Java中的日期时间介绍

心已赠人 2022-09-23 09:29 192阅读 0赞

public class TestDate {
        public static void main(String[] args){
    
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            Calendar calendar = Calendar.getInstance();
    
            // 1.得到当前时间
            System.out.println(sdf.format(calendar.getTime()));
    
            // 2.得到上一个月的月初
            calendar.add(Calendar.MONTH, -1);
            calendar.set(Calendar.DAY_OF_MONTH, calendar.getActualMinimum(Calendar.DAY_OF_MONTH));
            Date strDateFromDefault = calendar.getTime();
            String monthFirstDay = sdf.format(strDateFromDefault.getTime());
            System.out.println(monthFirstDay);
    
            // 3.得到上一个月的月末
            calendar.set(Calendar.DAY_OF_MONTH, calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
            Date strDateToDefault = calendar.getTime();
            String monthLastDay = sdf.format(strDateToDefault.getTime());
            System.out.println(sdf.format(strDateToDefault.getTime()));
    
            // 4.ͨ通过某个月的第一天得到对应这个月的最后一天【日期的截取】
            String monthBeginDay = "2015-11-01";
            String month = monthBeginDay.substring(5, 7);
            int lastDay = (month.indexOf(0) == 0) ? month.indexOf(1) : Integer.parseInt(month);
            calendar.set(Integer.parseInt(monthBeginDay.substring(0, 4)), lastDay-1, 1);
            calendar.set(Calendar.DAY_OF_MONTH, calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
            Date strDate = calendar.getTime();
            monthLastDay = sdf.format(strDate.getTime());
    
            System.out.println(monthLastDay);
    
            // 5.判断某一个日期是否符合当前格式，用正则表达式
            String monthBeginDay = "2015-07";
            if(!monthBeginDay.matches("^[0-9]{4,4}-[0-1][1-9]$")){
               System.out.println("格式不正确ȷ ");
            }else {
                System.out.println("格式正确");
            }
    
            // 6.判断某一个日期是否符合当前格式，用正则表达式
              String eL = "[0-9]{4}-[0-1][0-9]";
              Pattern p = Pattern.compile(eL);
              Matcher m = p.matcher("2015-03000");
              boolean dateFlag = m.matches();
              if (!dateFlag) {
                System.out.println("格式错误");
              }
              else{
                System.out.println("格式正确");
              }
    
            //7.得到某个月的月初和月末
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            Calendar calendar = Calendar.getInstance();
            calendar.set(Calendar.DAY_OF_MONTH, calendar.getActualMinimum(Calendar.DAY_OF_MONTH));
            String monthFirstDay = sdf.format(calendar.getTime());
            System.out.println(monthFirstDay);
    
            calendar.set(Calendar.DAY_OF_MONTH, calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
            String monthLastDay = sdf.format(calendar.getTime());
            System.out.println(monthLastDay);
    
            //8.增加月份或者天数后的日期
            Calendar calendar = Calendar.getInstance();
            calendar.setTime(calendar.getTime());//这里的时间必须是Date型
            calendar.add(Calendar.MONTH, 1);
            System.out.println("增加月份后的日期："+calendar.getTime());
    
            Calendar calendar = Calendar.getInstance();
            calendar.setTime(calendar.getTime());
            calendar.add(Calendar.DAY_OF_MONTH, 100);
            System.out.println("增加天数后的日期："+calendar.getTime());
    
           // 9.获取当前时间对应的本周星期一和星期天的日期
            Calendar cal =Calendar.getInstance();
            SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
            cal.setTime(cal.getTime());
            cal.add(Calendar.DAY_OF_WEEK, 2);
            System.out.println("增加月份后的日期："+df.format(cal.getTime()));
             //判断要计算的日期是否是周日，如果是则减一天计算周六的，否则会出问题，计算到下一周去了
            int dayWeek = cal.get(Calendar.DAY_OF_WEEK);//获得当前日期是一个星期的第几天
            if(1 == dayWeek) {
                cal.add(Calendar.DAY_OF_MONTH, -1);
            }
            cal.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY); //获取本周一的日期
            System.out.println("本周星期一的日期："+df.format(cal.getTime()));
            //这种输出的是上个星期周日的日期，因为老外那边把周日当成第一天
            cal.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
            //增加一个星期，才是我们中国人理解的本周日的日期
            cal.add(Calendar.WEEK_OF_YEAR, 1);
            System.out.println("本周星期天的日期："+df.format(cal.getTime()));
    
            //10.获取当前时间对应的下周星期一和星期天的日期
            Calendar cal =Calendar.getInstance();
            //SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
            DateTool df = new DateTool();
            cal.setTime(cal.getTime());
            cal.add(Calendar.DAY_OF_WEEK, 5);
            System.out.println("增加月份后的日期："+df.format(cal.getTime()));
             //判断要计算的日期是否是周日，如果是则减一天计算周六的，否则会出问题，计算到下一周去了
            int dayWeek = cal.get(Calendar.DAY_OF_WEEK);//获得当前日期是一个星期的第几天
            System.out.println(dayWeek);
            if (dayWeek != 1) {
                cal.add(Calendar.DAY_OF_MONTH, 9 - dayWeek);
            }
            cal.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY); //获取本周一的日期
            System.out.println("下周星期一的日期："+df.format(cal.getTime()));
            //这种输出的是上个星期周日的日期，因为老外那边把周日当成第一天
            cal.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
            //增加一个星期，才是我们中国人理解的本周日的日期
            cal.add(Calendar.WEEK_OF_YEAR, 1);
            System.out.println("下周星期天的日期："+df.format(cal.getTime()));
    
            String releaseDate = df.format(cal.getTime());
            String releaseDateNextSundaySql = "TO_DATE('"+releaseDate.substring(0, 12)+"', 'Month dd, YYYY')";
            System.out.println("下周星期天的日期："+releaseDateNextSundaySql);
    
             //11.将date型时间的时分秒置为0
             Calendar calendar =Calendar.getInstance();
             calendar.setTime(calendar.getTime());
             calendar.set(Calendar.HOUR_OF_DAY, 0);
             calendar.set(Calendar.MINUTE, 0);
             calendar.set(Calendar.SECOND, 0);
             calendar.set(Calendar.MILLISECOND, 0);
             Date newShowDate = calendar.getTime();
             System.out.println(newShowDate);
    
            //12.获取特定格式的日期
             Calendar calendar =Calendar.getInstance();
             DateTool dt = new DateTool();
             String showDate = dt.format("MMM d, yyyy", calendar.getTime());
             System.out.println(showDate);
    
            Date date = new Date();
            DateFormat shortDateFormat = DateFormat.getDateTimeInstance(DateFormat.SHORT,DateFormat.SHORT);
            DateFormat mediumDateFormat = DateFormat.getDateTimeInstance(DateFormat.MEDIUM,DateFormat.MEDIUM);
            DateFormat longDateFormat = DateFormat.getDateTimeInstance(DateFormat.LONG,DateFormat.LONG);
            DateFormat fullDateFormat = DateFormat.getDateTimeInstance(DateFormat.FULL,DateFormat.FULL);
            //7/14/16 6:18 PM
            System.out.println(shortDateFormat.format(date));
            //Jue 14, 2016 6:18:20 PM
            System.out.println(mediumDateFormat.format(date));
            //Jue 14, 2016 6:18:20 PM CST
            System.out.println(longDateFormat.format(date));
            //Monday, Jue 14, 2016 6:18:20 PM CST
            System.out.println(fullDateFormat.format(date));
        }
    }