feat: add Thread2 demo with sleep and join for sequential execution

WHAT the code does:
- Defines Thread2 extending Thread.
- Overrides run():
  - Loops from 1 to 5, sleeping 5 seconds between each iteration.
  - Prints the counter and a final message ("Thread is running.....").
- In main():
  - Creates a Thread2 object.
  - Starts the thread with start().
  - Calls join() to ensure main waits until t2 finishes.

WHY this matters:
- Demonstrates thread lifecycle with controlled execution order.
- join() ensures the main thread does not exit before the child thread completes.
- Thread.sleep() introduces artificial delay to visualize scheduling and thread control.

HOW it works:
1. t2.start() → JVM schedules run() in a separate thread.
2. run() executes:
   - For each iteration, sleeps for 5s (TIMED_WAITING state).
   - After waking, prints the current counter.
3. After loop, prints completion message.
4. main thread waits due to join(), preventing premature termination.

Use-case:
- Useful when you want tasks to complete in strict sequence.
- Demonstrates the difference between concurrent execution and forced synchronization with join().

Short key: java-threads sleep-join sequential-demo.

Signed-off-by: https://github.com/Someshdiwan <[email protected]>

Author: Someshdiwan

Section19MultiThreading/MT/src/Thread2.java

@@ -1,24 +1,21 @@
-class Thread2 extends Thread
-{
-    @Override // Thread class ka overridden method. Thread class Methods.
-    public void run()
-    {
+class Thread2 extends Thread {
+    @Override
+    // Thread class ka overridden method. Thread class Methods.
+    public void run() {
         for (int i =1; i<=5; i++){
-            try{
+            try {
                 Thread.sleep(5000);
             }
-            catch(InterruptedException e)
-            {
+            catch(InterruptedException e) {
                 throw new RuntimeException(e);
             }
             System.out.println(i);
         }
         System.out.println("Thread is running.....");
     }
-    public static void main(String[] args) throws InterruptedException
-    {
+    public static void main(String[] args) throws InterruptedException {
         Thread2 t2 = new Thread2();
         t2.start();
         t2.join();
     }
-}
+}