complete theoretical part

Report.md

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+## Theoretical Questions
+### 1. `start()` vs `run()`
+- What output do you get from the program? Why?
+    ```
+    Calling run()
+    Running in: main
+    Calling start()
+    Running in: Thread-2
+    ```
+    → When `t1.run()` is called directly, we're calling the `run()` method like a 
+normal method and no new thread is created. The `run()` method is executed on the 
+current thread (main); so `Thread.currentThread().getName()` returns "main".
+<br/> When `t2.start()` is called: `start()` creates a new thread named "Thread-2".
+The new thread automatically calls  `run()` so `Thread.currentThread().getName()` returns "Thread-2".
+
+- What’s the difference in behavior between calling `start()` and `run()`?
+→ `start()`: creates a new thread and is executed on a new thread.
+  `run()`: method doesn't create new thread and is executed on the current thread.
+
+### 2. Daemon Threads
+
+- What output do you get from the program? Why?
+    ```
+    Main thread ends.
+    Daemon thread running...
+    ```
+    → The thread is set as a Daemon thread. The main thread ends immediately after
+printing "Main thread ends." and the JVM exits without waiting for the daemon thread to complete its loop.
+
+- What happens if you remove `thread.setDaemon(true)`?
+
+  → The thread becomes a user thread. The main thread still ends,
+but the JVM will not exit because there is still a live user thread. 
+The program will print all 20 "Daemon thread running..." messages.
+- What are some real-life use cases of daemon threads?
+
+    → Spell Checker / Grammar Checker in Word.
+
+### 3. A shorter way to create threads
+
+- What output do you get from the program?
+    ```
+    Thread is running using a ...!
+    ```
+- What is the `() -> { ... }` syntax called?
+
+    → lambda expression
+
+- How is this code different from creating a class that extends `Thread` or implements `Runnable`?
+  
+    → The code uses a lambda expression to define the `run()` method inline. 
+When you extend `Thread`, you must create a separate subclass, override the `run()` method,
+and then instantiate that subclass. This gives you the ability to add 
+new fields or methods to your thread class, but it also means you cannot extend any other class.
+When you implement `Runnable` using an anonymous class (the old way before lambdas), you write:
+
+    `new Runnable() { public void run() { ... } }`.