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();    
    }  
}  

Questions:

• What output do you get from the program? Why?

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

---

Answers:

1 : t1.run() executes the run() method directly in the main thread, printing "Running in: main". t2.start() creates a new thread (Thread-2) that executes the run() method, printing "Running in: Thread-2". Thread.sleep(100) ensures t1’s output appears before t2’s, though Thread-2’s output timing depends on JVM scheduling.

Output:

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

2 : run() is a regular method call in the current thread; start() initiates a new thread for concurrent execution.

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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.");    
    }  
}  

Questions:

• What output do you get from the program? Why?

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

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

---

Answers:

1 : Output: "Main thread ends." followed by a few (or none) "Daemon thread running..." messages.

Main thread ends.
Daemon thread running...

The thread is a daemon thread, so the JVM exits when the main thread ends, terminating the daemon thread early, even though its loop (20 iterations) hasn’t completed.

2 : Output: "Main thread ends." followed by "Daemon thread running..." printed 20 times over ~10 seconds.

Without setDaemon(true), the thread is a user thread, so the JVM waits for it to finish all 20 iterations before exiting.

3 : Garbage collection, logging, IDE background tasks, etc.

They handle non-critical background tasks that automatically stop when the main application ends, avoiding manual cleanup.

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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();  
    }  
}   

Questions:

• What output do you get from the program?

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

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

---

Answers:

1 : Thread is running using a ...!

2 : It’s called a lambda expression.

3 :

• Lambda: Short and inline, good for simple tasks, but not reusable.
• Implements Runnable: More code, reusable, better for complex tasks.
• Extends Thread: More code, less flexible due to inheritance, not usually recommended.