CODEWITHSUNDEEP
javamultithreadingsleep
Naz
Naz

Reputation: 420

Sleep() method on already sleeping thread

I am working on multi threading and i got a question regard thread sleep method. when i execute sleep()(with time t1) method on already in sleeping thread(with time t2). The total sleep time is t1+t2 or t2(if t2 > t1) or t1 (if t1 > t2):

code:

my thread class:

public class SampleThread extends Thread
{
    public SampleThread(String msg)
    {
        super(msg);
        start();
    }

    public void run()
    {
        try
        {
            SampleThread.sleep(1000);
            System.out.
            println("slept for run");
        }
        catch (InterruptedException e)
        {
            e.printStackTrace();
        }

        System.out.
        println("extends Thread Class is exited");
    }
}

my main method : 

public class TestThreads {

    public static void main(String[] args) {
        SampleThread st = new SampleThread("Extends Thread");
        some(st);

        System.out.println("main thread Executed");
    }
    public static void some(SampleThread t2 ){
        try {
            t2.sleep(10000);
            System.out.println("slept for some" );
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }    
}

result:

slept for run

extends Thread Class is exited

slept for some

main thread Executed

from the result i can say that because sleep time for t2.sleep(10000) is more than SampleThread.sleep(1000) run() method exited first than main method.

But my question is how much time.

Upvotes: 0

Views: 1847

Answers (3)

Zielu
Zielu

Reputation: 8562

Sleep is called by currently running thread, it is not called on the thread object. So your sleep inside run methods pause the Sample thread, the one in the some method pauses your main thread (the one that started the program). Two different execution processes.

The sleep method is actually a static method of the Thread (and you are even calling it as such), which should already indicate for you, that it is not 'bound' to the thread object.

You cannot call sleep twice in the same thread, as to call it has to be awaked. There is no issue of additivity or priority.

So in your code, the second thread starts, executes its run method and pause for shorter time. In the meantime, the main thread continues and pauses for a long time, while the main thread sleeps the created thread finishes its sleeping and then terminates.

Upvotes: 3

fgb
fgb

Reputation: 18559

You can't execute sleep on a sleeping thread because sleep is a static method and can only cause the current thread to sleep.

t2.sleep(10000); causes the main thread to sleep, not t2. It's the same as Thread.sleep(10000).

Upvotes: 1

devshorts
devshorts

Reputation: 8872

You have two different threads and neither blocks each other. So the one thread will wait for 10 seconds, and the other waits for 1 second. The total time you waited depends on which thread you cared about.

Your main waited 10 seconds, it doens't care if the other thread waits for 1 second or a million seconds (if the second thread is set as a daemon thread so it doesn't block the current app).

If your main app spins up a thread that is a daemon, it won't exit until all non-daemon threads are complete. In which case your main app will do its work, and then at the very last line it'll wait until those threads are done.

Upvotes: 1

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