The Timer class schedules a task to run at a given time once or repeatedly. It can also run in the background as a daemon thread. To associate Timer with a daemon thread, there is a constructor with a boolean value. The Timer schedules a task with fixed delay as well as a fixed rate. In a fixed delay, if any execution is delayed by System GC, the other execution will also be delayed and every execution is delayed corresponding to previous execution. In a fixed rate, if any execution is delayed by System GC then 2-3 execution happens consecutively to cover the fixed rate corresponding to the first execution start time. The Timer class provides a cancel() method to cancel a timer. When this method is called, the Timer is terminated. The Timer class executes only the task that implements the TimerTask.
Example
import java.util.*; public class TimerThreadTest { public static void main(String []args) { Task t1 = new Task("Task 1"); Task t2 = new Task("Task 2"); Timer t = new Timer(); t.schedule(t1, 10000); // executes for every 10 seconds t.schedule(t2, 1000, 2000); // executes for every 2 seconds } } class Task extends TimerTask { private String name; public Task(String name) { this.name = name; } public void run() { System.out.println("[" + new Date() + "] " + name + ": task executed!"); } }
Output
[Thu Aug 01 21:32:44 IST 2019] Task 2: task executed! [Thu Aug 01 21:32:46 IST 2019] Task 2: task executed! [Thu Aug 01 21:32:48 IST 2019] Task 2: task executed! [Thu Aug 01 21:32:50 IST 2019] Task 2: task executed! [Thu Aug 01 21:32:52 IST 2019] Task 2: task executed! [Thu Aug 01 21:32:53 IST 2019] Task 1: task executed! [Thu Aug 01 21:32:54 IST 2019] Task 2: task executed! [Thu Aug 01 21:32:56 IST 2019] Task 2: task executed! [Thu Aug 01 21:32:58 IST 2019] Task 2: task executed! [Thu Aug 01 21:33:00 IST 2019] Task 2: task executed!