread, but t2.start() executes it inside the created new thread.

What’s the difference in behavior between calling start() and run()?

• Calling run() is just a normal method call, so the program waits for it to finish before moving to the next line.

  Calling start() tells Java to create a new thread and execute the run() method inside it, which allows it to run alongside the main thread.

---

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.");    
    }  
}

What output do you get from the program? Why?

• The output is:

Main thread ends.
Daemon thread running...

Since thread.setDaemon(true) marks the thread as a background "daemon" thread, the program ends as soon as all user (non-daemon) threads (the main thread in this case) have finished, regardless of whether the daemon thread has completed its task.

What happens if you remove thread.setDaemon(true)?

• The program continues printing Daemon thread running... 20 times even after the main thread has finished.

Main thread ends.
Daemon thread running...
.
.
.
Daemon thread running...

What are some real-life use cases of daemon threads?

• In general, when we want a background task to run only while the main program is running, we use daemon threads.

  For example, background tasks like cache clearing, checking connectivity to a server, or monitoring CPU/Memory usage can all be done using daemon threads.

---

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();  
    }  
}

What output do you get from the program?

• The output is:

Thread is running using a ...!

What is the () -> { ... } syntax called?

• It's called a lambda expression

How is this code different from creating a class that extends Thread or implements Runnable?

• It’s much shorter and easier to read. Instead of having to define a new custom thread class (by extending Thread) or separate the task from the thread itself (by implementing Runnable) just to run a few lines of code, a lambda expression lets us pass the code directly to the thread.