I am trying to do something in Java and I need something to wait / delay for an amount of seconds in a while loop.
while (true) {
if (i == 3) {
i = 0;
}
ceva[i].setSelected(true);
// I need to wait here
ceva[i].setSelected(false);
// I need to wait here
i++;
}
I want to build a step sequencer and I'm new to Java. Any suggestions?
This question is related to
java
wait
sleep
thread-sleep
If you want to pause then use java.util.concurrent.TimeUnit
:
TimeUnit.SECONDS.sleep(1);
To sleep for one second or
TimeUnit.MINUTES.sleep(1);
To sleep for a minute.
As this is a loop, this presents an inherent problem - drift. Every time you run code and then sleep you will be drifting a little bit from running, say, every second. If this is an issue then don't use sleep
.
Further, sleep
isn't very flexible when it comes to control.
For running a task every second or at a one second delay I would strongly recommend a ScheduledExecutorService
and either scheduleAtFixedRate
or scheduleWithFixedDelay
.
For example, to run the method myTask
every second (Java 8):
public static void main(String[] args) {
final ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
executorService.scheduleAtFixedRate(App::myTask, 0, 1, TimeUnit.SECONDS);
}
private static void myTask() {
System.out.println("Running");
}
And in Java 7:
public static void main(String[] args) {
final ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
executorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
myTask();
}
}, 0, 1, TimeUnit.SECONDS);
}
private static void myTask() {
System.out.println("Running");
}
Use Thread.sleep(1000)
;
1000
is the number of milliseconds that the program will pause.
try
{
Thread.sleep(1000);
}
catch(InterruptedException ex)
{
Thread.currentThread().interrupt();
}
You need to use the Thread.sleep()
call.
More info here: http://docs.oracle.com/javase/tutorial/essential/concurrency/sleep.html
Using TimeUnit.SECONDS.sleep(1);
or Thread.sleep(1000);
Is acceptable way to do it. In both cases you have to catch InterruptedException
which makes your code Bulky.There is an Open Source java library called MgntUtils (written by me) that provides utility that already deals with InterruptedException
inside. So your code would just include one line:
TimeUtils.sleepFor(1, TimeUnit.SECONDS);
See the javadoc here. You can access library from Maven Central or from Github. The article explaining about the library could be found here
Use Thread.sleep(100);
.
The unit of time is milliseconds
For example:
public class SleepMessages {
public static void main(String args[])
throws InterruptedException {
String importantInfo[] = {
"Mares eat oats",
"Does eat oats",
"Little lambs eat ivy",
"A kid will eat ivy too"
};
for (int i = 0;
i < importantInfo.length;
i++) {
//Pause for 4 seconds
Thread.sleep(4000);
//Print a message
System.out.println(importantInfo[i]);
}
}
}
Use this:
public static void wait(int ms)
{
try
{
Thread.sleep(ms);
}
catch(InterruptedException ex)
{
Thread.currentThread().interrupt();
}
}
and, then you can call this method anywhere like:
wait(1000);
I know this is a very old post but this may help someone:
You can create a method, so whenever you need to pause you can type pause(1000)
or any other millisecond value:
public static void pause(int ms) {
try {
Thread.sleep(ms);
} catch (InterruptedException e) {
System.err.format("IOException: %s%n", e);
}
}
This is inserted just above the public static void main(String[] args)
, inside the class. Then, to call on the method, type pause(ms)
but replace ms
with the number of milliseconds to pause. That way, you don't have to insert the entire try-catch statement whenever you want to pause.
Source: Stackoverflow.com