sleep + random

public class CRTest implements Runnable{
 private String id;
 public CRTest(String s){
  id = s;
 }

 public void run() {
 
  for(int i = 0; i < 4; i++){
   int time = (int)(1000*Math.random());
   try {
    Thread.sleep(time);
   } catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
   for(int j = 0; j < 10000000; j++);
    System.out.println(id + " is runing... Time : " + time);
  }
 }
}


public class RunnableTest{
 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub
  CRTest AAA = new CRTest("AAA");
  CRTest BBB = new CRTest("BBB");
 
  Thread t1 = new Thread(AAA);
  Thread t2 = new Thread(BBB);
 
  t1.start();
  t2.start();
 }
}

=======================================
AAA is runing... Time : 313
BBB is runing... Time : 671
AAA is runing... Time : 539
AAA is runing... Time : 239
AAA is runing... Time : 173
BBB is runing... Time : 628
BBB is runing... Time : 25
BBB is runing... Time : 762
========================================