notify

Why doesn't thread wait for notify() ? The thread starts and then goes to the waiting pool, but it proceeds to execute after that moment. public class JavaApplication2 { public static void main(String [] args) { ThreadB b = new ThreadB(); synchronized(b) { b.start(); try { System.out.println("1"); b.wait(); } catch (InterruptedException e) {} System.out.println("Total is: " + b.total); } } } class ThreadB extends Thread { int total; @Override public void run() { synchronized(this) { total += 1; //notify(); } } } You are synchronizing on the thread object itself, which is wrong usage. What

How do I delay a while loop to 1 second intervals without slowing down the entire code / computer it's running on to the one second delay (just the one little loop). Thread.sleep(1000); // do nothing for 1000 miliseconds (1 second) It seems your loop runs on Main thread and if you do sleep on that thread it will pause the app (since there is only one thread which has been paused), to overcome this you can put this code in new Thread that runs parallely try{ Thread.sleep(1000); }catch(InterruptedException ex){ //do stuff } My simple ways to delay a loop. I already put the codes here after

Having this wait declaration: public final native void wait(long timeout) throws InterruptedException; It could exit by InterruptedException, or by timeout, or because Notify/NotifyAll method was called in another thread, Exception is easy to catch but... There is any way to know if the exits cause was timeout or notify? EDIT: This is a tricky way that could work, (although I don't like it) long tBefore=System.currentTimeMillis(); wait(TIMEOUT); if ((System.currentTimeMillis() - tBefore) > TIMEOUT) { //timeout } You can't differentiate between the two unless you provide some additional code.

thread.join() will call thread.wait() , but who and when notifies (either with thread.notify() or notifyAll() ) the thread.wait() ? As we know, thread join will wait for the thread to be completed, but who calls notify on it? Edit: Oh, you are talking about inside of the Thread object itself. Inside of join() we do see a wait() . Something like: while (isAlive()) { wait(0); } The notify() for this is handled by the Thread subsystem. When the run() method finishes, the notify() is called on the Thread object. I'm not sure if the code that actually calls notify() can be seen -- it seems to be

I've written a ListActivity that has a custom list adapter. The list is being updated from a ContentProvider when onCreate is run. I also have a service that gets started when I run the app and it first updates the ContentProvider, then sends a Broadcast that the content has been updated. My ListActivity receives the broadcast and tries to update my ListView. My problem is, I'm getting intermittent errors about the ListView adapter data changing without the ListView being notified. I call the notifyDataSetChanged() method on my list adapter right after I update it. What it seems like is

I need to show a notification from a cron job. My crontab is something like: $ crontab -l # m h dom mon dow command * * * * * Display=:0.0 /usr/bin/notify-send Hey "How are you" I checked /var/log/syslog and the command is actually executed every minute but it doesn't pop up the notification. Can anybody help me understand why? I found the answer: $ crontab -l # m h dom mon dow command * * * * * export DISPLAY=:0.0 && export XAUTHORITY=/home/ravi/.Xauthority && sudo -u ravi /usr/bin/notify-send Hey "How are you" Thanks, Ravi nmax In Ubuntu 14.04 exporting the display did not work for me. Below

I have added a view to the header of listVivew, View TopSearch = (View) View.inflate(this, R.layout.search, null); lv.addHeaderView(TopSearch, null, false); And everything is fine until I try to execute (when data changes) adapter.notifyDataSetChanged(); That always crash my application giving me following error: > java.lang.ClassCastException: android.widget.HeaderViewListAdapter If I remove header view then there is no error. Any suggestions? Thanks. It seems that whenever you use header/footer views in a listview, your ListView gets wrapped with a HeaderViewListAdapter. You can fix this

Why does this test program result in a java.lang.IllegalMonitorStateException ? public class test { static Integer foo = new Integer(1); public static void main(String[] args) { synchronized(foo) { foo++; foo.notifyAll(); } System.err.println("Success"); } } Result: Exception in thread "main" java.lang.IllegalMonitorStateException at java.lang.Object.notifyAll(Native Method) at test.main(test.java:6) You have noted correctly that notifyAll must be called from a synchronized block. However, in your case, because of auto-boxing, the object you synchronized on is not the same instance that you