Timer

public class Reminder{
    Timer timer;
    protected int start=0;
    protected int end=0;

    public Reminder(int s,int e,int frequency){
       start = s;
       end = e;
       timer = new Timer();
       timer.schedule(new ReminderTask(),0,frequency*1000);
    }
    public class ReminderTask extends TimerTask{
        
        public void run(){
            
            System.out.println("doing something");
            Calendar cal = Calendar.getInstance();
            if(cal.get(Calendar.HOUR_OF_DAY) > end){
                int hour = cal.get(Calendar.HOUR_OF_DAY);   
                //计算需要睡眠多久
                while(true){
                    try {
                        Thread.sleep((start+24-hour)*1000);
                        break;
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                        break;
                    }
                }
            }
        }

        
        }

public static void main(String args[]){
    
        new Reminder(8,16,1);
    }
}