Understanding Multithreading in Java with Examples

Multithreading in Java allows multiple parts of a program, called threads, to run concurrently. This helps make efficient use of the CPU and improves the performance of applications that perform multiple tasks at once.

Ways to Create a Thread

1. Extending the Thread Class

class MyThread extends Thread {
    public void run() {
        System.out.println("Thread running: " + Thread.currentThread().getId());
    }
}

MyThread t1 = new MyThread();
t1.start();

2. Implementing the Runnable Interface

class MyRunnable implements Runnable {
    public void run() {
        System.out.println("Runnable running: " + Thread.currentThread().getId());
    }
}

Thread t2 = new Thread(new MyRunnable());
t2.start();

Thread Lifecycle

• New — thread object created but not yet started
• Runnable — thread is ready to run and waiting for CPU time
• Running — thread is currently executing
• Blocked/Waiting — thread is paused, waiting for a resource or signal
• Terminated — thread has finished execution

Why Use Multithreading?

• Improves performance by running independent tasks in parallel
• Keeps applications responsive, since long tasks don't block the entire program
• Makes better use of multi-core processors