Day-99 Multithreading in Java

Multithreading is the process of executing multiple threads simultaneously.

• A thread is the smallest unit of execution.
• Java provides strong multithreading support via the Thread class and Runnable interface.
• It helps in better CPU utilization and improved application performance.

Ways to Create a Thread

There are two main ways to create a thread in Java:

a) Extending the Thread Class

class MyThread extends Thread {
    public void run() {
        System.out.println("Thread running using Thread class!");
    }
}

public class ThreadDemo {
    public static void main(String[] args) {
        MyThread t1 = new MyThread();
        t1.start(); // Start the thread
    }
}

b) Implementing the Runnable Interface

class MyRunnable implements Runnable {
    public void run() {
        System.out.println("Thread running using Runnable interface!");
    }
}

public class RunnableDemo {
    public static void main(String[] args) {
        Thread t1 = new Thread(new MyRunnable());
        t1.start();
    }
}

Thread Lifecycle

A thread passes through these states:

New → Runnable → Running → Waiting → Terminated

• New: Thread object created but not started.
• Runnable: Thread is ready to run but waiting for CPU scheduling.
• Running: Thread is currently executing.
• Waiting/Timed Waiting: Thread is paused temporarily.
• Terminated: Thread has finished execution.

Common Thread Methods

1. start() → begin thread execution
2. run() → contains the logic of the thread
3. sleep(ms) → pause thread for given milliseconds
4. join() → wait for a thread to finish
5. isAlive() → check if thread is running

Synchronization

When multiple threads access a shared resource, race conditions may occur.

• synchronized keyword ensures that only one thread can access a resource at a time.

Conclusion

• Threads allow concurrent execution.
• Two ways to create threads: Thread class & Runnable interface.
• Use synchronization to prevent race conditions.
• Multithreading is widely used in games, web servers, and real-time applications.