The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
Thread.sleep
causes the current thread to suspend execution for a specified period. This is an efficient means of making processor time available to the other threads of an application or other applications that might be running on a computer system. The sleep
method can also be used for pacing, as shown in the example that follows, and waiting for another thread with duties that are understood to have time requirements, as with the SimpleThreads
example in a later section.
Two overloaded versions of sleep
are provided: one that specifies the sleep time to the millisecond and one that specifies the sleep time to the nanosecond. However, these sleep times are not guaranteed to be precise, because they are limited by the facilities provided by the underlying OS. Also, the sleep period can be terminated by interrupts, as we'll see in a later section. In any case, you cannot assume that invoking sleep
will suspend the thread for precisely the time period specified.
The
example uses SleepMessages
sleep
to print messages at four-second intervals:
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]); } } }
Notice that main
declares that it throws InterruptedException
. This is an exception that sleep
throws when another thread interrupts the current thread while sleep
is active. Since this application has not defined another thread to cause the interrupt, it doesn't bother to catch InterruptedException
.