Java Thread Sleep Example

In Java, using the Thread.sleep() method causes the current thread to be suspended in the execution for a specific period of time. Using this method, provides a facility to allow other threads to get some processor time while the current thread is sleeping.

There are two versions of sleep provided. One specifies the sleep time in milliseconds sleep(long millis) and the other that specifies time to the nanosecond sleep(long millis, int nanos).

However, it must be stated that the these sleep times are not precise and may be slighter longer than the time you have specified. It is highly dependent on the underlying operating system implementation of the scheduler.

SleepThreadExample.java

package com.avaldes.tutorials;

public class SleepThreadExample implements Runnable {
  public void run() {
    for (int i = 0; i<10; i++) {
      try {
        long threadStart = System.currentTimeMillis();
        Thread.sleep(1000);
        System.out.format("Thread %d, duration %d\n", i, (System.currentTimeMillis() - threadStart));
      } catch (InterruptedException e) {
        System.out.format("Thread %s interrupted...", Thread.currentThread().getName());
      }
      
    }
  }
  
  public static void main(String[] args) throws InterruptedException {
    long startTime = 0;
    
    SleepThreadExample ste= new SleepThreadExample();
    Thread t1 = new Thread(ste);
    
    System.out.println("Starting to run thread...");
    startTime = System.currentTimeMillis();
    t1.start();
    t1.join();
    System.out.println("Total Time spent running...: " + (System.currentTimeMillis() - startTime));
    
  }
}

Output

Starting to run thread...
Thread 0, duration 1000
Thread 1, duration 1001
Thread 2, duration 1000
Thread 3, duration 1000
Thread 4, duration 1000
Thread 5, duration 1001
Thread 6, duration 1000
Thread 7, duration 1001
Thread 8, duration 1000
Thread 9, duration 1000
Total Time spent running...: 10007

Important Issues on Thread Sleep

• Thread.sleep() puts current thread to sleep
• Thread.sleep() may throw InterruptedException if sleep was interrupted while active
• Using thread.sleep() pauses the current thread, when the thread awakens the thread goes into ready-to-run state, it is up to the scheduler when thread is to run again
• sleep holds on to any locks it has acquired when while sleeping, using wait() may be a better alternative

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