Concurrency in Java is the ability of a program to run multiple tasks simultaneously. A Thread is the smallest unit of execution. Java provides two ways to create a thread: extending the Thread class or implementing the Runnable interface.

• Extending Thread: Simple but limits multiple inheritance.
• Implementing Runnable: Better practice as it allows inheriting from another class and separates the task from the runner.

1. New: Thread is created but not started.
2. Runnable: After start() is called; ready to run.
3. Running: Processor has selected it to run.
4. Blocked/Waiting: Thread is waiting for a resource or notification.
5. Timed Waiting: Waiting for a specific duration (e.g., Thread.sleep()).
6. Terminated: Thread hasn't finished its task.

java Standard
class MyRunnable implements Runnable {
    public void run() {
        System.out.println("Thread is running...");
    }
}

public class Main {
    public static void main(String[] args) {
        Thread thread = new Thread(new MyRunnable());
        thread.start(); // Correct: calls run() in a new thread
    }
}

• Calling run() instead of start(): Calling run() directly executes the method in the CURRENT thread, not a new one.
• Race Conditions: Multiple threads accessing shared resources without synchronization.
• Starvation: Higher-priority threads consuming all CPU time, leaving lower-priority threads unable to run.