java获取当中系统时间

方法一：

//        获取当前时间
        Date day=new Date();
        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");  //2020-11-03
        String format = df.format(day);
        System.out.println(format);

方法二：

  SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String format = df.format(System.currentTimeMillis());
        System.out.println(format);

方法三：

//        获取当前时间
        Calendar c = Calendar.getInstance();//可以对每个时间域单独修改   对时间进行加减操作等
        int year = c.get(Calendar.YEAR);
        int month = c.get(Calendar.MONTH);
        int date = c.get(Calendar.DATE);
        int hour = c.get(Calendar.HOUR_OF_DAY);
        int minute = c.get(Calendar.MINUTE);
        int second = c.get(Calendar.SECOND);
        System.out.println(year + "/" + month + "/" + date + " " +hour + ":" +minute + ":" + second);