1초에 한 번씩 시간 업데이트하여

import java.util.Calendar;
import java.util.Timer;
import java.util.TimerTask;

public class timer {

	public static void main(String() args) {

		Timer t = new Timer();
		Tictoc tt = new Tictoc();
		tt.schedule(tt, 1000, 1000);
		
	}

}

class Tictoc extends TimerTask {
	public void run() {
		printDays();
	}
	private void printDays() {
		Calendar cal = Calendar.getInstance();
		System.out.print(cal.get(Calendar.YEAR)+"년 ");
		System.out.print(cal.get(Calendar.MONTH)+"월 ");
		System.out.print(cal.get(Calendar.DATE)+"일 ");
		System.out.print(cal.get(Calendar.HOUR)+"시 ");
		System.out.print(cal.get(Calendar.MINUTE)+"분 ");
		System.out.println(cal.get(Calendar.SECOND)+"초");
		
	}
}