Java Thread Control

Introduction

Thread control in Java is essential for managing the execution of multiple threads, enabling concurrent programming. This encompasses starting, pausing, resuming, and stopping threads effectively.

Key Concepts

1. Thread States

• New: A thread that has been created but not yet started.
• Runnable: A thread that is ready to run and waiting for CPU time.
• Blocked: A thread that is waiting for a lock to be released.
• Waiting: A thread that is indefinitely waiting for another thread to perform a specific action.
• Timed Waiting: A thread that waits for another thread to perform an action for a specified duration.
• Terminated: A thread that has completed its execution.

2. Thread Lifecycle

The lifecycle of a thread includes various states and transitions based on specific operations, guiding how threads are managed throughout their lifecycle.

3. Thread Control Methods

• start(): Initiates the execution of the thread.
• sleep(milliseconds): Suspends the thread for a specified period.
• join(): Waits for the thread to finish before proceeding.
• interrupt(): Interrupts a thread that is waiting or sleeping.
• stop(): (Deprecated) Used to terminate a thread but is not recommended due to safety concerns.

Examples

Starting a Thread

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

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

Using sleep()

class SleepThread extends Thread {
    public void run() {
        try {
            System.out.println("Thread is going to sleep");
            Thread.sleep(2000); // Sleep for 2 seconds
            System.out.println("Thread woke up");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

Joining Threads

class JoinThread extends Thread {
    public void run() {
        System.out.println("Join thread is running");
    }
}

public class ThreadJoinExample {
    public static void main(String[] args) throws InterruptedException {
        JoinThread thread = new JoinThread();
        thread.start();
        thread.join(); // Main thread waits for JoinThread to finish
        System.out.println("Main thread resumed after JoinThread completion");
    }
}

Conclusion

Understanding thread control in Java is crucial for effective concurrent programming. By managing thread states and utilizing various thread control methods, developers can create responsive and efficient applications.