Clean up the oldest data in mongodb

public class MongoDBDataClean {

	public static void main(String[] args) throws Exception {
		
		TimerTask task = new TimerTask(){

			@Override
			public void run() {
               clearMongoData();
			}

			private void clearMongoData() {
				SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
				System.out.println("Start at : "+sdf.format(new Date()));
				
				MongoTemplate mongoTemplate = (MongoTemplate) SpringApplicationContextUtil.getInstance().getBean(
		                "mongoTemplate");
				Query query = new Query();
				query.sort().on("_id", Order.ASCENDING);
				List<HistoryEntry> list = mongoTemplate.find(query.limit(50000), HistoryEntry.class);
				
				System.out.println("Count end at :"+list.size()+"      "+sdf.format(new Date()));
				
				for(int i =0 ; i < list.size() ; i ++){
					mongoTemplate.remove(list.get(i));
				}
				System.out.println("Success end at :"+sdf.format(new Date()));
			}
		};
		
		Timer timer = new Timer ();
		long delay = 0;
		long intevalPeriod = 60*1000;
		timer.scheduleAtFixedRate(task, delay, intevalPeriod);
	}
}