编辑代码

import java.text.DecimalFormat;
import java.util.Calendar;
import java.util.Date;
import java.text.SimpleDateFormat;
import java.text.ParseException;

class Main {
	public static void main(String[] args) throws ParseException {

    SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    Date date = df.parse("2021-08-29 00:00:00");
    long tempDayTimeMillis = date.getTime();
    //long tempDayTimeMillis =  new Date().getTime();
    long currentDayTimeMills = new Date().getTime();
    long dayTimeMills = currentDayTimeMills-tempDayTimeMillis;
    System.out.println(dayTimeMills);
    System.out.println(( 0<= dayTimeMills  && dayTimeMills <= (1000 *3600 *24)));

    long days = new Date().getTime() / 1000 / 3600 / 24 - date.getTime() / 1000 / 3600 / 24;
    System.out.println(days);
	}
  
}