Solved

Using Thread.notify()

Posted on 2008-10-31
4
467 Views
Last Modified: 2012-05-05
Hi,

I have a background thread which will sleep for 30 seconds at a time. I want to possibly wake it up prematurely from another thread. I thought I could do something like:

    Thread t1 = new Thread() {
        public void run() {
            while (m_run) {
                Thread.sleept(30000);
            }
        }
    }
    t1.start();

   // now main thread continues on, maybe wants to wake the thread up now:
   t1.interrupt();

Is that how you do it? What if the thread is already awake when interrupt() is called, or if it is already exiting sleep() just at the same moment the main thread is calling it? I see you can also do a wait()/notfiy() but then you need an additional object to act as the guard?

Thanks
0
Comment
Question by:DJ_AM_Juicebox
  • 2
  • 2
4 Comments
 

Author Comment

by:DJ_AM_Juicebox
ID: 22853447
To follow up, I may have multiple threads wanting to wake that one background thread up - so a request to wake up prematurely may come from a few different sources -
0
 

Author Comment

by:DJ_AM_Juicebox
ID: 22853694
Hmm so using wait/notify works too, is this the correct usage?
if (m_thread == null) {
    m_waitGuard = new Object();
    
    m_thread = new Thread() {
        public void run() {
            while (m_run) {
                try { 
                    synchronized (m_waitGuard) {  
                        m_waitGuard.wait(30000);
                    }
                }
                catch (InterruptedException ex) {
                    Log.d("**", "I woke up!");
                }
            }
            Log.d("**", "Thread is exiting..");
        }
    };
    m_thread.start();
}
 
 
// Then on some event like a button press, I can prematurely wake the thread up:
public void onBtnPress()
{
    synchronized (m_waitGuard) {
        m_waitGuard.notifyAll();
    }
}

Open in new window

0
 
LVL 86

Accepted Solution

by:
CEHJ earned 500 total points
ID: 22855000
I see you can also do a wait()/notfiy() but then you need an additional object to act as the guard?

That's the way to do it in Java without using the java.util.concurrency package and it can be seen here:

http://technojeeves.com/joomla/index.php/free/61-wait-and-notify-in-java

but you don't *have* to have a separate lock object - it can be done using the objects you already have.
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 22896643
:-)
0

Featured Post

Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Java contains several comparison operators (e.g., <, <=, >, >=, ==, !=) that allow you to compare primitive values. However, these operators cannot be used to compare the contents of objects. Interface Comparable is used to allow objects of a cl…
In this post we will learn how to connect and configure Android Device (Smartphone etc.) with Android Studio. After that we will run a simple Hello World Program.
This theoretical tutorial explains exceptions, reasons for exceptions, different categories of exception and exception hierarchy.
Viewers will learn how to properly install Eclipse with the necessary JDK, and will take a look at an introductory Java program. Download Eclipse installation zip file: Extract files from zip file: Download and install JDK 8: Open Eclipse and …

820 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question