/** 操作时间的相关类 方法 具体内容查看相关api */
public class Time { public static void main(String[] args) { Calendar calendar = Calendar.getInstance(); //calendar:日历 getInstance：获取实例 System.currentTimeMillis(); Calendar.getInstance().getTimeInMillis(); Date now = calendar.getTime(); // 获取当前时间 calendar.add(Calendar.DATE, 3); // 50天后的日期 int day = calendar.get(Calendar.DAY_OF_WEEK); //今天是本周的第几天 LocalDateTime localDateTime = LocalDateTime.now(); //获取当地日期时间 DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");//日期格式化 String format = localDateTime.format(formatter); System.out.println(format); SimpleDateFormat time = new SimpleDateFormat("yyyy/MM/dd/hh/mm"); //日期格式化 String l = time.format(now); System.out.println(l); Date date = format.parse(“字符串”);//字符串转日期 //日期转字符串 SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); String firstDayOfMonth = sdf.format(date.getTime()); } }