## 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 and Answers:  
* **What output do you get from the program? Why?**
    * ```
      //output:
      Calling run()
      Running in : main
      Calling start()
      Running in : Thread-2
      ```
    *  *When `t1.run()` is called directly, it executes the `run()` method in the current thread (the main thread), just like a normal method call. No new thread is created. Therefore, `Thread.currentThread().getName()` returns `"main"`.*  
    <br>
    * *When `t2.start()` is called, it creates a new thread named `"Thread-2"` and the JVM automatically invokes the `run()` method inside that new thread. Hence, `Thread.currentThread().getName()` returns `"Thread-2"`.*  
    <br> 
* **What’s the difference in behavior between calling `start()` and `run()`?**  
    <br>
    * *Calling `run()` directly just executes the code inside `run()` in the caller's thread – it's not multithreading.*  
    <br>
    * *Calling `start()` schedules the thread to run, and the `run()` method will be executed in a separate thread concurrently.*

***

## 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 and Answers:  

* **What output do you get from the program? Why?**  
   * ```
     //output:
     Main thread ends.
     Daemon thread running...
     Daemon thread running...
     ...
     //(less than 20 times)
      ```
   * *The main thread prints `"Main thread ends."` and then terminates.*  
   <br> 
   * *The other thread is a `daemon thread`. Daemon threads are background threads that do not prevent the JVM from exiting.*  
   <br>
   * *When the last non-daemon thread (in this case, only the main thread) finishes, the JVM terminates immediately without waiting for the daemon thread to complete its loop.*  
   <br>
   * *Therefore, the daemon thread only gets to print a few lines before the program shuts down. It never reaches 20 iterations.*  
   <br>  
* **What happens if you remove thread.setDaemon(true)?**  
    <br>
    * *The thread prints 20 times and then the program ends, because the thread is no longer a daemon (it becomes a regular user thread).*
*  **What are some real-life use cases of daemon threads?**  
    <br>
     1. *Background music in a game – While you play, music plays in the background. When you close the game, the music stops immediately. No need to finish the song.*  
     <br>
     2. *Auto-save in a text editor – Every few minutes, the program saves your file automatically. If you close the program, it doesn't matter if the auto-save finishes or not. Just stop.*  
<br>

***

## 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 and Answers:  

* **What output do you get from the program?**  
  * ```
    //output:
    Thread is running using a ...!
    ```
* **What is the `() -> { ... }` syntax called?**    
 <br>
    * *It is called a Lambda Expression*  
 <br>
* **How is this code different from creating a class that extends `Thread` or implements `Runnable`?**  
 <br>
   * *Shorter and cleaner code.*
   * *No need for a separate class or explicit `run()` override.*
   * *Lambda directly provides the `run()` body.*