Preventing Thread Execution: yield(), join(), and sleep() 😴

In Java, thread execution can be controlled using methods like yield(), join(), and sleep(). These methods help in pausing, rescheduling, or waiting for other threads, ensuring efficient execution.

1. Why Control Thread Execution? 🤔

If threads execute without coordination, it can lead to inefficient resource usage, race conditions, or unexpected behavior.

Real-Life Example 🏃💨

In a relay race:

• A runner may slow down (yield) to let another runner take the lead.
• A runner must wait (join) for their teammate before continuing.
• A runner can take a short break (sleep) before starting again.

2. Using yield() 🔄

The yield() method hints to the scheduler that the current thread is willing to pause and allow other equal-priority threads to run.

Example Code 📝

class YieldExample extends Thread {
    public void run() {
        for (int i = 0; i < 5; i++) {
            System.out.println(Thread.currentThread().getName() + " is executing");
            Thread.yield(); // Hints that other threads can run
        }
    }
    public static void main(String[] args) {
        YieldExample t1 = new YieldExample();
        YieldExample t2 = new YieldExample();
        t1.start();
        t2.start();
    }
}

📌 Note: yield() does not guarantee that another thread will run—it just gives a chance to equal-priority threads.

3. Using join() 🛑

The join() method ensures that a thread waits for another thread to complete before proceeding.

Example Code 📝

class JoinExample extends Thread {
    public void run() {
        for (int i = 1; i <= 5; i++) {
            System.out.println(Thread.currentThread().getName() + " - " + i);
            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {}
        }
    }
    public static void main(String[] args) {
        JoinExample t1 = new JoinExample();
        JoinExample t2 = new JoinExample();
        t1.start();
        try {
            t1.join(); // Main thread waits for t1 to finish
        } catch (InterruptedException e) {}
        t2.start(); // t2 starts only after t1 finishes
    }
}

✅ Use Case: Ensuring that one thread completes before another starts.

4. Using sleep() ⏳

The sleep() method pauses execution for a specified time, allowing other threads to run.

Example Code 📝

class SleepExample extends Thread {
    public void run() {
        for (int i = 1; i <= 3; i++) {
            try {
                Thread.sleep(1000); // Pauses execution for 1 second
            } catch (InterruptedException e) {}
            System.out.println(Thread.currentThread().getName() + " - " + i);
        }
    }
    public static void main(String[] args) {
        SleepExample t1 = new SleepExample();
        t1.start();
    }
}

🔹 Use Case: Simulating delays or pauses in execution.

5. Key Differences 🏆

6. Conclusion 🎯

• Use yield() to allow other threads a chance to run.
• Use join() to ensure one thread completes before another starts.
• Use sleep() to introduce delays in execution.

Proper thread control improves efficiency and prevents unnecessary CPU usage in Java applications! 🚀