After trying keang's method you could try this if you find it easier.

Code:
Public class t1 implements Runnable()
{
Int curentTime = 0;
Random rand1 = new Random();
Int time1 = 1+rand1.nextInt(100);//the upper limit of time
time1 = time1*1000; // we want to use seconds not milis

Public void Run(){
while(curentTime>100000)
{
//put code to check if time1 == curentTime.. This can also be applied to other timers
// put code to draw circles if needed
Thread.sleep(1000);
CurentTime+= 1000;
}
}
}

But if i were you i'd use keangs way since mine looks a little too complicated