Java Timer

[sconeek]

Hi all,

I am writing a Java app, where I need to wait for 10 seconds after a
condition holds good and then check if the same condition still holds
true and if yes then do something.

Essentially I have this,
if (mDt.getTime() == lsEtTSt.getTime()) {
// wait for 10 seconds

// check for the condition again

// Do something
}

I dont want to use Thread.sleep. If somebody could suggest a loop or
something which goes on for 10seconds that would be really great.

thanks.

 

[sconeek]

I think the timer class might help me. I am thinking of even creating a
loop for 10 seconds. but what should i do within the loop for that
time. any help please.

 

[hiwa]

Do you have some reason for not using java.util.Timer?

 

[sconeek]

I wouldnt mind using that either. i just need to know how to implement
it.

 

[Luc The Perverse]

I wouldnt mind using that either. i just need to know how to implement
it.

LOL

Here is an example

import java.lang.Thread;

public class BeerSong implements Runnable {
Thread runner;
BeerSong(){
if (runner == null) { //start the song
runner = new Thread(this);
runner.start();
}
}
public void run() {
int beerNum = 99;
String word = "bottles";

while (beerNum > 0 && runner != null){
WaitAMoment();
if (beerNum == 1)
word = "bottle";
System.out.println(beerNum + " " + word + " of beer on the wall");
System.out.println(beerNum + " " + word + " of beer.");
System.out.println("Take one down");
System.out.println("Pass it around.");
beerNum = beerNum - 1;
if (beerNum > 0)
System.out.println(beerNum + " " + word + " of beer on the wall");
else
System.out.println("No more bottles of beer on the wall");
}

}
protected void WaitAMoment() {
try {
Thread.sleep(300);
} catch (InterruptedException e) { };
}
public static void main (String[] args) {
new BeerSong();
}
}


I like to put my sleep into it's own function

Of course, you don't need to make a special thread to wait.

You could just insert this code

try {
java.lang.Thread.currentThread().sleep(10000);
} catch (Exception e) {
// e.printStackTrace();
}

Just replace the 10000 with the number of milliseconds you want to wait

This is much more efficient than a loop.

 

[sconeek]

I have tried using Thread.sleep() but I would like to use a loop of
some kind, as i dont want to try it that way. any other ideas?.
something which is not very resource intensive and all it does is loop
a variable for 10 secs and once thats over does what i want it to do.

 

[sconeek]

I want to try something like this,
for (int i=0;i<10000;i++) {
not sure what to do while its looping????
}
Then do whatever.

any help on what should go inside the for loop and if this will
actually loop for 10secs or not. thanks to all who reply.

 

[Knute Johnson]

I want to try something like this,
for (int i=0;i<10000;i++) {
not sure what to do while its looping????
}
Then do whatever.

any help on what should go inside the for loop and if this will
actually loop for 10secs or not. thanks to all who reply.

You asked how to do it and even got some examples. Now you are telling
us you want to do it with a loop. The reason you aren't getting a loop
as an answer is that isn't the way to do it. Use Thread.sleep() or use
java.util.Timer but forget the loop.

 

[sconeek]

ok my bad. can you tell me whats the best approach with
java.util.Timer. thanks again. I will try and attempt it in the
meantime.

 

[Roedy Green]

I am writing a Java app, where I need to wait for 10 seconds after a
condition holds good and then check if the same condition still holds
true and if yes then do something.

Essentially I have this,
if (mDt.getTime() == lsEtTSt.getTime()) {
// wait for 10 seconds

// check for the condition again

// Do something
}

I dont want to use Thread.sleep. If somebody could suggest a loop or
something which goes on for 10seconds that would be really great.

why not sleep? if you have only one test.

The alternative is to use a Timer that get triggered every 10 seconds.
The advantage here is you can use the same Timer thread to manage
several different periodic tests. See
http://mindprod.com/jgloss/timer.html

 

[Roedy Green]

I want to try something like this,
for (int i=0;i<10000;i++) {
not sure what to do while its looping????
}
Then do whatever.

The problem with this approach is you will gobble up all the CPU time
to accomplish nothing. That was the way you did things in DOS when
there were no other tasks that could use the CPU.

 

[zero]

The problem with this approach is you will gobble up all the CPU time
to accomplish nothing. That was the way you did things in DOS when
there were no other tasks that could use the CPU.

Which is also why for example old DOS games can't run on new computers.
The time needed to loop is to hardware dependent.

 

[Brandon McCombs]

I want to try something like this,
for (int i=0;i<10000;i++) {
not sure what to do while its looping????
}
Then do whatever.

any help on what should go inside the for loop and if this will
actually loop for 10secs or not. thanks to all who reply.

FYI, the iterations in a loop do not equal a millisecond so you can't
use them as a timer. It gets executed as fast as the CPU can execute it.

 

[Luc The Perverse]

*snip*

You said you want to wait.

If there is some reason you are trying to use a loop - some specific thing
you are trying to accomplish then maybe you need to relate that better to
use so we are able to help you.

I can imagine a "loop for a specific amount of time" scenario. Let's say
you wanted to calculate an irrational value to a certain number of digits,
in a finite amount of time, or calculate the best chess move (this may be a
more logical example). You could allot the computer a certain number of
seconds to perform the task and have it loop until the time was expired.

But that is not what you said. You said you wanted a delay. A delay is
never better implemented with a loop than a sleep call.

Of course we are resisting to tell you how to do it, because . . . we are
afraid that you are going to do it that way. It would be better if you
could explain why you want to use a loop, and/or if we could explain to you
why a loop is a bad idea.

 

[Prashant Parashar]

Thread.sleep() is best. Forget Timer or loop to introduce the delay.

Thread.sleep would take least resource (or none). Timer will require a
new thread (thus the memory). Loop will eat up all the CPU time.

 

[Thomas Hawtin]

Thread.sleep() is best. Forget Timer or loop to introduce the delay.

Thread.sleep would take least resource (or none). Timer will require a
new thread (thus the memory). Loop will eat up all the CPU time.

I prefer Object.wait. In order to get a program with sleep to exit, say,
in a timely fashion, you need to use Thread.interrupt. Thread.interrupt
comes with a host of problems, including disruption of class loading.

I may be in a minority on this one.

Tom Hawtin

 

[sconeek]

the main purpose of me doing the wait is that, the system is doing
something while the program is waiting (or sleeping) and after that
time has elapsed I want to double check the information received and
then perform action based on that second information.

I do not want to perform any action on the first set of input, as I
would like to double check that information and then do something. I
hope this helps. The main point of the wait process is to wait for x
number of seconds and then check for information again, and if that
information matches what I am after then I will do something.

I have tried using thread.sleep but the information actually gets
updated while the thread is sleeping, I want it to do nothing till x
number of seconds and then check again for information and if
satisified with second level of information, do something.

i would really appreciate all help I can get.

 

[Luc The Perverse]

You want to suspend the entire process, rather than just the current
thread? There is no good way to do that.

I doubt that is what he meant.

I think he is looking for some kind of an input interrupt system. Where the
input is coming from, I don't know because he hasn't told us.

I think I finally understand what he is trying to ask. He wants to wait up
to a specific amount of time for something to happen, the loop would be used
for checking if something had happened. It seems like a reasonable
request, if one has never heard of the "right" way of doing it.

Now - I have never done any significant multithreaded Java application. Is
it possible to interrupt sleep directly without killing the thread, or is
there a better function to use? (I know in MFC C++ there were Semaphores
and mutex objects, and you could wait for them to be in a triggered state.)

 

[Luc The Perverse]

I don't remember enough of MFC to recall exactly how MFC wrapped the
Windows API here. As far as the API itself, though, the equivalent to
Win32 mutexes and critical sections are synchronized blocks, used in
different ways. The equivalents of events are Object.wait and
Object.notify (as implemented in certain ways, and of course combined
with synchronized blocks as they always are).

Semaphores are slightly more complex and not available directly in the
language, but they can be easily built from the monitor functions above.
Beginning with Java 1.5, the java.util.concurrent package contains an
implementation of semaphores. Also, Java 1.5 contains an implementation
of mutexes (known as locks) that are NOT tied to lexical scope in the
language in the manner that synchronized blocks are.

If my ignorance is obvious you can tell me to shutup . . but . . .

I followed you up until this point "that are NOT tied to lexical scope in
the language in the manner that synchronized blocks are."

 

[Chris Smith]

I have tried using thread.sleep but the information actually gets
updated while the thread is sleeping, I want it to do nothing till x
number of seconds and then check again for information and if
satisified with second level of information, do something.

You want to suspend the entire process, rather than just the current
thread? There is no good way to do that.

--
www.designacourse.com
The Easiest Way To Train Anyone... Anywhere.

Chris Smith - Lead Software Developer/Technical Trainer
MindIQ Corporation