Java Thread Sleep

    synchronized(lockedObject) {   
      Thread.sleep(1000); // It does not release the lock on lockedObject.
      // So either after 1000 miliseconds, current thread will wake up, or after we call 
      //t. interrupt() method.

Example: Create a class FirstThread.java as below.

package org.arpit.java2blog.thread;

public class FirstThread implements Runnable{

 public void run()
 {
  System.out.println("Thread is running");
 }

}

Create main class named ThreadSleepExampleMain.java

package org.arpit.java2blog.thread;

public class ThreadSleepExampleMain {

 public static void main(String args[])
 {
  FirstThread ft= new FirstThread();

  Thread t=new Thread(ft);
  t.start();
  long startTime=System.currentTimeMillis();
  try {
                // putting thread on sleep
   Thread.sleep(1000);
  } catch (InterruptedException e) {
   e.printStackTrace();
  }
  long endTime=System.currentTimeMillis();
  long timeDifference=(endTime-startTime);
  System.out.println("Time difference between before and after sleep call: "+timeDifference);
 }

}

When you run above program, you will get following output.

You can see there is a delay of 1000 milliseconds (1 sec). As mentioned earlier, its accuracy depends on system timers and schedulers.

How Thread Sleep Works

Thread.sleep() works with thread scheduler to pause current thread execution for specific period of time. Once thread wait period is over, the thread’s state is changed to runnable again and it is available for further execution for CPU.