How to Gracefully Start, Stop, and Restart Threads in Java?

Threadlifecycle in Java: Start, Stop, Restart

Thread management is crucial for concurrency in Java. In this article, we address the conundrum of starting, stopping, and restarting a thread.

Starting a Thread

Instantiating a Runnable or Callable class and passing it to a Thread object is the conventional way to start a thread.

Stopping a Thread

Despite common misconceptions, stopping a thread abruptly is not recommended. Instead, signal the thread to terminate gracefully:

1. Define a volatile boolean variable to indicate the desired termination state (isTerminating).
2. Check isTerminating periodically within the thread's run method.
3. When isTerminating is true, stop the thread's execution.

Restarting a Thread

Once a thread stops, it cannot be directly restarted. However, consider these options:

• Create a New Thread: Terminate the existing thread and create a new one with the same task.
• Suspend/Resume Thread: Instead of stopping the thread, suspend it. When it needs to resume, notify it to continue execution. This ensures the thread remains alive and avoids the overhead of creating and destroying threads repeatedly.

Example of Terminating a Thread:

public class Task implements Runnable {

    private volatile boolean isTerminating;

    @Override
    public void run() {
        while (!isTerminating) {
            // Perform task
        }
        System.out.println("Thread terminated.");
    }

    public void setIsTerminating(boolean terminating) {
        this.isTerminating = terminating;
    }
}

In the main приложение, call setIsTerminating(true) and join() to wait for the thread to terminate gracefully.

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