java.util.TimerTask is an abstract class that implements Runnable interface

and we need to extend this class to create our own TimerTask that can be scheduled using java Timer class and

java.util.Timer class can be used to schedule a task to

be run one-time or to be run at regular intervals at certain time in future. 

https://stackoverflow.com/questions/4544197/how-do-i-schedule-a-task-to-run-at-periodic-intervals