Re: Time transitions in Java
<omkar.tilak@gmail.com> wrote in message
news:1161880627.729430.71710@i42g2000cwa.googlegroups.com...
<snip prior discussion>
Hi Matt,
thanks for all the help. There is still one small issue though. Here
is my code
You're still missing the point below. You don't wait for the timer in a
loop--it defeats the purpose. Your main program waits while reading from
the socket. When the timer goes off, you just have to change state.
class tcpserver
{
String sentence;
String reply;
String state = "START";
public static void main(String args[]) throws Exception
{
Timer timer;
class RemindTask extends TimerTask {
public void run() {
System.out.format("State changed to C");
timer.cancel(); //Terminate the timer thread
You have to actually change state here
state = "C";
And there's no point in terminating the timer because it stops by itself
after this task. The task will run only once anyway. I get the impression
you want to make your main thread stop reading here, though.
}
}
// Create the timer and schedule the task for 5 seconds ahead.
ServerSocket welcome = new ServerSocket(2000);
while(true)
{
Socket connection = welcome.accept();
BufferedReader inClient = new BufferedReader(new
InputStreamReader(connection.getInputStream()));
DataOutputStream out = new
DataOutputStream(connection.getOutputStream());
timer = new Timer();
timer.schedule(new RemindTask(), 5000);
while(timer.isRunning())
{
sentence = inClient.readLine();
timer.cancel();
state = sentence;
System.out.println("State changed to" + sentence);
So instead you really just need
String sentence;
while ((sentence = inClient.readLine()) != null) {
timer.cancel ();
state = sentence;
}
You must be aware that there is a race condition between setting the state
here and setting it in the timer task--what happens if the sentence comes in
just as the timer is activating? You need some synchronization to handle
that.
Also, if the firing of the timer signals that the TCP conversation is over
you should close the socket which will interrupt your main thread, otherwise
it will just wait for the next message. That's done by the code you supply
to the timer.
}
}
}
}
I need to read from socket (inClient.readLine() ) only when the timer
is running (or while the RemindTask is not scheduled).
Sure, but you have to realize that there is necessarily critical point of
transition between when the timer stops and the reading stops. Reading
means waiting and so it cannot stop itself--the timer must stop it. (There
are non-block NIO sockets you can use, but for this case it simply shifts
where the waiting occurs.)
However, Timer
class has no method to do this stuff. Do u think that using javax.swing
Timer might help here ... regards
No. You cannot have a loop that waits on both the timer and on the socket.
The loop you had before will say "timer is running" and so try to read and
then it will wait. Meanwhile the timer will stop and your reader will still
be waiting. You must cancel the reading in the code that signals the timer
has stopped. Furthermore, if the read receives data after the timer has
fired its signal, but before its run method completes, you will get an
incorrect answer. You must look into synchronization so that you can be
sure only one of these happens at a time.
Matt Humphrey matth@ivizNOSPAM.com http://www.iviz.com/