To implement Java Program to implement Multithreading using thread class and runnable interface

Thread1 Class: This class extends Java's built-in Thread class. To make an object of Thread1 executable as a separate thread, it overrides the run() method. The run() method defines the task that this thread will perform. In this case, Thread1 simply prints "Thread 1: " followed by numbers from 1 to 3.

Thread2 Class: This class implements the Runnable interface. The Runnable interface also requires implementing a run() method, which defines the task for the thread. Similar to Thread1, Thread2's run() method prints "Thread 2: " followed by numbers from 1 to 3. The key difference here is that Thread2 is not a Thread itself; it defines a task that a Thread object can execute.

MultipleThread Class (Main Class):

• The main method is the entry point of the program, which initially runs on the main thread.
• Inside main, an object t1 of Thread1 is created. Since Thread1 extends Thread, t1 is already a thread object.
• An object t2_task of Thread2 is created. This t2_task object represents the task to be executed.
• A new Thread object t2 is then created, passing t2_task (the Runnable instance) to its constructor. This effectively "wraps" the Runnable task within a Thread object.
• Finally, t1.start() and t2.start() are called. The start() method is crucial: it initiates a new thread of execution for t1 and t2 respectively and then calls their run() methods. It does not directly call run(). If run() were called directly, the code would execute sequentially on the main thread, defeating the purpose of multithreading.
• Because t1 and t2 are now independent threads, their run() methods will execute concurrently. The Java Virtual Machine's (JVM) thread scheduler will determine when each thread gets CPU time, leading to an interleaved output of "Thread 1" and "Thread 2" messages.

• Create an instance of Thread1 (which is already a Thread object).
• Create an instance of Thread2 (which is a Runnable task).
• Create a new Thread object, passing the Thread2 instance (the Runnable task) to its constructor.
• Invoke the start() method on both Thread objects (t1 and t2). This allocates system resources for new threads and calls their respective run() methods concurrently.