How Interrupt() method is working in Thread

[Kishor Joshi]

Hi there

I am following this article
http://docs.oracle.com/javase/tutorial/essential/concurrency/simple.html


and here is my code

public class SimpleThreads {
	
	// Display a message, preceded by
    // the name of the current thread
    static void threadMessage(String message) {
        String threadName =
            Thread.currentThread().getName();
        System.out.format("%s: %s%n",
                          threadName,
                          message);
    }

    private static class MessageLoop implements Runnable {
        public void run() {
            String importantInfo[] = {
                "Mares eat oats",
                "Does eat oats",
                "Little lambs eat ivy",
                "A kid will eat ivy too"
            };
            try {
                for (int i = 0;i < importantInfo.length;i++) {
                    // Pause for 4 seconds
                    Thread.sleep(4000);
                    // Print a message
                    threadMessage(importantInfo[i]);
                }
            } catch (InterruptedException e) {
                threadMessage("I wasn't done!");
            }
        }
    }

    public static void main(String args[])
        throws InterruptedException {

        // Delay, in milliseconds before
        // we interrupt MessageLoop
        // thread (default one hour).
        long patience = 1000 * 60 * 60;

        // If command line argument
        // present, gives patience
        // in seconds.
        if (args.length > 0) {
            try {
                patience = Long.parseLong(args[0]) * 1000;
            } catch (NumberFormatException e) {
                System.err.println("Argument must be an integer.");
                System.exit(1);
            }
        }

        threadMessage("Starting MessageLoop thread");
        long startTime = System.currentTimeMillis();
        Thread t = new Thread(new MessageLoop());
        t.start();

        threadMessage("Waiting for MessageLoop thread to finish");
        // loop until MessageLoop
        // thread exits
        while (t.isAlive()) {
            threadMessage("Still waiting...");
            // Wait maximum of 1 second
            // for MessageLoop thread
            // to finish.
            t.join(1000);
            if (((System.currentTimeMillis() - startTime) > patience)
                  && t.isAlive()) {
                threadMessage("Tired of waiting!");
                t.interrupt();
                // Shouldn't be long now
                // -- wait indefinitely
                t.join();
            }
        }
        threadMessage("Finally!");
    }
	
	
	

}

I want to know How join() and interrupt() method is working on this program?


I have read above article so no refernce or link to that please.Someone please explain these two methods with reference to this program



Thanks

[Knute Snortum]

I'm not sure what you don't understand. interrupt() tells the thread, "Hey, stop what you're doing." join() says, "Pass control back to me."

I know you said no links, which is annoying, because I think this would help you.

[Kishor Joshi]

Thanks knute
after again review that ref link

Now I understand it

[Henry Wong]

Knute Snortum wrote:interrupt() tells the thread, "Hey, stop what you're doing."

While true, it is a lot more complicated than that. After the other thread gets interrupted, different things can happen, depending on what it was doing when it got interrupted. Also, depending on the JVM version, there can be differences in behavior too (ex. does the OS support interruptable I/O).

Knute Snortum wrote: join() says, "Pass control back to me."

Not sure if I agree with this. I think it is more like, wait until the other thread completes its execution. After all, the thread already has "control" (meaning is executing), or else it wouldn't be able to call the join() method.

Henry

[Knute Snortum]

Thanks Henry. I'm trying to find the balance between complete and easy to understand -- but I should always be accurate.